High-performance deep-blue phosphorescent organic light-emitting diodes enabled by a platinum(II) emitter

High-performance deep-blue phosphorescent organic light-emitting diodes enabled by a platinum(II) emitter | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article High-performance deep-blue phosphorescent organic light-emitting diodes enabled by a platinum(II) emitter Guijie Li, Qingshan Chu, Huanhuan Yao, Kongwu Wu, Yuan-Bin She This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5009247/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 09 Jul, 2025 Read the published version in Nature Photonics → Version 1 posted You are reading this latest preprint version Abstract Organic light-emitting diodes (OLEDs) represent a revolutionary technology, that has been successfully commercialized in full-color displays. However, this technology is still severely limited by the low efficiency of blue OLEDs. Developing high-performance blue OLEDs is a major challenge, and emitters are critical for overcoming this issue. Herein, we developed a strategy to design phosphorescent Pt(II) complexes with a locally excited-dominated character and a rigid 3D geometry to suppress intermolecular interactions, enabling robust deep-blue emitters. A bottom-emitting OLED realized a high color purity with a full-width at half-maximum (FWHM) of 17.1 nm, a high maximum brightness of 48968 cd/m2, and high external quantum efficiencies (EQEs) of 31.3%, 27.0%, and 23.6% at 1000, 5000, and 10000 cd/m2, respectively. A top-emitting OLED achieved an enhanced color purity (FWHM = 13.1 nm, CIEy = 0.06), a low running voltage (3.9 V at 1000 cd/m2), and a maximum EQE of 49.5%, and maintained EQEs of 46.4%, 39.5%, and 34.3% at 1000, 5000, and 10000 cd/m2, respectively. The OLED also exhibited a maximum blue index (BI) of 468 cd A-1CIEy-1 and a long half-lifetime of 670 h at an initial luminance of 1000 cd/m2. This study provides a important strategy to develop high-performance deep-blue phosphorescent OLEDs. Physical sciences/Materials science/Materials for optics/Lasers, LEDs and light sources/Organic LEDs Physical sciences/Chemistry/Materials chemistry/Optical materials Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Organic light-emitting diodes (OLEDs) represent a revolutionary display technology with many advantages compared to liquid crystal display (LCD), including high resolution, wide viewing angle, high contrast and fast response. 1 OLEDs have been successfully commercialized in full-color displays for mobile phones, laptops, and televisions, and can also implemented in future virtual reality (VR) and augmented reality (AR) products; hence, they are gradually becoming the mainstream display technology. 2 Luminescent materials play a critical role in the performances of OLEDs. Among the three essential colors, high performance red and green OLEDs have been commercialized, whereas the commercialized blue fluorescent OLEDs still suffer from low efficiency, this is because the fluorescent materials are unable to harvest electrogenerated triplet excitons, which results in the blue OLED energy consumption to account for approximately 60% of the total energy consumption of the display. In the past three decades, several types of luminescent materials have been designed and exhibited the potential ability to harvest all the electrogenerated excitons, achieving high device efficiencies. 3–11 The color purity is another key criterion of blue OLEDs, which depends on the width of the emission spectrum and is typically measured by the full-width at half-maximum (FWHM). 2 Luminescent materials with small FWHM can enhance the efficiency of top-emitting OLEDs employed in commercial displays. The National Television System Committee (NTSC) specifies the Commission Internationale de l’Éclairage (CIE) coordinates of pure blue as (0.14, 0.08), whereas the corresponding standard of the European Broadcast Union (EBU) is (0.15, 0.06). Luminescent materials with high color purity would greatly facilitate the future development of high-end display electronics. Moreover, in order to meet the requirements of commercial large-size or outdoor displays, where the displays constantly operate at high brightness for a long time, the brightness has also become an important parameter for achieving high OLED performances; therefore, the operational lifetime of OLEDs is also vital for their commercial applications. Despite the great progress made in the past three decades, 12–24 it is still a major challenge to realize simultaneously highly efficient and stable deep-blue OLEDs with high color purity and brightness, and especially to achieve a CIE y value < 0.15 to meet commercialization requirements. Phosphorescent Pt(II) complexes exhibit strong spin-orbit coupling (SOC), due to the heavy atom effect; 25 this facilitates efficient intersystem crossing (ISC) from the lowest singlet (S 1 ) to triplet (T 1 ) states, which enables Pt(II) complexes to utilize all the electrogenerated singlet and triplet excitons and achieve high quantum efficiencies. 26,27 Moreover, the photophysical properties of the Pt(II) complexes can be efficiently regulated by tuning their ligand structures. 27,28 Compared to bidentate and tridentate ligands, Pt(II) complexes employing tetradentate ligands typically exhibit more rigid molecular geometries and suppressed structural deformations in the excited state, resulting in improved photophysical properties and device performances. 2,12,17,26–29 Therefore, tetradentate Pt(II) complexes have attracted great attention from both academia and industry. 17,30,31 However, many issues still exist and urgently need to be solved to meet the strict requirements of commercial applications. Narrowband Pt(II) complexes typically exhibit emission spectra with FWHM values of greater than 20 nm, together with a strong v 0-1 vibrational sideband, 2,12,17,27,28,32–38 which significantly reduce their color purity. Therefore, a key question is how to further narrow the intrinsic spectra of Pt(II) complexes and reduce vibrational sidebands to increase the color purity; other important challenges include limiting the spectral broadening caused by intermolecular interactions, 17,31 maintaining a high device efficiency under high brightness, and achieving a long operational lifetime. Results Molecular design and theoretical calculations The Pt(II) ion adopts dsp 2 hybridization, forming Pt(II) complexes with square-planar geometries (Fig. 1a); therefore, these complexes tend to undergo intermolecular π–π, Pt–Pt stacking or guest-host interactions, which typically result in broadened and redshifted emission spectra, triplet–triplet annihilation, decreased device efficiency at high luminescence, and even molecular degradation (Fig. 1a). 12,17,22,24 To overcome these issues, the molecular structure should be elaborately designed by assembling appropriate steric hindrance groups at appropriate molecular positions, in order to optimize the molecular geometry and suppress intermolecular interactions (Fig. 1b). Moreover, the excited-state properties of the Pt(II) complex should be also carefully tuned. As illustrated in Fig. 1c, Pt(II) complexes with dominant metal-to-ligand charge transfer ( 3 MLCT) character typically show a large shift in the equilibrium position of the excited state with respect to the ground state (S 0 ), resulting in Gaussian-type broad emission spectra and low color purities. 39–41 Therefore, the 3 MLCT state should be carefully tuned to a slightly higher position than the locally excited ( 3 LE) state; this enables the Pt(II) complex to possess a 3 LE-dominated excited state mixed with 3 MLCT character, where the 3 LE state is essential to ensure a small excited state transformation and a narrowband emission spectrum, and the 3 MLCT character facilitates a highly efficient ISC of S 1 → T 1 → S 0 to yield a high quantum efficiency, thus achieving both high quantum efficiency and excellent color purity. Early in 2014, we reported the first efficient deep-blue OLED with a maximum external quantum efficiency (EQE) > 20% and a CIE y value < 0.1, using an N -heterocyclic carbine (NHC)-based tetradentate Pt(II) complex, PtON7-dtb as emitter. 12 In 2022, Kim and co-workers designed a new Pt(II) complex, PtON-TBBI, with exceptionally long device lifetime and high quantum efficiency, which was the most advanced blue phosphorescent OLED up to that time. 17 In this study, we designed a robust emitter consisting of platinum(II) [6-(2,3-dihydro-3-(3,3'',5,5',5''-penta- tert -butyl-[1,1':3',1''-terphenyl]-2'-yl)-1 H -benzo[ d ]imidazol-1-ylidene-𝜅 C 2 )-1,2-phenylene-𝜅 C 1 ]oxy[9-(4- tert -butyltpyridin-2-yl-𝜅 N )-9 H -benzofuro[2,3- d ]carbazole-1,2-diyl-𝜅 C 1 ] (PtQS1) (Fig. 1d). First, in order to tune the excited-state properties and increase the 3 LE proportion in T 1 state, we assembled an extended π-conjugation benzofuro[3,2- c ]carbazole (BFCz) in PtQS1 to replace the carbazole moiety of PtON-TBBI; this would facilitate the reduction of the FWHM and improve the photophysical properties of PtQS1. Second, an extremely bulky 3,3'',5,5',5''-penta-tert-butyl-1,1':3',1''-terphenyl group (PTBTP, colored in gray in Fig. 1d) was introduced and bonded with the NHC moiety; two bulky 3,5-di- tert -butylphenyl (dtBuPh) groups were attached to the ortho -positions of the 4- tert -butylphenyl moiety, this would make the PTBTP moiety perpendicular to the molecular core (colored in light blue), and endow PtQS1 with a three-dimensional (3D) configuration, which would suppress intermolecular interactions. Third, the four tert -butyl groups on the dtBuPh moiety could restrict the free rotations of the C Ph –C Ph and C Ph –N NHC bonds, resulting in enhanced molecular rigidity and reduced vibrations/rotations; at the same time, they could also reduce the conjugation between the three phenyl groups and the NHC moiety, which could avoid affecting the excited-state properties of PtQS1 and eliminate the redshift of the emission spectrum. Finally, the extended π-conjugation and increased molecular rigidity of PtQS1 would also be beneficial to improve the quantum efficiency. 