Interface-directed charge regulation enables efficient perovskite/organic hybrid tandem LEDs

Interface-directed charge regulation enables efficient perovskite/organic hybrid tandem LEDs | 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 Interface-directed charge regulation enables efficient perovskite/organic hybrid tandem LEDs Liang-Sheng Liao, Ye Wang, Dong-Ying Zhou, Aziz Khan, Sheng-Fu Wang, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8531730/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Near infrared (NIR) light-emitting devices hold significant promise for applications in night vision, telecommunications, and biomedical imaging. Hybrid tandem light-emitting diodes (LEDs) that combine quantum-dot (QD)-based and organic emissive subunits represent a compelling strategy to surpass an external quantum efficiency (EQE) of 30%. However, in series-connected architectures, the intrinsic mismatch in charge-transport properties and distinct efficiency roll-off characteristics between the two emissive units hinder ideal efficiency summation and limit overall device performance under identical current injection. Here, we report a high-performance hybrid NIR tandem LED in which this imbalance is mitigated by selectively enhancing carrier injection and transport in the performance-limiting QD-based emissive unit. Through molecular engineering of the electron-transporting layer and rational design of the charge-generation interface, the electrical characteristics of the QD unit is precisely tailored to match that of the high-efficiency organic NIR emitter. As a result, the hybrid tandem device achieves a near-ideal voltage addition and markedly improved electroluminescence, delivering a peak external quantum efficiency of 35% with stable emission at 780 nm. This work establishes a general design principle for overcoming current-driving imbalance in heterogeneous tandem architectures and paves the way toward high-performance NIR light sources. Physical sciences/Optics and photonics/Lasers, LEDs and light sources Physical sciences/Materials science/Materials for optics/Lasers, LEDs and light sources Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Tandem light-emitting diode (LEDs) architectures, in which multiple electroluminescent units are electrically connected in series, represent a promising route to simultaneously enhance efficiency, brightness, and operational stability beyond the intrinsic limits of single-emissive devices. 1 – 3 By distributing the operating voltage across multiple subunits, tandem designs can suppress current-induced degradation and reduce efficiency roll-off, making them attractive for high-brightness and high-resolution display applications. To date, tandem concepts have been extensively explored in organic light-emitting diodes (OLEDs) and quantum-dot light-emitting diodes (QLEDs), achieving impressive performance improvements. However, despite substantial progress in organic/organic and quantum-dot/quantum-dot tandem LEDs, conventional tandem approaches often face challenges such as broadband emission, complex multilayer solution processing, and strict solvent orthogonality requirements, which complicate device fabrication and limit material compatibility. 4 – 7 Hybrid tandem LEDs that integrate a solution-processed QLED subunit with a vacuum-deposited OLED subunit have recently emerged as a promising alternative to overcome these limitations. 8 – 12 By combining the narrow emission bandwidth and spectral tunability of colloidal quantum dots with the mature device architectures and charge-transport materials of OLEDs, hybrid tandem designs offer a feasible pathway toward high-performance emission without severe solvent-induced damage to underlying layers. In particular, hybrid near-infrared (NIR) tandem LEDs are appealing for applications such as optical communication, night-vision displays, and bioimaging, where high radiance and spectral purity are required. 13 – 18 Despite these advantages, the practical implementation of hybrid tandem LEDs remains challenging, and their performance has not yet reached the theoretical expectations of ideal voltage and efficiency additivity. The development of hybrid tandem LEDs is fundamentally limited by the intrinsic electroluminescent mismatch between QLED and OLED subunits. Owing to their fundamentally different emission mechanisms, charge-transport mechanisms, recombination dynamics, and efficiency roll-off behaviors, QLEDs and OLEDs typically exhibit distinct current density–voltage–radiance characteristics. 