42 We performed density functional theory (DFT) calculations, and the results are illustrated in Fig. 1e and Supplementary Fig. 1. Compared to PtON-TBBI, PtQS1 exhibited a lower-lying highest occupied molecular orbital (HOMO, ‒4.64 vs. ‒4.67 eV) level, and a similar lowest unoccupied molecular orbital (LUMO, ‒1.20 vs. ‒1.21 eV) level, resulting in a slightly larger energy gap ( E g , 3.44 vs. 3.46 eV). PtQS1 and PtON-TBBI exhibited similar HOMO and LUMO distributions. Notably, PtQS1 showed significantly delocalized distributions on the BFCz moiety, especially for the LUMO, but nearly no HOMO and LUMO components on the PTBTP moiety; these results indicate that the BFCz moiety would greatly affect the excited state of PtQS1, while PTBTP had almost no effect. This analysis was supported by time-dependent DFT (TD-DFT) calculations and natural transition orbital (NTO) analyses (Fig. 1f). PtQS1 had a 3 LE state localized on the BFCz moiety, with a 42.4% contribution of the T 1 electron on the π BFCz * orbital, which was nearly twofold larger than that on the π Cz * orbital in PtON-TBBI (19.8%). In contrast, the contribution of T 1 electrons on the π NHC-Ph * orbital significantly decreased from 36.6% in PtON-TBBI to 18.8% in PtQS1, which was assigned to an inter-ligand charge transfer ( 3 ILCT, π NHC * → π Ph ) state; the 3 ILCT character would result in a structureless and broadened emission spectrum 43 . Moreover, PtQS1 still maintained a 10.6% 3 MLCT (π Py * → d Pt π Ph ) character, as estimated from the decrease in the electron distribution on the Pt atom. 44 These results reveal markedly increased 3 LE and decreased 3 ILCT characters in the T 1 state of PtQS1. Synthesis, characterization, and thermal stability The large-scale synthesis of PtQS1 is an important task to further investigate its photophysical and electroluminescent properties. Therefore, we developed an efficient synthetic route (Fig. 2a), and the detailed synthetic procedures are provided in the Supplementary Information. The coupling of 4-( tert -butyl)-2-chloropyridine with 3-methoxy-5 H -benzofuro[3,2- c ]carbazole (1) through a Pd(0)-catalyzed C‒N bond cross-coupling reaction gave 5-(4-( tert -butyl)pyridin-2-yl)-3-methoxy-5 H -benzofuro[3,2- c ]carbazole (2) in 81% yield and gram-scale quantities. Compound 2 was then demethylated using pyridine hydrochloride (Py·HCl) to give the key intermediate phenol 3 in excellent yield (94%). After that, phenol 3 was further coupled with 1-bromo-3-chlorobenzene through a Cu(I)-catalyzed C‒O bond cross-coupling reaction to afford intermediate 4 in 80% yield. Further coupling of intermediate 4 with N 1 -(3,3'',5,5',5''-penta- tert -butyl-[1,1':3',1''-terphenyl]-2'-yl)benzene-1,2-diamine (5) catalyzed by Pd(0) catalyst to generate an electron-rich diaryl diamine intermediate in 94% yield, which was not stable in air and tended to be oxidized by molecular oxygen; therefore, compound 5 needed to be rapidly purified and immediately subjected to the next cyclization reaction with triethyl orthoformate, affording the benzimidazolium ligand precursor LQS1 in 85% yield. Finally, the desired tetradentate Pt(II) complex PtQS1 was obtained in high yield (79%) and large-gram-scale quantity (24.49 g) through metalation of LQS1 using Pt(COD)Cl 2 [COD: (1 Z ,5 Z )-cycloocta-1,5-diene] in diethylene glycol dimethyl ether (DEDM) at 150 °C. More importantly, the present development of an efficient and large-scale synthetic route for PtCY1 would facilitate systematic studies of its photophysical properties and the fabrication of deep-blue OLEDs. All the intermediates, as well as LQS1 and PtQS1 were characterized by 1 H, 13 C nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry (HRMS); the corresponding details are reported in the Supplementary Information. Notably, in the 1 H NMR spectra of PtQS1, the four tert -butyl groups of dtBuPh exhibited two broad bands in the 0.0–1.5 ppm region in deuterated dimethyl sulfoxide (DMSO- d 6 ), as well as one broad band in the same region in deuterated chloroform (CDCl 3 ). These signals were very different from those of the tert -butyl groups in diamine 5 and LQS1, which displayed very sharp peaks. Moreover, broad bands were also observed in the aromatic region in both DMSO- d 6 and CDCl 3 . These results can be attributed to the huge steric hindrance effect between the dtBuPh groups and the molecular core, which suppresses the rapid and free rotation of the dtBuPh groups in the solutions. This analysis was supported by the X-ray diffraction structure of PtQS1 (Fig. 2b, Supplementary Table 1; CCDC: 2346824), where the 4-tBu-phenyl plane is almost perpendicular to the Ph/NHC plane. Furthermore, the dtBuPh groups result in PtQS1 adopting a three-dimensional geometry, rather than a planar configuration. These structural features endow PtQS1 with an enhanced molecular rigidity compared to PtON-TBBI, and also are beneficial for suppressing intermolecular interactions. Actually, no intermolecular π-π stacking interactions were observed in the crystal stacking structure (Supplementary Fig. 2), but are often reported for tetradentate Pt(II) complexes 27,45,46 . The thermal stability is an important factor for further purification through sublimation and OLED fabrication by thermal evaporation. Thermogravimetric analysis (TGA) showed that PtQS1 had high thermal stability, with the 5% weight loss temperature (Δ T 5% ) of 473 °C, and no decomposition was observed below 400 °C (Supplementary Fig. 3). Photophysical properties The absorption spectra of LQS1, PtQS1, and PtON-TBBI in dichloromethane at room temperature are compared in Fig. 3a. Based on TD-DFT calculations and NTO analysis, the absorption of PtQS1 mainly involved the HOMO, LUMO, and LUMO+1 orbitals (Supplementary Fig. 4 and Supplementary Table 2). The strong absorption bands below 320 nm (ε > 1.5 × 10 4 cm −1 M −1 ) of PtQS1 corresponded to allowed 1 (π–π*) transitions from π Ph →π NHC *. The relatively intense bands in the 340–425 nm region (ε > 5 × 10 3 cm −1 M −1 ) were attributed to 1 MLCT transitions from π Ph d Pt →π Py *, involving both the cyclometalating ligand and the Pt(II) ion. Compared to PtON-TBBI, PtQS1 exhibited larger molar extinction coefficients for all transitions, indicating an enhanced transition dipole moment. The photoluminescence (PL) spectra of PtON-TBBI and PtQS1 in 2-methyltetrahydrofuran (2-MeTHF) at 77 K and in dichloromethane at room temperature are shown in Figs. 3b and 3c. PtON-TBBI and PtQS1 showed similar low-temperature spectra, with sharp emission peak at 445.8 and 455.0 nm, indicating triplet energy levels ( E T1 ) of 2.78 and 2.73 eV, respectively (Supplementary Table 3). However, their room-temperature PL spectra were significantly different. PtON-TBBI exhibited a significantly broadened spectrum peaking at 456.0 nm with a FWHM value of 25.1 nm and a large Huang–Rhys factor ( S M ) of 0.467, as estimated from the height ratio of the v 0-1 to v 0-0 peak. 47 In comparison, PtQS1 still showed a much narrow spectrum peaking at 460.4 nm, with a FWHM value of only 17.1 nm and a small S M of 0.293, suggesting a significantly enhanced color purity. To the best of our knowledge, this is the first Pt(II) complex showing a narrow emission spectrum with S M < 0.300 in dichloromethane at room temperature. Moreover, PtQS1 also exhibited a slight red shift of 5.4 nm at room-temperature, which was much smaller than that of PtON-TBBI (10.2 nm), indicating an enhanced molecular rigidity and a small excited-state deformation of PtQS1. We also investigated solvatochromic effects (Fig. 3, Supplementary Figs. 5–8, Supplementary Table 4). The emission spectra exhibited a blue shift with increasing polarity of the solvents. This shift is attributed to the reduced dipole moment in the T 1 state (6.07 D) of PtQS1 compared to the S 0 state (8.67 D), as determined by the DFT calculations. In all solvents, ranging from non-polar n -hexane (dielectric constant ε = 1.90) to medium-polar ethyl acetate ( ε = 6.40) and highly polar N , N -dimethylformamide ( ε = 36.7), the emission spectra of PtQS1 shifted in a small region of 8.2 nm, indicating a very weak solvatochromic effect. Moreover, PtQS1 always exhibited narrow emission spectra with FWHM values of 11.4–18.4 nm and small S M values of 0.222–0.311, e.g. a FWHM value of only 11.4 nm with an S M of 0.224 in n -hexane; the separation between the v 0-1 and v 0-0 components was 1125–1322 cm –1 , indicating the presence of stretching vibrational modes (Supplementary Table 4). The FWHM and S M values exhibited a good linear relationship (Fig. 3d); moreover, both the FWHM and S M were exponentially correlated with the dielectric constants of the solvents (Supplementary Figs. 7 and 8). The weak solvatochromic effect, narrow emission spectra, and small S M values indicated the 3 LE dominated character of the T 1 state. The PL quantum efficiency ( Φ PL ) of a 8 wt.% PtQS1:65 wt.% SiCzCz:27 wt.% SiTrzCz2 film [where SiCzCz = 9-(3-(triphenylsilyl)phenyl)-9 H -3,9′-bicarbazole, and SiTrzCz2 = 9,9′-(6-(3-(triphenylsilyl)phenyl)-1,3,5-triazine-2,4-diyl)bis(9 H -carbazole)] was up to 99%, thus much higher than that of PtON-TBBI (89%) (Fig. 3e). Additionally, 5 wt.% PtQS1 showed a slightly longer excited-state lifetime ( τ ) of 2.96 μs compared to PtON-TBBI (2.01 μs), owing to the slightly decreased 3 MLCT character of its T 1 state. The significantly decreased FWHM and S M values, small solvatochromic effect, and enhanced quantum efficiency of PtQS1 revealed an increased 3 LE character of the T 1 state, an enhanced molecular rigidity, as well as suppressed molecular vibrations and nonradiative decays. These results indicate that the excited-state properties of Pt(II) complexes can be precisely controlled through rational molecular design. Device performance We then investigated the electroluminescence (EL) properties of a PtQS1-based device (Fig. 4). The HOMO and LUMO levels of PtQS1 were calculated from its redox potentials, as measured by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) (Supplementary Table 3, Supplementary Fig. 9). We fabricated a bottom-emitting device with the following structure: ITO/HATCN (20 nm)/TAPC (60 nm)/SiCzCz (5 nm)/8 wt.% PtQS1:65 wt.% SiCzCz:27 wt.% SiTrzCz2 (35 nm)/mSiTrz (5 nm)/50 wt.% mSiTrz:50 wt.% Liq (31 nm)/LiF (1.5 nm)/Al, where ITO = indium tin oxide, HATCN = 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene, TAPC = 1,1'-bis[4-(di- p -tolylamino)phenyl]cyclohexane, mSiTrz = 2-phenyl-4,6-bis(3-(triphenylsilyl)phenyl)-1,3,5-triazine, and Liq = lithium quinolin-8-olate. The energy level diagram and chemical structures of the materials are illustrated in Fig. 4a. SiCzCz and SiTrzCz2 were employed as p -type and n -type host materials, respectively; 17 moreover, SiCzCz and mSiTrz were used as electron and hole blocking layers, respectively, because the high HOMO level of SiCzCz and the deep LUMO level of mSiTrz could confine the excitons inside the emitting layer; TAPC and mSiTrz:Liq served as hole and electron transport layers, whereas HATCN and LiF acted as hole and electron injection layers, respectively; finally, ITO and Al were used as anode and cathode, respectively. The PtQS1-based device emitted deep-blue light and displayed an extremely narrow emission peak at 464 nm, with small FWHM and S M values of only 17.1 nm and 0.270, respectively, achieving CIE coordinates of (0.13, 0.11) (Fig. 4b). Particularly, no EL spectral broadening was observed, and the EL spectrum had the same FWHM as the PL spectrum in dichloromethane (Fig. 3c); moreover, the EL spectrum showed a further reduced S M . Previous work found that a square-planar Pt(II) complex and SiTrzCz2 with a deep LUMO level could generate an exciplex, leading to reduced color purity; 17,24 however, no exciplex emission was observed for the PtQS1-based device, because the bulky 3D configuration of PtQS1 suppressed the intermolecular interactions. The FWHM value of 17.1 nm was smaller than those of micro light-emitting diodes (microLEDs) and quantum-dot light-emitting diodes (QD-LEDs). 48–50 The device exhibited a low turn-on voltage of 2.4 V, a running voltage of 5.4 V at a practical luminance of 1000 cd/m 2 , and a maximum luminescence ( L max ) of 48968 cd/m 2 (Fig. 4c). It also achieved a maximum EQE of 35.5%, and could still reach an EQE of 31.3% at a practical luminance of 1000 cd/m 2 ; moreover, the EQE could be maintained at 27.0% and 23.6% at 5000 and 10000 cd/m 2 , respectively(Fig. 4d). Finally, the device also exhibited a maximum current efficiency (CE) of 30.7 cd/A, which still maintained at 27.1, 23.4, and 20.6 cd/A at 1000, 5000, and 10000 cd/m 2 , respectively(Fig. 4e). The high efficiency was attributed to the lower-lying T 1 state of PtQS1 (2.72 eV) compared to that of the SiCzCz:SiTrzCz2 exciplex host (2.84 eV) 17 , which enabled an efficient and complete energy transfer from the hosts to the dopant molecules. The low efficiency roll-off indicated reduced triplet–triplet and triplet–polaron annihilations, owing to the suppressed intermolecular interactions. The chemical structures of deep-blue emitters based on Pt(II) and Ir(III) complexes, and of multiple resonance (MR) deep-blue emitters based on organic boron-nitrogen (BN) compounds are shown in Supplementary Figs.10, 11, and 12, respectively; moreover, the device performances of their doped deep-blue phosphorescent OLEDs and MR-OLEDs with CIE y < 0.15 are summarized in Supplementary Tables 5–7; additionally, the device performances of the closely-watched deep-blue hyperfluorescence (HF)-OLEDs were summarized in Supplementary Table 8. To the best of our knowledge, the present system is the first deep-blue phosphorescent OLEDs with CIE y < 0.15 to achieve an FWHM value of < 20 nm (Supplementary Tables 5 and 6). Moreover, the PtQS1-based device achieved record-high EQEs at high luminance values of 1000, 5000, and 10000 cd/m 2 among reported deep-blue OLEDs with CIE y < 0.15, including phosphorescent OLEDs based on Pt(II) and Ir(III) complexes, BN-based MR-OLEDs, and also one of the best among HF-OLEDs (Fig. 4f and Supplementary Fig. 13). The L max of the PtQS1-based device (48968 cd/m 2 )also represents one of the highest luminance values among those reported for deep-blue OLEDs with CIE y < 0.15 (Fig. 4g). Based on the top-emitting architectures adopted by all commercial OLEDs, and also the narrow emission spectrum of the PtQS1-based device, we fabricated a top-emitting OLED using PtQS1 as emitter and compared it with a PtON-TBBI-based OLED; the corresponding device performances and materials are shown in Fig. 5 and Supplementary Fig. 14, respectively. The PtQS1 device showed a deep-blue emission peaking at 464 nm, read shifted by 5 nm compared to the PtON-TBBI device; however, the PtQS1 device achieved a much narrower spectrum, with a FWHM value of 13.1 nm and CIE coordinates of (0.13, 0.06) at 1000 cd/m 2 (Fig. 5a). These chromaticity coordinates meet the pure blue standards of NTSC and EBU, and are extremely close to the BT.2020 standard (0.131, 0.046). Moreover, the PtQS1 device also exhibited a low running voltage of 3.9 V at 1000 cd/m 2 , significantly lower than that of the PtON-TBBI device (4.3 V) (Fig. 5b). Importantly, the PtQS1 device showed a high maximum EQE of 49.5% at 147 cd/m 2 , which was 1.83 times that of the PtON-TBBI device; and still maintained EQEs of 46.4% and 39.5% at pratical luminance values of 1000 and 5000 cd/m 2 , respectively, which were 1.86 and 1.91 times higher than those of the PtON-TBBI device (Fig. 5c). Notably, the PtQS1 device could still achieve an EQE of 34.3% at a high luminance of 10000 cd/m 2 (Fig. 5c). This result indicated that the small FWHM of the emission spectrum could significantly enhance the efficiency of the top-emitting OLED. To our knowledge, the present PtQS1 device is the first deep-blue OLED with CIE y 30% at 10000 cd/m 2 . The blue index (BI) is a key parameter used to evaluate the performance of blue OLEDs in the industry, defined as the ratio of current efficiency to CIE y . 16,18 The PtQS1 device achieved a maximum BI value of up to 468 cd A –1 CIE y –1 with a small efficiency roll-off, and retained 438, 372, and 325 cd A –1 CIE y –1 at 1000, 5000, and 10000 cd/m 2 , respectively, representing significantly enhanced BI values compared to the PtON-TBBI device (Fig. 5d). The BI value of the PtQS1-based device is about twofold that of commercial deep-blue fluorescent OLEDs. We also investigated the light color stability and operational lifetime of the PtQS1 device. The emission peaks and FWHMs of the device remained basically unchanged within a wide range of practical brightness values, suggesting a high light color stability (Fig. 5e). Importantly, the PtQS1 device showed a long half-lifetime (defined as the time at which the luminance decays to 50% of the initial luminance) of 670 h at a L 0 of 1000 cd/m 2 , which was comparable to or even superior to that of the PtON-TBBI device (Fig. 5f). The highly efficient and stable PtQS1 device, with low running voltage and high color purity exhibits an excellent voerall performance reported to date for deep-blue OLEDs with CIE y < 0.10. These results suggest that a phosphorescent OLED with one Pt(II) emitter and two exciplex hosts could realize a high device performance for potentially practical applications, which could overcome the problems of four-source co-evaporation and the accurate control of the doping concentration of the light-emitting layer in the manufacturing process of OLED displays. Discussion The challenges associated with blue OLEDs severely hinder the development of the OLED field. The device efficiency, operational lifetime, color purity, brightness, and running voltage are all important parameters affecting commercial applications; however, simultaneously satisfying all the corresponding requirements represents a major challenge, and advanced emitters are critical to overcome the issue. In this study, we developed a novel strategy to design robust phosphorescent Pt(II) emitters. By incorporating an extended π-conjugation BFCz moiety to increase the proportion of 3 LE character in the T 1 state, and assembling a bulky PTBTP group to obtain a rigid 3D geometry to suppress intermolecular interactions, PtQS1 exhibited an extremely narrow emission spectrum (with an FWHM of 17.1 nm and a small S M of 0.295), along with a high quantum efficiency of 99%. We also developed a facile and efficient synthetic route, that enabled the large-scale production of PtQS1 and facilitated the investigation of device performance. The lower-lying T 1 state of PtQS1 (2.72 eV) compared to that of the SiCzCz:SiTrzCz2 exciplex host (2.84 eV) enabled efficient energy transfer from the host to the dopant molecules. A PtQS1-based bottom-emitting deep-blue OLED achieved a low turn-on voltage ( V on = 2.4 V), a high color purity (FWHM = 17.1 nm, S M = 0.270, CIE y = 0.11) and a high maximum brightness ( L max = 48968 cd/m 2 ); in addition, it exhibited high EQEs of 31.3%, 27.0%, and 23.6% at 1000, 5000, and 10000 cd/m 2 , respectively. This system is the first phosphorescent OLED with CIE y < 0.15 to achieve a FWHM of less than 20 nm. Because of its narrow EL spectrum, a PtQS1-based top-emitting OLED demonstrated further enhanced device performances through microcavity effects. The PtQS1-based OLED achieved an enhanced color purity (FWHM = 13.1 nm, CIE y = 0.06), a reduced running voltage ( V = 3.9 V at 1000 cd/m 2 ), along with a maximum EQE of 49.5%; additionally, it still maintained EQEs of 46.4%, 39.5%, and 34.3% at 1000, 5000, and 10000 cd/m 2 , respectively. The deep-blue OLED also exhibited a maximum BI of up to 468 cd A – 1 CIE y – 1 and a long half-lifetime of 670 h at a L 0 of 1000 cd/m 2 . This work presents a valuable molecular design strategy of robust Pt(II) emitters for developing high-performance deep-blue OLEDs. We envisage that our study may promote the development of deep-blue phosphorescent OLEDs suitable for real-world applications in displays and lighting. Declarations Data Availability The authors declare that the main data supporting the findings of this study are available within the article and its Supplementary Information files. Extra data are available from the corresponding author upon request. Crystallographic data for the structure reported in this Article have been deposited at the Cambridge Crystallographic Data Centre, under deposition numbers CCDC 2346824 (PtQS1). Copies of the data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/. Source data are provided with this paper. Acknowledgements This work was supported by the National Natural Science Foundation of China (Grant No. 22178319 and 22138011), the Zhejiang Province Vanguard Goose-Leading Initiative (2024C01260). We thank Jiyong Liu from Zhejiang University for the help in the single crystal measurement and analysis. Author contributions G.L. and Y.S initiated and supervised the project. G.L. designed the material and analysed the data. Q.C. and H.Y. synthesized and characterized the Pt(II) emitters, host materials and performed the computational calculation. K.W. fabricated the devices. G.L. contributed to the manuscript writing. All authors discussed the progress of the research and reviewed the manuscript. Competing interests The authors declare no competing financial interests. References Forrest, S. R. The path to ubiquitous and low-cost organic electronic appliances on plastic. Nature . 428 , 911–918 (2004). Ha, J. M., Hur, S. H., Pathak, A., Jeong, J.-E. & Woo, H. Y. 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Stable and efficient quantum-dot light-emitting diodes based on solution-processed multilayer structures. Nat. Photon. 5 , 543–548 (2011). Won, Y.-H., Cho, O., Kim, T., Chung, D.-Y., Kim, T., Chung, H., Jang, H., Lee, J., Kim, D. & Jang, E. Highly efficient and stable InP/ZnSe/ZnS quantum dot light-emitting diodes. Nature. 575 , 634–638 (2019). Zhang, W., Li, B., Chang, C., Chen, F., Zhang, Q., Lin, Q., Wang, L., Yan, J., Wang, F., Chong, Y., Du, Z., Fan, F. & Shen, H. Stable and efficient pure blue quantum-dot LEDs enabled by inserting an anti-oxidation layer. Nat. Commun. 15 , 783 (2024). Methods Quantum Chemical Calculations The theoretical calculations were performed using Gaussian 16 package. Themolecular geometries of S 0 were optimized with the DFT method at the MN15 level. The DFT calculations were performed using a B3LYP function with a basis set of 6-31G(d) for C, H, O and N atoms; the LANL2DZ basis set with ECP was used for Pt atoms. X-ray Crystallography X-ray diffraction data were collected at 170 K on a Bruker D8 Venture diffractometer using graphite-monochromated Mo-Kα radiation ( λ = 0.71073 Å) from a rotating anode generator. Photophysical Measurements The absorption spectra were measured on a Hitachi U-3900 UV−VS Spectrometer. Steady state emission experiments were performed on HITACHI F-7000 spectrometer. Low temperature (77 K) emission spectra and lifetimes were measured in 2-MeTHF cooled with liquid nitrogen. Lifetime measurements and quantum efficiency were measured using an Edinburgh FS5 spectrofluorometer equipped with an integrating sphere. OLED Fabrication and Characterization Bottom-emitting devices were fabricated by vacuum thermal evaporation, and were tested outside glove box after encapsulation. Prior to deposition, the prepatterned ITO coated glass substrates were cleaned by subsequent sonication in deionized water, acetone, and isopropanol. The metal layer and organic layers were fabricated by vacuum thermal evaporation on the cleaned ITO glass substrate under vacuum (< 4 × 10 –4 Pa) with 4 Å/s deposition rate for aluminum cathode and 2 Å/s for organic layers. The device areas were 9 mm 2 (3 mm × 3 mm). The current density-voltage-luminance characteristics of OLEDs were measured using a Keithey 2400 Source meter and a Keithey 2000 Source multimeter equipped with a calibrated silicon photodiode. The EL spectra were recorded with a multichannel spectrometer (PMA12, Hamamatsu Photonics). Top-emitting OLEDs were fabricated and tested in R&D Evaporation System (OASIS-C-E4T1-PcG-2020, Choshu Industry Co., Ltd.). Additional Declarations There is NO Competing Interest. Supplementary Files PtQS1Checkcifreport.pdf PtQS1CIF.cif SourceData.zip Source Data SupplementaryInformation20240806.pdf Cite Share Download PDF Status: Published Journal Publication published 09 Jul, 2025 Read the published version in Nature Photonics → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5009247","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":350468306,"identity":"edc8a6e6-8df5-4b8e-8bc2-3e4017676935","order_by":0,"name":"Guijie