19 – 24 When such subunits are electrically connected in series, this mismatch leads to severe current-driving imbalance, where one subunit operates away from its optimal efficiency regime while the other dominates the current flow. As a consequence, hybrid tandem devices often suffer from non-additive electroluminescent performance, emission imbalance, and compromised operational stability, particularly under high current densities required for practical applications. Addressing this intrinsic current-driving imbalance is therefore essential for realizing efficient and stable hybrid tandem LEDs. In this work, we address this challenge by selectively enhancing carrier injection and transport in the weaker NIR QLED subunit to achieve balanced current driving with an efficient NIR OLED subunit. Through targeted molecular engineering of the electron-transporting layer and rational design of the charge-generation interface, the electrical characteristics of the QLED are systematically tuned to better match those of the OLED. This strategy enables efficient series integration of the two emissive units, leading to near-ideal voltage addition and substantially improved electroluminescent performance in hybrid NIR tandem LEDs with EQE of 35% at 780 nm. Our results establish a general design principle for overcoming current-driving imbalance in hybrid tandem architectures and provide a viable route toward high-efficiency, spectrally pure NIR light sources. Results and discussion FAPbI 3 -based perovskite nanocrystals and a Pt(II) complex emitter (Dph-3-f) were employed as representative near-infrared emissive materials for the QLED and OLED subunits, respectively. These two emissive systems exhibit comparable NIR emission wavelengths centered at approximately 780 nm and are based on well-established device architectures, enabling a meaningful comparison in hybrid tandem integration (Fig. 1 a). Despite their spectral similarity, the QLED and OLED display markedly different current density–efficiency characteristics, leading to emitting imbalance. As shown in Figure S1 , the NIR QLED reaches its peak external quantum efficiency (EQE) of 19.5% at a low current density of ~ 0.05 mA cm – 2 and undergo a serious efficiency roll of (EQE of 8.2% at 10 mA cm – 2 and EQE of 5.6% at 50 mA cm – 2 ), while the NIR OLED achieves its peak EQE of 14.6% at a higher current density (~ 0.1 mA cm – 2 ) and undergo a milder efficiency roll off (EQE of 11.2% at 10 mA cm – 2 and EQE of 7.5% at 50 mA cm – 2 ). The fast efficiency drop of the QLED unit making the QLED a dominant to a weaker subunit, leading to spectral shift, incomplete stacking of emission and severe efficiency roll-off in the tandem LEDs. The electroluminescent of tandem demonstrated that simply combining the two units together only reach a peak EQE of 28%, far below the summed performance of the individual subunits. Thus, mitigating the efficiency roll-off of the weaker subunit is essential for improving current-driving balance between the subunits and enhancing the overall tandem efficiency. We attribute the pronounced efficiency roll-off observed in the NIR QLED unit primarily to the limited electron injection and transport characteristics of the electron-transporting layer (ETL). 25 – 30 While the multiple phosphine oxide groups in 2,4,6-tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine (POT2T) based ETL are effective in passivating surface defects of perovskite nanocrystals and provide a suitable lowest unoccupied molecular orbital (LUMO) energy level for charge injection, its three-dimensional molecular configuration introduces significant steric hindrance, which disrupts continuous π-conjugation between neighboring molecules and weakens intermolecular electronic coupling. 31 , 32 Besides, due to its amorphous nature, POT2T forms a disordered ETL/QDs interface with poor molecular packing, which further reduces electron mobility (Fig. 1 a). Especially under high current density, the limited electron transport results in the serious imbalance between electron and hole injection, leading to inefficient recombination and hole leakage at the ETL/QD interface (Fig. 1 b). To overcome these limitations, we designed a linearly structured ETL (ANPO) with a rigid backbone and extended π-conjugation (Fig. 1 a). Compared with the bulky 3D configuration of POT2T, the linear and planar geometry of ANPO enables extended π-conjugation along the molecular axis, promoting stronger π-π stacking between adjacent molecules. 