Li","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4klEQVRIie3QsQrCMBCA4ZNCXA5cT1R8hUhBHURfw7GloKtjB4eAoJuu+hZ9hJOCLgXXjnXp7OikpuqcdhTMv7SB+7i0ADbbT1ZT0oMhNgC8z7EiIWwqTbgaeUcg9Xg10p0GapGF1HYvnLduMOpE7OSZifRSX18sIewzz4hh5kYsBtJI9pr4a02OqiCxHzEKKicPQncFBXmWky4VRBFK8SZcTiRe9becCCmBYJjIwD3Eom/espnnvftyNGnsEj8Nw3Fne17l5i0M4vt/0NNH/XRM88UWBU72ea1zyazNZrP9ay/10UlJqTdjnQAAAABJRU5ErkJggg==","orcid":"","institution":"Zhejiang University of Technology","correspondingAuthor":true,"prefix":"","firstName":"Guijie","middleName":"","lastName":"Li","suffix":""},{"id":350468307,"identity":"2ba3ee76-8b4f-4d95-9e6b-712fb097055f","order_by":1,"name":"Qingshan Chu","email":"","orcid":"","institution":"Zhejiang University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Qingshan","middleName":"","lastName":"Chu","suffix":""},{"id":350468308,"identity":"69314a44-9224-46d2-9894-a43c4ef98290","order_by":2,"name":"Huanhuan Yao","email":"","orcid":"","institution":"Zhejiang University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Huanhuan","middleName":"","lastName":"Yao","suffix":""},{"id":350468309,"identity":"c22be96e-a994-4f0c-a922-85f1cf51a13c","order_by":3,"name":"Kongwu Wu","email":"","orcid":"","institution":"Zhejiang University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Kongwu","middleName":"","lastName":"Wu","suffix":""},{"id":350468310,"identity":"aae5b6d8-1405-4e99-ad85-e569856f346b","order_by":4,"name":"Yuan-Bin She","email":"","orcid":"","institution":"Zhejiang University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Yuan-Bin","middleName":"","lastName":"She","suffix":""}],"badges":[],"createdAt":"2024-08-31 13:45:09","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5009247/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5009247/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41566-025-01706-0","type":"published","date":"2025-07-09T04:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":64188890,"identity":"a4e3059d-ef6b-4760-8dae-6a802a56fcd7","added_by":"auto","created_at":"2024-09-09 17:21:00","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":3432415,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMolecular design and theoretical calculations. a\u003c/strong\u003e Square-planar 2D configuration of conventional Pt(II) complex and its geometry-enabled intermolecular stacking. \u003cstrong\u003eb\u003c/strong\u003e Molecular geometry of Pt(II) complex with bulky 3D configuration designed in this study. \u003cstrong\u003ec\u003c/strong\u003e Potential energy curves of vibronic coupling between S\u003csub\u003e0\u003c/sub\u003e and T\u003csub\u003e1\u003c/sub\u003e states illustrating the design of broadband and narrowband Pt(II) complexes \u003cem\u003evia\u003c/em\u003e regulation of their excited-state properties. \u003csup\u003e3\u003c/sup\u003eMLCT, metal-to-ligand charge transfer state; \u003csup\u003e3\u003c/sup\u003eLE, locally excited state (the high-lying intraligand charge-transfer (\u003csup\u003e3\u003c/sup\u003eILCT) state is omitted for clarity); \u003cem\u003ev\u003c/em\u003e, vibrational quantum number of S\u003csub\u003e0\u003c/sub\u003e state; \u003cem\u003ev\u003c/em\u003e′, vibrational quantum number of T\u003csub\u003e1 \u003c/sub\u003estate; \u003cem\u003er\u003c/em\u003e, nuclear displacement between S\u003csub\u003e0\u003c/sub\u003e and T\u003csub\u003e1\u003c/sub\u003e states. \u003cstrong\u003ed\u003c/strong\u003e Illustration of molecular design of PtQS1 adopted in this study. PTBTP, 3,3'',5,5',5''-penta-tert-butyl-1,1':3',1''-terphenyl (colored in gray). \u003cstrong\u003ee\u003c/strong\u003e DFT-calculated frontier molecular orbital distributions, energy levels, and energy band gaps (\u003cem\u003eE\u003c/em\u003e\u003csub\u003eg\u003c/sub\u003e) of PtON-TBBI and PtQS1. \u003cstrong\u003ef\u003c/strong\u003e Comparison of NTO analyses of T\u003csub\u003e1\u003c/sub\u003e states for PtON-TBBI and PtQS1. Ph-NHC, phenyl \u003cem\u003eN\u003c/em\u003e-heterocyclic carbene; Py, pyridine; Cz, carbazole; BFCz, benzofuro[3,2-\u003cem\u003ec\u003c/em\u003e]carbazole.\u003c/p\u003e","description":"","filename":"image1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5009247/v1/e7d6bb28044864c4aaf4e2d7.jpg"},{"id":64189148,"identity":"993607b9-8409-4c1a-ab41-095a4ea4438b","added_by":"auto","created_at":"2024-09-09 17:29:00","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":2534819,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSynthesis and characterization of PtQS1.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e Synthetic route of PtQS1. \u003cstrong\u003eb\u003c/strong\u003e ORTEP drawings of single-crystal X-ray diffraction molecular structure of PtQS1 (CCDC 2346824); hydrogen atoms are omitted for clarity.\u003c/p\u003e","description":"","filename":"image2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5009247/v1/56646c512e5f50801a8d6394.jpg"},{"id":64188889,"identity":"2ea407b9-5018-4f82-8195-ffb2830f498d","added_by":"auto","created_at":"2024-09-09 17:21:00","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":2590424,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePhotophysical properties of PtQS1.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e Absorption spectra of LQS1, PtQS1, and PtON-TBBI at room temperature in dichloromethane. \u003cstrong\u003eb\u003c/strong\u003e, \u003cstrong\u003ec\u003c/strong\u003e PL spectra of PtQS1 and PtON-TBBI at 77 K in 2-methyltetrahydrofuran, and at room temperature in dichloromethane. FWHM, full-width at half-maximum; \u003cem\u003eS\u003c/em\u003e\u003csub\u003eM\u003c/sub\u003e, Huang–Rhys factor. \u003cstrong\u003ed\u003c/strong\u003e Relationship between FWHM and \u003cem\u003eS\u003c/em\u003e\u003csub\u003eM\u003c/sub\u003e of PtQS1 in various solvents.\u003cstrong\u003e e\u003c/strong\u003e Transient decay curves of thermally evaporated 8 wt.% emitter:65 wt.% SiCzCz:27 wt.% SiTrzCz2 film (emitter: PtQS1 or PtON-TBBI). The quantum efficiency (\u003cem\u003eΦ\u003c/em\u003e) and excited state lifetime (\u003cem\u003eτ\u003c/em\u003e) of each film are shown in the inset.\u003c/p\u003e","description":"","filename":"image3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5009247/v1/e8f5b36556cc1e91b9cf441a.jpg"},{"id":64188895,"identity":"e61578b9-a11a-46d2-af9a-022b62103cf9","added_by":"auto","created_at":"2024-09-09 17:21:01","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":4192225,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eProperties of bottom-emitting OLED.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e Energy level diagram of OLED and chemical structures of component materials. \u003cstrong\u003eb\u003c/strong\u003e EL spectrum of 8 wt.% PtQS1-doped deep-blue OLED at 1000 cd/m\u003csup\u003e2\u003c/sup\u003e.\u003cstrong\u003e \u003c/strong\u003eInset: electroluminescence of deep-blue OLED.\u003cstrong\u003e c\u003c/strong\u003e Current density–voltage–luminance (\u003cem\u003eJ\u003c/em\u003e–\u003cem\u003eV\u003c/em\u003e–\u003cem\u003eL\u003c/em\u003e) curves.\u003cstrong\u003e d\u003c/strong\u003e External quantum efficiency \u003cem\u003evs.\u003c/em\u003e luminance (EQE–\u003cem\u003eL\u003c/em\u003e) curve. \u003cstrong\u003ee\u003c/strong\u003e Current efficiency \u003cem\u003evs.\u003c/em\u003e luminance (CE–\u003cem\u003eL\u003c/em\u003e) curve. \u003cstrong\u003ef\u003c/strong\u003e CIE\u003csub\u003ey\u003c/sub\u003e \u003cem\u003evs.\u003c/em\u003e EQE scatter plot at 10000 cd/m\u003csup\u003e2\u003c/sup\u003e for OLEDs based on Pt(II) and Ir(III) complexes, MR-OLEDs based on organic boron-nitrogen (BN) compounds, and BN-based hyperfluorescence (HF)-OLEDs with CIE\u003csub\u003ey \u003c/sub\u003e\u0026lt; 0.15. The maximum brightness values of representative OLEDs are indicated in parentheses. \u003cstrong\u003eg\u003c/strong\u003e CIE\u003csub\u003ey\u003c/sub\u003e \u003cem\u003evs.\u003c/em\u003e maximum brightness scatter plot for various deep-blue OLEDs with CIE\u003csub\u003ey \u003c/sub\u003e\u0026lt; 0.15. The EQE (%) of representative OLEDs at 1000, 5000, and 10000 cd/m\u003csup\u003e2\u003c/sup\u003e are indicated in parentheses.\u003c/p\u003e","description":"","filename":"image4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5009247/v1/86916f6ae24ec1dc3d867134.jpg"},{"id":64188894,"identity":"b0b4593e-c742-4855-8c4c-cc8a8025eef7","added_by":"auto","created_at":"2024-09-09 17:21:00","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":2780275,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eProperties of top-emitting OLED.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e EL spectra of 8 wt.% PtQS1 and 8 wt.% PtON-TBBI doped-OLEDs at 1000 cd/m\u003csup\u003e2\u003c/sup\u003e. \u003cstrong\u003eb\u003c/strong\u003e \u003cem\u003eJ\u003c/em\u003e–\u003cem\u003eV\u003c/em\u003e–\u003cem\u003eL\u003c/em\u003e curves. \u003cstrong\u003ec\u003c/strong\u003e EQE–\u003cem\u003eL\u003c/em\u003e curves. \u003cstrong\u003ed\u003c/strong\u003e Blue index (BI) \u003cem\u003evs.\u003c/em\u003e luminance curves. \u003cstrong\u003ee\u003c/strong\u003e Wavelength–luminance–FWHM curves of 8 wt.% PtQS1 doped-OLED. \u003cstrong\u003ef\u003c/strong\u003e Operational lifetimes of deep-blue OLEDs at an initial luminance (\u003cem\u003eL\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e) of 1000 cd/m\u003csup\u003e2\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"image5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5009247/v1/93a726bf451218759a7a3176.jpg"},{"id":86402917,"identity":"60731de3-474e-4065-b0d2-274fbc48c923","added_by":"auto","created_at":"2025-07-10 09:15:29","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":16415817,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5009247/v1/cc8b5530-0b26-4cbf-a430-041611c92324.pdf"},{"id":64189400,"identity":"ba97151b-df3e-42da-9897-44e2b200fb2d","added_by":"auto","created_at":"2024-09-09 17:37:00","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":101856,"visible":true,"origin":"","legend":"","description":"","filename":"PtQS1Checkcifreport.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5009247/v1/c0a0de2c975a318af8346fef.pdf"},{"id":64188897,"identity":"2313bc03-1b0c-492d-9a1f-88e4b3dc0f75","added_by":"auto","created_at":"2024-09-09 17:21:01","extension":"cif","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":3024369,"visible":true,"origin":"","legend":"","description":"","filename":"PtQS1CIF.cif","url":"https://assets-eu.researchsquare.com/files/rs-5009247/v1/06e5c44be5ec5d66673bc053.cif"},{"id":64188896,"identity":"53de9ab5-dbb6-45bb-ad83-196940f4e8ca","added_by":"auto","created_at":"2024-09-09 17:21:01","extension":"zip","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":876117,"visible":true,"origin":"","legend":"Source Data","description":"","filename":"SourceData.zip","url":"https://assets-eu.researchsquare.com/files/rs-5009247/v1/0d00fc699fe03dd54a9d1cee.zip"},{"id":64188898,"identity":"1300a998-3a5f-43ac-9b49-e6d6e7e1e9db","added_by":"auto","created_at":"2024-09-09 17:21:01","extension":"pdf","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":5391759,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryInformation20240806.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5009247/v1/f96f300055e13434b235a052.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"High-performance deep-blue phosphorescent organic light-emitting diodes enabled by a platinum(II) emitter","fulltext":[{"header":"Introduction","content":"\u003cp\u003eOrganic light-emitting diodes (OLEDs) represent a revolutionary display technology with many advantages compared to liquid crystal display (LCD), including high resolution, wide viewing angle, high contrast and fast response.\u003csup\u003e1\u003c/sup\u003e OLEDs have been successfully commercialized in full-color displays for mobile phones, laptops, and televisions, and can also implemented in future virtual reality (VR) and augmented reality (AR) products; hence, they are gradually becoming the mainstream display technology.\u003csup\u003e2\u003c/sup\u003e Luminescent materials play a critical role in the performances of OLEDs. Among the three essential colors, high performance red and green OLEDs have been commercialized, whereas the commercialized blue fluorescent OLEDs still suffer from low efficiency, this is because the fluorescent materials are unable to harvest electrogenerated triplet excitons, which results in the blue OLED energy consumption to account for approximately 60% of the total energy consumption of the display. In the past three decades, several types of luminescent materials have been designed and exhibited the potential ability to harvest all the electrogenerated excitons, achieving high device efficiencies.\u003csup\u003e3\u0026ndash;11\u003c/sup\u003e The color purity is another key criterion of blue OLEDs, which depends on the width of the emission spectrum and is typically measured by the full-width at half-maximum (FWHM).\u003csup\u003e2\u003c/sup\u003e Luminescent materials with small FWHM can enhance the efficiency of top-emitting OLEDs employed in commercial displays. The National Television System Committee (NTSC) specifies the Commission Internationale de l\u0026rsquo;\u0026Eacute;clairage (CIE) coordinates of pure blue as (0.14, 0.08), whereas the corresponding standard of the European Broadcast Union (EBU) is (0.15, 0.06). Luminescent materials with high color purity would greatly facilitate the future development of high-end display electronics. Moreover, in order to meet the requirements of commercial large-size or outdoor displays, where the displays constantly operate at high brightness for a long time, the brightness has also become an important parameter for achieving high OLED performances; therefore, the operational lifetime of OLEDs is also vital for their commercial applications. Despite the great progress made in the past three decades,\u003csup\u003e12\u0026ndash;24\u003c/sup\u003e it is still a major challenge to realize simultaneously highly efficient and stable deep-blue OLEDs with high color purity and brightness, and especially to achieve a CIE\u003csub\u003ey\u003c/sub\u003e value\u0026nbsp;\u0026lt;\u0026nbsp;0.15 to meet commercialization requirements.\u003c/p\u003e\n\u003cp\u003ePhosphorescent Pt(II) complexes exhibit strong spin-orbit coupling (SOC), due to the heavy atom effect;\u003csup\u003e25\u003c/sup\u003e this facilitates efficient intersystem crossing (ISC) from the lowest singlet (S\u003csub\u003e1\u003c/sub\u003e) to triplet (T\u003csub\u003e1\u003c/sub\u003e)\u0026nbsp;states, which enables Pt(II) complexes to utilize all the\u0026nbsp;electrogenerated\u0026nbsp;singlet and triplet\u0026nbsp;excitons\u0026nbsp;and achieve high quantum efficiencies.\u003csup\u003e26,27\u003c/sup\u003e Moreover, the\u0026nbsp;photophysical properties of the Pt(II) complexes can be efficiently regulated by tuning their ligand structures.\u003csup\u003e27,28\u003c/sup\u003e Compared to bidentate and tridentate ligands, Pt(II) complexes employing tetradentate ligands typically exhibit more rigid molecular geometries and suppressed structural deformations in the excited state, resulting in improved photophysical properties and device performances.\u003csup\u003e2,12,17,26\u0026ndash;29\u003c/sup\u003e Therefore, tetradentate Pt(II) complexes have attracted great attention from both academia and industry.\u003csup\u003e17,30,31\u003c/sup\u003e However, many issues still exist and urgently need to be solved to meet the strict requirements of commercial applications. Narrowband Pt(II) complexes typically exhibit emission spectra with FWHM values of greater than 20 nm, together with a strong \u003cem\u003ev\u003c/em\u003e\u003csub\u003e0-1\u003c/sub\u003e vibrational sideband,\u003csup\u003e2,12,17,27,28,32\u0026ndash;38\u003c/sup\u003e which significantly reduce their color purity. Therefore, a key question is how to further narrow the intrinsic spectra of Pt(II) complexes and reduce vibrational sidebands to increase the color purity; other important challenges include limiting the spectral broadening caused by intermolecular interactions,\u003csup\u003e17,31\u003c/sup\u003e maintaining a high device efficiency under high brightness, and achieving a long operational lifetime.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cstrong\u003eMolecular design and theoretical calculations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Pt(II) ion adopts dsp\u003csup\u003e2\u003c/sup\u003e hybridization, forming Pt(II) complexes with square-planar geometries\u0026nbsp;(Fig. 1a); therefore, these complexes tend to undergo intermolecular \u0026pi;\u0026ndash;\u0026pi;, Pt\u0026ndash;Pt stacking or guest-host interactions, which typically result in broadened and redshifted emission spectra, triplet\u0026ndash;triplet annihilation, decreased device efficiency at high luminescence, and even molecular degradation\u0026nbsp;(Fig. 1a).\u003csup\u003e12,17,22,24\u003c/sup\u003e To overcome these issues, the molecular structure should be elaborately designed by assembling appropriate steric hindrance groups at appropriate molecular positions, in order to optimize the molecular geometry and suppress intermolecular interactions\u0026nbsp;(Fig. 1b). Moreover, the excited-state properties of the Pt(II) complex should be also carefully tuned. As illustrated in\u0026nbsp;Fig. 1c, Pt(II) complexes with dominant metal-to-ligand charge transfer (\u003csup\u003e3\u003c/sup\u003eMLCT) character typically show a large shift in the equilibrium position of the excited state with respect to the ground state (S\u003csub\u003e0\u003c/sub\u003e), resulting in Gaussian-type broad emission spectra and low color purities.\u003csup\u003e39\u0026ndash;41\u003c/sup\u003e Therefore, the \u003csup\u003e3\u003c/sup\u003eMLCT state should be carefully tuned to a slightly higher position than the\u0026nbsp;locally excited (\u003csup\u003e3\u003c/sup\u003eLE) state; this enables the Pt(II) complex to possess a \u003csup\u003e3\u003c/sup\u003eLE-dominated\u0026nbsp;excited state mixed with \u003csup\u003e3\u003c/sup\u003eMLCT character, where the\u0026nbsp;\u003csup\u003e3\u003c/sup\u003eLE state is essential to ensure a small excited state transformation and a narrowband emission spectrum, and the \u003csup\u003e3\u003c/sup\u003eMLCT character facilitates a highly efficient ISC of S\u003csub\u003e1\u0026nbsp;\u003c/sub\u003e\u0026rarr;\u0026nbsp;T\u003csub\u003e1\u0026nbsp;\u003c/sub\u003e\u0026rarr;\u0026nbsp;S\u003csub\u003e0\u003c/sub\u003e to yield a high quantum efficiency, thus achieving both high quantum efficiency and excellent color purity.\u003c/p\u003e\n\u003cp\u003eEarly in 2014, we reported\u0026nbsp;the first efficient deep-blue OLED with a maximum external quantum efficiency (EQE) \u0026gt; 20% and a CIE\u003csub\u003ey\u003c/sub\u003e value \u0026lt; 0.1, using an \u003cem\u003eN\u003c/em\u003e-heterocyclic carbine (NHC)-based tetradentate Pt(II) complex, PtON7-dtb as emitter.\u003csup\u003e12\u003c/sup\u003e In 2022, Kim and co-workers designed a new Pt(II) complex, PtON-TBBI, with exceptionally long device lifetime and high quantum efficiency, which was the most advanced blue phosphorescent OLED up to that time.\u003csup\u003e17\u003c/sup\u003e In this study, we designed a robust emitter consisting of platinum(II) [6-(2,3-dihydro-3-(3,3\u0026apos;\u0026apos;,5,5\u0026apos;,5\u0026apos;\u0026apos;-penta-\u003cem\u003etert\u003c/em\u003e-butyl-[1,1\u0026apos;:3\u0026apos;,1\u0026apos;\u0026apos;-terphenyl]-2\u0026apos;-yl)-1\u003cem\u003eH\u003c/em\u003e-benzo[\u003cem\u003ed\u003c/em\u003e]imidazol-1-ylidene-𝜅\u003cem\u003eC\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e)-1,2-phenylene-𝜅\u003cem\u003eC\u003c/em\u003e\u003csup\u003e1\u003c/sup\u003e]oxy[9-(4-\u003cem\u003etert\u003c/em\u003e-butyltpyridin-2-yl-𝜅\u003cem\u003eN\u003c/em\u003e)-9\u003cem\u003eH\u003c/em\u003e-benzofuro[2,3-\u003cem\u003ed\u003c/em\u003e]carbazole-1,2-diyl-𝜅\u003cem\u003eC\u003c/em\u003e\u003csup\u003e1\u003c/sup\u003e] (PtQS1) (Fig. 1d). First, in order to tune the excited-state properties and increase the \u003csup\u003e3\u003c/sup\u003eLE proportion in T\u003csub\u003e1\u003c/sub\u003e state, we assembled an extended \u0026pi;-conjugation benzofuro[3,2-\u003cem\u003ec\u003c/em\u003e]carbazole (BFCz) in PtQS1 to replace the carbazole moiety of PtON-TBBI; this would facilitate the reduction of the FWHM and improve the photophysical properties of PtQS1. Second, an extremely bulky 3,3\u0026apos;\u0026apos;,5,5\u0026apos;,5\u0026apos;\u0026apos;-penta-tert-butyl-1,1\u0026apos;:3\u0026apos;,1\u0026apos;\u0026apos;-terphenyl group (PTBTP, colored in gray in Fig. 1d) was introduced and bonded with the NHC moiety; two bulky 3,5-di-\u003cem\u003etert\u003c/em\u003e-butylphenyl (dtBuPh) groups were attached to the \u003cem\u003eortho\u003c/em\u003e-positions of the 4-\u003cem\u003etert\u003c/em\u003e-butylphenyl moiety, this would make the PTBTP moiety perpendicular to the molecular core (colored in light blue), and endow PtQS1 with a three-dimensional (3D) configuration, which would suppress intermolecular interactions. Third, the four \u003cem\u003etert\u003c/em\u003e-butyl groups on the dtBuPh moiety could restrict the free rotations of the C\u003csub\u003ePh\u003c/sub\u003e\u0026ndash;C\u003csub\u003ePh\u003c/sub\u003e and C\u003csub\u003ePh\u003c/sub\u003e\u0026ndash;N\u003csub\u003eNHC\u003c/sub\u003e bonds, resulting in enhanced molecular rigidity and reduced vibrations/rotations; at the same time, they could also reduce the conjugation between the three phenyl groups and the NHC moiety, which could avoid affecting the excited-state properties of PtQS1 and eliminate the redshift of the emission spectrum. Finally, the extended \u0026pi;-conjugation and increased molecular rigidity of PtQS1 would also be beneficial to improve the quantum efficiency.\u003csup\u003e42\u0026nbsp;\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eWe performed density functional theory (DFT) calculations, and the results are illustrated in Fig. 1e and Supplementary Fig. 1. Compared to PtON-TBBI, PtQS1 exhibited a lower-lying highest occupied molecular orbital (HOMO, ‒4.64 \u003cem\u003evs.\u003c/em\u003e ‒4.67 eV) level, and a similar lowest unoccupied molecular orbital (LUMO, ‒1.20 \u003cem\u003evs.\u003c/em\u003e ‒1.21 eV) level, resulting in a slightly larger energy gap (\u003cem\u003eE\u003c/em\u003e\u003csub\u003eg\u003c/sub\u003e, 3.44 \u003cem\u003evs.\u003c/em\u003e 3.46 eV). PtQS1 and PtON-TBBI exhibited similar HOMO and LUMO distributions. Notably, PtQS1 showed significantly delocalized distributions on the BFCz moiety, especially for the LUMO, but nearly no HOMO and LUMO components on the PTBTP moiety; these results indicate that the BFCz moiety would greatly affect the excited state of PtQS1, while PTBTP had almost no effect. This analysis was supported by time-dependent DFT (TD-DFT) calculations and natural transition orbital (NTO) analyses (Fig. 1f). PtQS1 had a \u003csup\u003e3\u003c/sup\u003eLE state localized on the BFCz moiety, with a 42.4% contribution of the T\u003csub\u003e1\u0026nbsp;\u003c/sub\u003eelectron on the \u0026pi;\u003csub\u003eBFCz\u003c/sub\u003e* orbital, which was nearly twofold larger than that on the \u0026pi;\u003csub\u003eCz\u003c/sub\u003e* orbital in PtON-TBBI (19.8%). In contrast, the contribution of T\u003csub\u003e1\u0026nbsp;\u003c/sub\u003eelectrons on the \u0026pi;\u003csub\u003eNHC-Ph\u003c/sub\u003e* orbital significantly decreased from 36.6% in PtON-TBBI to 18.8% in PtQS1, which was assigned to an inter-ligand charge transfer (\u003csup\u003e3\u003c/sup\u003eILCT, \u0026pi;\u003csub\u003eNHC\u003c/sub\u003e*\u0026nbsp;\u0026rarr;\u0026nbsp;\u0026pi;\u003csub\u003ePh\u003c/sub\u003e) state; the \u003csup\u003e3\u003c/sup\u003eILCT character would result in a structureless and broadened emission spectrum\u003csup\u003e43\u003c/sup\u003e. Moreover, PtQS1 still maintained a 10.6% \u003csup\u003e3\u003c/sup\u003eMLCT (\u0026pi;\u003csub\u003ePy\u003c/sub\u003e*\u0026nbsp;\u0026rarr;\u0026nbsp;d\u003csub\u003ePt\u003c/sub\u003e\u0026pi;\u003csub\u003ePh\u003c/sub\u003e) character, as estimated from the decrease in the electron distribution on the Pt atom.\u003csup\u003e44\u003c/sup\u003e These results reveal markedly increased \u003csup\u003e3\u003c/sup\u003eLE and decreased \u003csup\u003e3\u003c/sup\u003eILCT characters in the T\u003csub\u003e1\u003c/sub\u003e state of PtQS1.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSynthesis, characterization, and thermal stability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe large-scale synthesis of PtQS1 is an important task to further investigate its photophysical and electroluminescent properties. Therefore, we developed an efficient synthetic route (Fig. 2a), and the detailed synthetic procedures are provided in the Supplementary Information. The coupling of 4-(\u003cem\u003etert\u003c/em\u003e-butyl)-2-chloropyridine with 3-methoxy-5\u003cem\u003eH\u003c/em\u003e-benzofuro[3,2-\u003cem\u003ec\u003c/em\u003e]carbazole (1) through a Pd(0)-catalyzed C‒N bond cross-coupling reaction gave 5-(4-(\u003cem\u003etert\u003c/em\u003e-butyl)pyridin-2-yl)-3-methoxy-5\u003cem\u003eH\u003c/em\u003e-benzofuro[3,2-\u003cem\u003ec\u003c/em\u003e]carbazole (2) in 81% yield and gram-scale quantities. Compound 2 was then demethylated using pyridine hydrochloride (Py\u0026middot;HCl) to give the key intermediate phenol 3 in excellent yield (94%). After that, phenol 3 was further coupled with 1-bromo-3-chlorobenzene through a Cu(I)-catalyzed C‒O bond cross-coupling reaction to afford intermediate 4 in 80% yield. Further coupling of intermediate 4 with \u003cem\u003eN\u003c/em\u003e\u003csup\u003e1\u003c/sup\u003e-(3,3\u0026apos;\u0026apos;,5,5\u0026apos;,5\u0026apos;\u0026apos;-penta-\u003cem\u003etert\u003c/em\u003e-butyl-[1,1\u0026apos;:3\u0026apos;,1\u0026apos;\u0026apos;-terphenyl]-2\u0026apos;-yl)benzene-1,2-diamine (5) catalyzed by Pd(0) catalyst to generate an electron-rich diaryl diamine intermediate in 94% yield, which was not stable in air and tended to be oxidized by molecular oxygen; therefore, compound 5 needed to be rapidly purified and immediately subjected to the next cyclization reaction with triethyl orthoformate, affording the benzimidazolium ligand precursor LQS1 in 85% yield. Finally, the desired tetradentate Pt(II) complex PtQS1 was obtained in high yield (79%) and large-gram-scale quantity (24.49 g) through metalation of LQS1 using Pt(COD)Cl\u003csub\u003e2\u003c/sub\u003e [COD: (1\u003cem\u003eZ\u003c/em\u003e,5\u003cem\u003eZ\u003c/em\u003e)-cycloocta-1,5-diene] in diethylene glycol dimethyl ether (DEDM) at 150 \u0026deg;C. More importantly, the present development of an efficient and large-scale synthetic route for PtCY1 would facilitate systematic studies of its photophysical properties and the fabrication of deep-blue OLEDs.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAll the intermediates, as well as LQS1 and PtQS1 were characterized by \u003csup\u003e1\u003c/sup\u003eH, \u003csup\u003e13\u003c/sup\u003eC nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry (HRMS); the corresponding details are reported in the Supplementary Information. Notably, in the \u003csup\u003e1\u003c/sup\u003eH NMR spectra of PtQS1, the four\u003cem\u003e\u0026nbsp;tert\u003c/em\u003e-butyl groups of dtBuPh exhibited two broad bands in the 0.0\u0026ndash;1.5 ppm region in deuterated dimethyl sulfoxide (DMSO-\u003cem\u003ed\u003c/em\u003e\u003csub\u003e6\u003c/sub\u003e), as well as\u0026nbsp;one broad band in the same region in\u0026nbsp;deuterated chloroform (CDCl\u003csub\u003e3\u003c/sub\u003e). These signals were very different from those of the \u003cem\u003etert\u003c/em\u003e-butyl groups in diamine 5 and LQS1, which displayed very sharp peaks. Moreover, broad bands were also observed in the aromatic region in both DMSO-\u003cem\u003ed\u003c/em\u003e\u003csub\u003e6\u003c/sub\u003e and CDCl\u003csub\u003e3\u003c/sub\u003e. These results can be attributed to the huge steric hindrance effect between the dtBuPh groups and the molecular core, which suppresses the rapid and free rotation of the dtBuPh groups in the solutions. This analysis was supported by the X-ray diffraction structure of PtQS1 (Fig. 2b, Supplementary Table 1; CCDC: 2346824), where the 4-tBu-phenyl plane is almost perpendicular to the Ph/NHC plane. Furthermore, the dtBuPh groups result in PtQS1 adopting a three-dimensional geometry, rather than a planar configuration. These structural features endow PtQS1 with an enhanced molecular rigidity compared to PtON-TBBI, and also are beneficial for suppressing intermolecular interactions. Actually, no intermolecular\u0026nbsp;\u0026pi;-\u0026pi; stacking interactions were observed in the crystal stacking structure (Supplementary Fig. 2), but are often reported for tetradentate Pt(II) complexes\u003csup\u003e27,45,46\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eThe thermal stability is an important factor for further purification through sublimation and OLED fabrication by thermal evaporation. Thermogravimetric analysis (TGA) showed that PtQS1\u0026nbsp;had high thermal stability, with the 5% weight loss temperature (\u0026Delta;\u003cem\u003eT\u003c/em\u003e\u003csub\u003e5%\u003c/sub\u003e) of 473 \u0026deg;C, and no decomposition was observed below 400 \u0026deg;C\u0026nbsp;(Supplementary Fig. 3).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePhotophysical properties\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe absorption spectra of LQS1, PtQS1, and PtON-TBBI in dichloromethane at\u0026nbsp;room temperature are compared in Fig. 3a. Based on TD-DFT calculations and NTO analysis, the absorption of PtQS1 mainly involved the HOMO, LUMO, and LUMO+1 orbitals\u0026nbsp;(Supplementary Fig. 4 and\u0026nbsp;Supplementary\u0026nbsp;Table 2). The strong absorption bands below 320 nm (\u0026epsilon; \u0026gt; 1.5 \u0026times; 10\u003csup\u003e4\u003c/sup\u003e cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e M\u003csup\u003e\u0026minus;1\u003c/sup\u003e) of PtQS1 corresponded to allowed \u003csup\u003e1\u003c/sup\u003e(\u0026pi;\u0026ndash;\u0026pi;*) transitions from \u0026pi;\u003csub\u003ePh\u003c/sub\u003e\u0026rarr;\u0026pi;\u003csub\u003eNHC\u003c/sub\u003e*. The relatively intense bands in the 340\u0026ndash;425 nm region (\u0026epsilon; \u0026gt; 5 \u0026times; 10\u003csup\u003e3\u003c/sup\u003e cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e M\u003csup\u003e\u0026minus;1\u003c/sup\u003e) were attributed to \u003csup\u003e1\u003c/sup\u003eMLCT transitions from \u0026pi;\u003csub\u003ePh\u003c/sub\u003ed\u003csub\u003ePt\u003c/sub\u003e\u0026rarr;\u0026pi;\u003csub\u003ePy\u003c/sub\u003e*, involving both the cyclometalating ligand and the Pt(II) ion. Compared to PtON-TBBI, PtQS1 exhibited larger molar extinction coefficients for all transitions, indicating an enhanced transition dipole moment.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe photoluminescence (PL) spectra of PtON-TBBI and PtQS1 in 2-methyltetrahydrofuran (2-MeTHF) at 77 K and in dichloromethane at room temperature are shown in Figs. 3b and 3c. PtON-TBBI and PtQS1 showed similar low-temperature spectra, with sharp emission peak at 445.8 and 455.0 nm, indicating triplet energy levels (\u003cem\u003eE\u003c/em\u003e\u003csub\u003eT1\u003c/sub\u003e) of 2.78 and 2.73 eV, respectively (Supplementary\u0026nbsp;Table 3). However, their room-temperature PL spectra were significantly different. PtON-TBBI exhibited a significantly broadened spectrum peaking at 456.0 nm with a FWHM value of 25.1 nm and a large\u0026nbsp;Huang\u0026ndash;Rhys factor (\u003cem\u003eS\u003c/em\u003e\u003csub\u003eM\u003c/sub\u003e) of\u0026nbsp;0.467, as estimated from the height ratio of the \u003cem\u003ev\u003c/em\u003e\u003csub\u003e0-1\u003c/sub\u003e to \u003cem\u003ev\u003c/em\u003e\u003csub\u003e0-0\u003c/sub\u003e peak.\u003csup\u003e47\u0026nbsp;\u003c/sup\u003eIn comparison, PtQS1 still showed a much narrow spectrum peaking at 460.4 nm, with a FWHM value of only 17.1 nm and a small \u003cem\u003eS\u003c/em\u003e\u003csub\u003eM\u003c/sub\u003e of\u0026nbsp;0.293, suggesting a significantly enhanced color purity. To the best of our knowledge, this is the first Pt(II) complex showing a narrow emission spectrum with \u003cem\u003eS\u003c/em\u003e\u003csub\u003eM\u003c/sub\u003e \u0026lt; 0.300 in dichloromethane at room temperature. Moreover, PtQS1 also exhibited a slight red shift of 5.4 nm at room-temperature, which was much smaller than that of PtON-TBBI (10.2 nm), indicating an enhanced molecular rigidity and a small excited-state deformation of PtQS1.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWe also investigated solvatochromic effects (Fig. 3,\u0026nbsp;Supplementary Figs. 5\u0026ndash;8,\u0026nbsp;Supplementary\u0026nbsp;Table 4). The emission spectra exhibited a blue shift with increasing polarity of the solvents. This shift is attributed to the reduced dipole moment in the T\u003csub\u003e1\u003c/sub\u003e state (6.07 D) of PtQS1 compared to the S\u003csub\u003e0\u003c/sub\u003e state (8.67 D), as determined by the DFT calculations. In all solvents, ranging from non-polar \u003cem\u003en\u003c/em\u003e-hexane (dielectric constant \u003cem\u003e\u0026epsilon;\u003c/em\u003e = 1.90) to medium-polar ethyl acetate (\u003cem\u003e\u0026epsilon;\u003c/em\u003e = 6.40) and highly polar \u003cem\u003eN\u003c/em\u003e,\u003cem\u003eN\u003c/em\u003e-dimethylformamide (\u003cem\u003e\u0026epsilon;\u003c/em\u003e = 36.7), the emission spectra of PtQS1 shifted in a small region of 8.2 nm, indicating a very weak solvatochromic effect. Moreover, PtQS1 always exhibited narrow emission spectra with\u0026nbsp;FWHM values of 11.4\u0026ndash;18.4 nm and small \u003cem\u003eS\u003c/em\u003e\u003csub\u003eM\u003c/sub\u003e values of\u0026nbsp;0.222\u0026ndash;0.311, e.g. a FWHM value of only 11.4 nm with an \u003cem\u003eS\u003c/em\u003e\u003csub\u003eM\u003c/sub\u003e of 0.224 in\u0026nbsp;\u003cem\u003en\u003c/em\u003e-hexane; the separation between the\u0026nbsp;\u003cem\u003ev\u003c/em\u003e\u003csub\u003e0-1\u003c/sub\u003e and \u003cem\u003ev\u003c/em\u003e\u003csub\u003e0-0\u003c/sub\u003e components was 1125\u0026ndash;1322 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e, indicating the presence of stretching vibrational modes\u0026nbsp;(Supplementary Table 4). The FWHM and \u003cem\u003eS\u003c/em\u003e\u003csub\u003eM\u003c/sub\u003e values exhibited a good linear relationship (Fig. 3d); moreover, both the FWHM and \u003cem\u003eS\u003c/em\u003e\u003csub\u003eM\u003c/sub\u003e were exponentially correlated with the\u0026nbsp;dielectric constants of the solvents (Supplementary Figs. 7 and 8). The weak solvatochromic effect, narrow emission spectra, and small\u0026nbsp;\u003cem\u003eS\u003c/em\u003e\u003csub\u003eM\u003c/sub\u003e values\u0026nbsp;indicated the \u003csup\u003e3\u003c/sup\u003eLE dominated character of the T\u003csub\u003e1\u003c/sub\u003e state.\u003c/p\u003e\n\u003cp\u003eThe PL quantum efficiency (\u003cem\u003e\u0026Phi;\u003c/em\u003e\u003csub\u003ePL\u003c/sub\u003e) of a 8 wt.% PtQS1:65 wt.% SiCzCz:27 wt.% SiTrzCz2\u0026nbsp;film [where\u0026nbsp;SiCzCz =\u0026nbsp;9-(3-(triphenylsilyl)phenyl)-9\u003cem\u003eH\u003c/em\u003e-3,9\u0026prime;-bicarbazole, and SiTrzCz2 = 9,9\u0026prime;-(6-(3-(triphenylsilyl)phenyl)-1,3,5-triazine-2,4-diyl)bis(9\u003cem\u003eH\u003c/em\u003e-carbazole)] was up to 99%, thus much higher than that of PtON-TBBI (89%) (Fig. 3e).\u0026nbsp;Additionally,\u0026nbsp;5 wt.% PtQS1 showed a slightly longer excited-state lifetime (\u003cem\u003e\u0026tau;\u003c/em\u003e) of 2.96 \u0026mu;s compared to PtON-TBBI (2.01 \u0026mu;s), owing to the slightly decreased \u003csup\u003e3\u003c/sup\u003eMLCT character of its T\u003csub\u003e1\u003c/sub\u003e state. The significantly decreased FWHM and \u003cem\u003eS\u003c/em\u003e\u003csub\u003eM\u003c/sub\u003e values, small\u0026nbsp;solvatochromic effect, and enhanced quantum efficiency of PtQS1\u0026nbsp;revealed an\u0026nbsp;increased \u003csup\u003e3\u003c/sup\u003eLE character of the T\u003csub\u003e1\u003c/sub\u003e state, an enhanced molecular rigidity, as well as suppressed molecular vibrations and nonradiative decays. These results indicate that the excited-state properties of Pt(II) complexes can be precisely controlled through\u0026nbsp;rational molecular design.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDevice performance\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe then investigated the\u0026nbsp;electroluminescence\u0026nbsp;(EL) properties of a PtQS1-based device\u0026nbsp;(Fig. 4). The HOMO and LUMO levels\u0026nbsp;of PtQS1\u0026nbsp;were calculated from its redox potentials, as measured by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) (Supplementary\u0026nbsp;Table 3, Supplementary Fig. 9).\u0026nbsp;We fabricated a bottom-emitting\u0026nbsp;device\u0026nbsp;with the following\u0026nbsp;structure:\u0026nbsp;ITO/HATCN (20 nm)/TAPC (60 nm)/SiCzCz (5 nm)/8 wt.% PtQS1:65 wt.% SiCzCz:27 wt.% SiTrzCz2 (35 nm)/mSiTrz (5 nm)/50 wt.% mSiTrz:50 wt.% Liq (31 nm)/LiF (1.5 nm)/Al, where ITO = indium tin oxide, HATCN = 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene, TAPC = 1,1\u0026apos;-bis[4-(di-\u003cem\u003ep\u003c/em\u003e-tolylamino)phenyl]cyclohexane, mSiTrz = 2-phenyl-4,6-bis(3-(triphenylsilyl)phenyl)-1,3,5-triazine, and Liq = lithium quinolin-8-olate.\u0026nbsp;The energy level diagram and chemical structures of the materials are illustrated in Fig. 4a.\u0026nbsp;SiCzCz and SiTrzCz2 were employed as \u003cem\u003ep\u003c/em\u003e-type and \u003cem\u003en\u003c/em\u003e-type host materials, respectively;\u003csup\u003e17\u0026nbsp;\u003c/sup\u003emoreover,\u0026nbsp;SiCzCz and mSiTrz were used as electron and hole blocking layers, respectively, because the high HOMO level of SiCzCz and the deep LUMO level of mSiTrz could confine the excitons inside the emitting layer; TAPC and mSiTrz:Liq served as hole and electron transport layers, whereas HATCN and LiF acted as hole and electron injection layers, respectively; finally, ITO and Al were used as anode and cathode, respectively.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe PtQS1-based device emitted deep-blue light and displayed an extremely narrow emission peak at 464 nm, with small FWHM and\u0026nbsp;\u003cem\u003eS\u003c/em\u003e\u003csub\u003eM\u003c/sub\u003e values of only 17.1 nm and 0.270, respectively, achieving CIE coordinates of (0.13, 0.11) (Fig. 4b). Particularly, no EL spectral broadening was observed, and the EL spectrum had the same FWHM as the PL spectrum in dichloromethane (Fig. 3c); moreover, the EL spectrum showed a further reduced \u003cem\u003eS\u003c/em\u003e\u003csub\u003eM\u003c/sub\u003e. Previous work found that a square-planar Pt(II) complex and SiTrzCz2 with a deep LUMO level could generate an exciplex, leading to reduced color purity;\u003csup\u003e17,24\u003c/sup\u003e however,\u0026nbsp;no\u0026nbsp;exciplex emission was observed for the PtQS1-based device, because the bulky\u0026nbsp;3D configuration of PtQS1 suppressed the intermolecular interactions.\u0026nbsp;The FWHM value of\u0026nbsp;17.1 nm was smaller than those of micro light-emitting diodes (microLEDs) and quantum-dot light-emitting diodes (QD-LEDs).\u003csup\u003e48\u0026ndash;50\u003c/sup\u003e The device exhibited a low turn-on voltage of 2.4 V, a running voltage of 5.4 V at a practical luminance of 1000 cd/m\u003csup\u003e2\u003c/sup\u003e, and a maximum luminescence (\u003cem\u003eL\u003c/em\u003e\u003csub\u003emax\u003c/sub\u003e) of 48968 cd/m\u003csup\u003e2\u0026nbsp;\u003c/sup\u003e(Fig. 4c). It also achieved a maximum EQE of 35.5%, and could still reach an EQE of 31.3% at a practical luminance of 1000 cd/m\u003csup\u003e2\u003c/sup\u003e; moreover, the EQE could be maintained at 27.0% and 23.6% at 5000 and 10000 cd/m\u003csup\u003e2\u003c/sup\u003e, respectively(Fig. 4d). Finally, the device also exhibited a maximum current efficiency (CE) of 30.7 cd/A, which still maintained at 27.1, 23.4, and 20.6 cd/A at 1000, 5000, and 10000 cd/m\u003csup\u003e2\u003c/sup\u003e, respectively(Fig. 4e). The high efficiency was attributed to the lower-lying T\u003csub\u003e1\u003c/sub\u003e state of PtQS1 (2.72 eV) compared to that of the SiCzCz:SiTrzCz2\u0026nbsp;exciplex host (2.84 eV)\u003csup\u003e17\u003c/sup\u003e, which enabled an efficient and complete energy transfer from the hosts to the dopant molecules. The low efficiency roll-off indicated reduced\u0026nbsp;triplet\u0026ndash;triplet and triplet\u0026ndash;polaron annihilations, owing to the\u0026nbsp;suppressed intermolecular interactions. The chemical structures of deep-blue emitters based on Pt(II) and Ir(III) complexes, and of\u0026nbsp;multiple resonance (MR)\u0026nbsp;deep-blue\u0026nbsp;emitters based on organic boron-nitrogen (BN) compounds are\u0026nbsp;shown\u0026nbsp;in Supplementary Figs.10, 11, and 12, respectively; moreover,\u0026nbsp;the device performances of their doped deep-blue phosphorescent OLEDs and MR-OLEDs with CIE\u003csub\u003ey\u003c/sub\u003e \u0026lt; 0.15 are summarized in Supplementary Tables 5\u0026ndash;7; additionally, the\u0026nbsp;device performances of\u0026nbsp;the closely-watched\u0026nbsp;deep-blue\u0026nbsp;hyperfluorescence (HF)-OLEDs\u0026nbsp;were summarized\u0026nbsp;in Supplementary Table 8. To the best of our knowledge, the present system is the first deep-blue phosphorescent OLEDs with CIE\u003csub\u003ey\u003c/sub\u003e \u0026lt; 0.15 to achieve an\u0026nbsp;FWHM value of \u0026lt; 20 nm\u0026nbsp;(Supplementary Tables 5 and 6). Moreover, the\u0026nbsp;PtQS1-based device achieved record-high EQEs at high luminance values of 1000, 5000, and 10000 cd/m\u003csup\u003e2\u003c/sup\u003e among reported deep-blue OLEDs with CIE\u003csub\u003ey\u0026nbsp;\u003c/sub\u003e\u0026lt; 0.15, including phosphorescent OLEDs based on Pt(II) and Ir(III) complexes, BN-based MR-OLEDs, and also one of the best among HF-OLEDs (Fig. 4f and\u0026nbsp;Supplementary Fig. 13).\u0026nbsp;The\u0026nbsp;\u003cem\u003eL\u003c/em\u003e\u003csub\u003emax\u003c/sub\u003e of the PtQS1-based device (48968 cd/m\u003csup\u003e2\u003c/sup\u003e)also represents one of the highest luminance values among\u0026nbsp;those reported for deep-blue OLEDs with CIE\u003csub\u003ey\u0026nbsp;\u003c/sub\u003e\u0026lt; 0.15\u0026nbsp;(Fig. 4g).\u003c/p\u003e\n\u003cp\u003eBased on the top-emitting architectures adopted by all commercial OLEDs, and also the narrow emission spectrum of the PtQS1-based device, we fabricated a top-emitting OLED using PtQS1 as emitter and compared it with a PtON-TBBI-based OLED; the corresponding device performances and materials are shown in\u0026nbsp;Fig. 5\u0026nbsp;and\u0026nbsp;Supplementary Fig. 14, respectively. The\u0026nbsp;PtQS1 device showed a deep-blue emission peaking at 464 nm, read shifted by 5 nm compared to the PtON-TBBI device; however, the PtQS1 device achieved a much narrower spectrum, with a FWHM value of 13.1 nm and CIE coordinates of (0.13, 0.06) at 1000 cd/m\u003csup\u003e2\u0026nbsp;\u003c/sup\u003e(Fig. 5a). These\u0026nbsp;chromaticity coordinates meet the pure blue standards of NTSC and EBU, and are extremely close to the BT.2020 standard (0.131, 0.046). Moreover, the\u0026nbsp;PtQS1 device also exhibited a low running voltage of 3.9 V at 1000 cd/m\u003csup\u003e2\u003c/sup\u003e, significantly lower than that of the PtON-TBBI device (4.3 V) (Fig. 5b). Importantly, the PtQS1 device showed a high maximum EQE of 49.5% at 147 cd/m\u003csup\u003e2\u003c/sup\u003e, which was 1.83 times that of the PtON-TBBI device; and still maintained EQEs of 46.4% and 39.5% at\u0026nbsp;pratical\u0026nbsp;luminance values of 1000 and 5000 cd/m\u003csup\u003e2\u003c/sup\u003e, respectively, which were 1.86 and 1.91 times higher than those of the PtON-TBBI device\u0026nbsp;(Fig. 5c). Notably, the PtQS1 device could still achieve an EQE of 34.3% at a high luminance of 10000 cd/m\u003csup\u003e2\u0026nbsp;\u003c/sup\u003e(Fig. 5c). This result indicated that the small FWHM of the emission spectrum could significantly enhance the efficiency of the top-emitting OLED. To our knowledge, the present PtQS1 device is the first deep-blue OLED with CIE\u003csub\u003ey\u003c/sub\u003e \u0026lt; 0.1 and EQE \u0026gt; 30% at 10000 cd/m\u003csup\u003e2\u003c/sup\u003e. The blue index (BI) is a key parameter used to evaluate the performance of blue OLEDs in the industry, defined as the ratio of current efficiency to CIE\u003csub\u003ey\u003c/sub\u003e.\u003csup\u003e16,18\u003c/sup\u003e The PtQS1 device achieved a maximum BI value of up to 468 cd A\u003csup\u003e\u0026ndash;1\u003c/sup\u003eCIE\u003csub\u003ey\u003c/sub\u003e\u003csup\u003e\u0026ndash;1\u003c/sup\u003e with a small efficiency roll-off, and retained 438, 372, and 325 cd A\u003csup\u003e\u0026ndash;1\u003c/sup\u003eCIE\u003csub\u003ey\u003c/sub\u003e\u003csup\u003e\u0026ndash;1\u003c/sup\u003e at 1000, 5000, and 10000 cd/m\u003csup\u003e2\u003c/sup\u003e, respectively, representing significantly enhanced BI values compared to the PtON-TBBI device\u0026nbsp;(Fig. 5d).\u0026nbsp;The\u0026nbsp;BI value of the PtQS1-based device is about twofold that of commercial deep-blue fluorescent OLEDs.\u0026nbsp;We also investigated the light color stability and operational lifetime of the PtQS1 device. The emission peaks and FWHMs of the device remained basically unchanged within a wide range of practical brightness values, suggesting a high light color stability (Fig. 5e). Importantly, the PtQS1 device showed a long half-lifetime (defined as the time at which the luminance decays to 50% of the initial luminance) of 670 h at a \u003cem\u003eL\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e of 1000 cd/m\u003csup\u003e2\u003c/sup\u003e, which was comparable to or even superior to that of the PtON-TBBI device\u0026nbsp;(Fig. 5f). The highly efficient and stable\u0026nbsp;PtQS1 device,\u0026nbsp;with low running voltage and high color purity exhibits an excellent voerall performance reported to date for deep-blue OLEDs with CIE\u003csub\u003ey\u003c/sub\u003e \u0026lt; 0.10. These results suggest that a phosphorescent OLED with one Pt(II) emitter and two exciplex hosts could realize a high device performance for potentially practical applications, which could overcome the problems of four-source co-evaporation and the accurate control of the doping concentration of the light-emitting layer in the manufacturing process of OLED displays.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe challenges associated with blue OLEDs severely hinder the development of the OLED field. The device efficiency, operational lifetime, color purity, brightness, and running voltage are all important parameters affecting commercial applications; however, simultaneously satisfying all the corresponding requirements represents a major challenge, and advanced emitters are critical to overcome the issue.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn this study, we developed a novel strategy to design robust phosphorescent Pt(II) emitters. By incorporating an\u0026nbsp;extended \u0026pi;-conjugation BFCz moiety to increase the proportion of \u003csup\u003e3\u003c/sup\u003eLE character in the T\u003csub\u003e1\u003c/sub\u003e state, and assembling a bulky PTBTP group to obtain a rigid 3D geometry to suppress intermolecular interactions,\u0026nbsp;PtQS1 exhibited an extremely narrow emission spectrum (with an FWHM of 17.1 nm and a small \u003cem\u003eS\u003c/em\u003e\u003csub\u003eM\u003c/sub\u003e of 0.295), along with a high quantum efficiency of 99%.\u0026nbsp;We also developed a facile and efficient synthetic route, that enabled the large-scale production of PtQS1 and facilitated the investigation of device performance.\u003c/p\u003e\n\u003cp\u003eThe lower-lying T\u003csub\u003e1\u003c/sub\u003e state of PtQS1 (2.72 eV) compared to that of the SiCzCz:SiTrzCz2\u0026nbsp;exciplex host (2.84 eV) enabled efficient energy transfer from the host to the dopant molecules.\u0026nbsp;A PtQS1-based bottom-emitting deep-blue OLED achieved a low turn-on voltage (\u003cem\u003eV\u003c/em\u003e\u003csub\u003eon\u003c/sub\u003e = 2.4 V), a high color purity (FWHM = 17.1 nm, \u003cem\u003eS\u003c/em\u003e\u003csub\u003eM\u003c/sub\u003e = 0.270, CIE\u003csub\u003ey\u003c/sub\u003e = 0.11) and a high maximum brightness (\u003cem\u003eL\u003c/em\u003e\u003csub\u003emax\u003c/sub\u003e = 48968 cd/m\u003csup\u003e2\u003c/sup\u003e); in addition, it exhibited high EQEs of 31.3%, 27.0%, and 23.6% at 1000, 5000, and 10000 cd/m\u003csup\u003e2\u003c/sup\u003e, respectively. This system is the first phosphorescent OLED with CIE\u003csub\u003ey\u003c/sub\u003e \u0026lt; 0.15 to achieve a\u0026nbsp;FWHM of less than 20 nm. Because of its narrow EL spectrum, a\u0026nbsp;PtQS1-based top-emitting OLED demonstrated further enhanced device performances through microcavity effects. The PtQS1-based OLED achieved an enhanced color purity (FWHM = 13.1 nm, CIE\u003csub\u003ey\u003c/sub\u003e = 0.06), a reduced running voltage (\u003cem\u003eV\u003c/em\u003e = 3.9 V at 1000 cd/m\u003csup\u003e2\u003c/sup\u003e), along with a maximum EQE of 49.5%; additionally, it still maintained EQEs of 46.4%, 39.5%, and 34.3% at 1000, 5000, and 10000 cd/m\u003csup\u003e2\u003c/sup\u003e, respectively. The deep-blue OLED also exhibited a maximum BI of up to\u0026nbsp;468 cd A\u003csup\u003e\u0026ndash;\u003c/sup\u003e\u003csup\u003e1\u003c/sup\u003eCIE\u003csub\u003ey\u003c/sub\u003e\u003csup\u003e\u0026ndash;\u003c/sup\u003e\u003csup\u003e1\u003c/sup\u003e and\u0026nbsp;a long half-lifetime of 670 h at a \u003cem\u003eL\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e of 1000 cd/m\u003csup\u003e2\u003c/sup\u003e. This work presents a valuable molecular design strategy of robust Pt(II) emitters for developing high-performance deep-blue OLEDs. We envisage that our study may promote the development of deep-blue phosphorescent OLEDs suitable for real-world applications in displays and lighting.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData Availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that the main data supporting the findings of this study are available within the article and its Supplementary Information files. Extra data are available from the corresponding author upon request. Crystallographic data for the structure reported in this Article have been deposited at the Cambridge Crystallographic Data Centre, under deposition numbers CCDC 2346824 (PtQS1). Copies of the data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/. Source data are provided with this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the National Natural Science Foundation of China (Grant No. 22178319 and\u0026nbsp;22138011), the Zhejiang Province Vanguard Goose-Leading Initiative (2024C01260). We thank Jiyong Liu from Zhejiang University for the help in the single crystal measurement and analysis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eG.L. and Y.S initiated and supervised the project. G.L. designed the material and analysed the data. Q.C. and H.Y. synthesized and characterized the Pt(II) emitters, host materials and performed the computational calculation. K.W. fabricated the devices. G.L. contributed to the manuscript writing. All authors discussed the progress of the research and reviewed the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing financial interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eForrest,\u0026nbsp;S. R. The path to ubiquitous and low-cost organic\u0026nbsp;electronic appliances on plastic. \u003cem\u003eNature\u003c/em\u003e. \u003cstrong\u003e428\u003c/strong\u003e, 911\u0026ndash;918 (2004).\u003c/li\u003e\n \u003cli\u003eHa, J. M., Hur, S. H., Pathak, A., Jeong, J.-E. \u0026amp; Woo,\u0026nbsp;H. Y. 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Highly efficient and stable InP/ZnSe/ZnS quantum dot light-emitting diodes. \u003cem\u003eNature.\u003c/em\u003e \u003cstrong\u003e575\u003c/strong\u003e, 634\u0026ndash;638 (2019).\u003c/li\u003e\n \u003cli\u003eZhang, W.,\u0026nbsp;Li, B.,\u0026nbsp;Chang, C.,\u0026nbsp;Chen, F.,\u0026nbsp;Zhang, Q.,\u0026nbsp;Lin, Q.,\u0026nbsp;Wang, L.,\u0026nbsp;Yan, J.,\u0026nbsp;Wang, F.,\u0026nbsp;Chong, Y.,\u0026nbsp;Du, Z., Fan, F.\u0026nbsp;\u0026amp;\u0026nbsp;Shen,\u0026nbsp;H. Stable and efficient pure blue quantum-dot LEDs enabled by inserting an anti-oxidation layer. \u003cem\u003eNat. Commun.\u003c/em\u003e \u003cstrong\u003e15\u003c/strong\u003e, 783 (2024).\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cstrong\u003eQuantum Chemical Calculations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe theoretical calculations were performed using\u0026nbsp;Gaussian 16 package. Themolecular geometries of S\u003csub\u003e0\u003c/sub\u003e were\u0026nbsp;optimized with the DFT method at the MN15 level. The DFT calculations were performed using a B3LYP function with a basis set of 6-31G(d) for C, H, O and N atoms; the LANL2DZ basis set with ECP was used for Pt atoms.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eX-ray Crystallography\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eX-ray diffraction data were collected at 170 K on a Bruker D8 Venture diffractometer using graphite-monochromated Mo-K\u0026alpha; radiation (\u003cem\u003e\u0026lambda;\u0026nbsp;\u003c/em\u003e= 0.71073 \u0026Aring;) from a rotating anode generator.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePhotophysical Measurements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe absorption spectra were measured on a Hitachi U-3900 UV\u0026minus;VS Spectrometer.\u0026nbsp;Steady state emission experiments were performed on HITACHI F-7000 spectrometer.\u0026nbsp;Low temperature (77 K) emission spectra and\u0026nbsp;lifetimes\u0026nbsp;were measured in 2-MeTHF cooled with liquid nitrogen.\u0026nbsp;Lifetime measurements and quantum efficiency were measured using an Edinburgh FS5 spectrofluorometer equipped with an integrating sphere.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eOLED Fabrication and Characterization\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eBottom-emitting\u0026nbsp;devices were fabricated by vacuum thermal evaporation, and were tested outside glove box after encapsulation. Prior to deposition, the prepatterned ITO coated glass substrates were cleaned by subsequent sonication in deionized water, acetone, and isopropanol.\u0026nbsp;The metal layer and organic layers were fabricated by vacuum thermal evaporation on the cleaned ITO glass substrate under vacuum (\u0026lt; 4 \u0026times; 10\u003csup\u003e\u0026ndash;4\u003c/sup\u003e Pa) with 4 \u0026Aring;/s deposition rate for aluminum cathode and 2 \u0026Aring;/s for organic layers. The device areas were 9 mm\u003csup\u003e2\u003c/sup\u003e (3 mm \u0026times; 3 mm). The current density-voltage-luminance characteristics of OLEDs were measured using a Keithey 2400 Source meter and a Keithey 2000 Source multimeter equipped with a calibrated silicon photodiode. The EL spectra were recorded with a multichannel spectrometer (PMA12, Hamamatsu Photonics). Top-emitting OLEDs were fabricated and tested in R\u0026amp;D Evaporation System (OASIS-C-E4T1-PcG-2020, Choshu Industry Co., Ltd.).\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-5009247/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5009247/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Organic light-emitting diodes (OLEDs) represent a revolutionary technology, that has been successfully commercialized in full-color displays. However, this technology is still severely limited by the low efficiency of blue OLEDs. Developing high-performance blue OLEDs is a major challenge, and emitters are critical for overcoming this issue. Herein, we developed a strategy to design phosphorescent Pt(II) complexes with a locally excited-dominated character and a rigid 3D geometry to suppress intermolecular interactions, enabling robust deep-blue emitters. A bottom-emitting OLED realized a high color purity with a full-width at half-maximum (FWHM) of 17.1 nm, a high maximum brightness of 48968 cd/m2, and high external quantum efficiencies (EQEs) of 31.3%, 27.0%, and 23.6% at 1000, 5000, and 10000 cd/m2, respectively. A top-emitting OLED achieved an enhanced color purity (FWHM = 13.1 nm, CIEy = 0.06), a low running voltage (3.9 V at 1000 cd/m2), and a maximum EQE of 49.5%, and maintained EQEs of 46.4%, 39.5%, and 34.3% at 1000, 5000, and 10000 cd/m2, respectively. The OLED also exhibited a maximum blue index (BI) of 468 cd A-1CIEy-1 and a long half-lifetime of 670 h at an initial luminance of 1000 cd/m2. This study provides a important strategy to develop high-performance deep-blue phosphorescent OLEDs.","manuscriptTitle":"High-performance deep-blue phosphorescent organic light-emitting diodes enabled by a platinum(II) emitter","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-09-09 17:20:56","doi":"10.21203/rs.3.rs-5009247/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-photonics","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"nphoton","sideBox":"Learn more about [Nature Photonics](https://www.nature.com/nphoton/)","snPcode":"41566","submissionUrl":"https://mts-nphot.nature.com/cgi-bin/main.plex","title":"Nature Photonics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Research","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"1848d480-4800-44fc-b3ba-9781c00cf8f8","owner":[],"postedDate":"September 9th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":37212287,"name":"Physical sciences/Materials science/Materials for optics/Lasers, LEDs and light sources/Organic LEDs"},{"id":37212288,"name":"Physical sciences/Chemistry/Materials chemistry/Optical materials"}],"tags":[],"updatedAt":"2025-07-10T09:15:19+00:00","versionOfRecord":{"articleIdentity":"rs-5009247","link":"https://doi.org/10.1038/s41566-025-01706-0","journal":{"identity":"nature-photonics","isVorOnly":false,"title":"Nature Photonics"},"publishedOn":"2025-07-09 04:00:00","publishedOnDateReadable":"July 9th, 2025"},"versionCreatedAt":"2024-09-09 17:20:56","video":"","vorDoi":"10.1038/s41566-025-01706-0","vorDoiUrl":"https://doi.org/10.1038/s41566-025-01706-0","workflowStages":[]},"version":"v1","identity":"rs-5009247","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5009247","identity":"rs-5009247","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}