33 This ordered stacking forms continuous electronic pathways, greatly enhancing electron delocalization and intermolecular orbital overlap, which in turn increases electron mobility. The symmetrical phosphine oxide anchoring groups not only stabilize the LUMO energy level but also strengthen the interaction with QDs, ensuring a uniform and well-aligned ETL/QD interface. This optimized packing suppresses interfacial disorder, reduces trap-assisted recombination, and facilitates rapid electron injection into the QDs. As a result, ANPO can effectively balance electron and hole currents, minimize interfacial charge accumulation, and significantly reduce efficiency roll-off in QLED-based tandem devices (Fig. 1 c). To verify the improved π-π stacking of ANPO, we first investigated the two-dimensional grazing-incidence wide-angle X-ray scattering (GIWAXS) of the two ETL films (Fig. 1 d). The POT2T film exhibited featureless, diffuse scattering halos, indicating a predominantly amorphous structure with no long-range molecular order. In contrast, the ANPO film displayed distinct diffraction rings, particularly along the out-of-plane direction at q ≈ 1.7 Å – 1 , corresponding to a d-spacing of approximately 3.7 Å. 34–36 This diffraction feature is characteristic of π-π stacking interactions between adjacent conjugated backbones. Besides, the ANPO film exhibits longer crystal coherence length ( L c ), which is 24.1 Å compared to 21.6 Å of the POT2T film (Fig. 1 e). This indicates that ANPO forms more extended crystalline domains with higher structural coherence along the stacking direction, reflecting better molecular packing continuity and fewer lattice defects. AFM and SEM analyses further reveal that ANPO forms a more uniform film morphology, exhibiting a smaller surface roughness of 2.61 nm compared with 3.27 nm for POT2T ( Figure S2,3 ). We then performed the spectroscopic characterizations of the two ETLs. Both absorption and PL spectra of the ANPO film are redshifted compared with those of the POT2T film (Fig. 1 f). The optical bandgap of the ANPO film is 3.0 eV, which is smaller than POT2T (3.97 eV). Combined with UPS spectra ( Figure S4 ), the LUMO onset energy is − 3 eV for ANPO, which is ~ 0.4 eV lower than the POT2T, facilitating the electron injection ( Figure S5 ). To gain deeper insights into the ETL/QD interface and carrier injection, we performed density functional theory (DFT) calculations to examine the interaction between ETLs and the QDs. The total electron density difference maps clearly visualize how the ETLs interact with the QDs (Fig. 2 a,b). For ANPO, its symmetrical phosphine oxide anchoring groups strengthen binding to the QDs and drive the formation of an ordered planar geometry, which facilitates efficient interfacial charge transfer. We also investigated the surface electrostatic potential (ESP) of two molecules ( Figure S7 ). POT2T typically has low ESP (green) near the edges and negative (red) regions are typically hindered by the nearby phenyls, making it a worse candidate for perovskite attachment. 37 On the contrary, the linear structure and the presence of oxygen atoms in ANPO creates regions of negative potential, enabling its effective attachment to Pb atoms of the perovskite. We then analyzed the charge displacement profiles along the z-axis and found that ANPO creates a larger disparity in electron cloud distribution, generating a stronger internal electric field that accelerates electron transfer and injection. 32 , 38 In contrast, the POT2T/QD interface exhibits localized charge transfer, and the multiple phosphine oxide groups induce a distorted, nonplanar adsorption geometry that hinders electron transport. We then investigated charge recombination dynamics using time-resolved electroluminescence (TREL) and photoluminescence (TRPL) test for different ETLs. The faster rise-time of the ANPO in TREL spectrum demonstrates the better carrier injection and recombination (Fig. 2 d). 39 , 40 We also employed TRPL to probe the carrier recombination dynamics of QD films deposited on different ETL layers. The PL decay of the QDs on ANPO exhibits a noticeably shorter average lifetime compared with that on POT2T (Fig. 2 e). This faster decay indicates more efficient electron extraction from the QDs to the ETL, suggesting that ANPO provides a better interfacial charge-transfer pathway. We further measured electron mobilities via space-charge-limited current (SCLC) in electron-only devices ( Figure S8 ) (ITO/LiF (1 nm)/ETL (100 nm)/LiF (1 nm)/Al (100 nm)) (Fig. 2 f). ANPO-based devices exhibits a much higher current density than the POT2T and a faster electron mobilities of 1.0 × 10 –3 cm 2 V – 1 s – 1 compared to 4.8 × 10 –5 cm 2 V – 1 s – 1 for POT2T under an electric field of 6.4 × 10 5 V cm – 1 , which is comparable to hole mobility of PEDOT:PSS (5.76 × 10 –4 cm 2 V – 1 s – 1 ). 41 Finally, we performed the Kelvin probe force microscopy (KPFM), and found the ANPO delivers a larger work function compared to POT2T (Fig. 2 g,h) and a narrower CPD distribution (Fig. 2 i), indicating a stronger and more homogeneous surface charge transfer. To test the interaction between different ETLs and QDs, we then performed Fourier transform infrared (FTIR) ( Figure S9 ). The emergence of C-P symmetric (1410 cm – 1 ) demonstrated the attachment of both the ETLs on QDs surface. 37 Besides, Pb 2+ coordination passivation via P = O bonds was evidenced by pronounced shifts to lower binding energy of Pb 4 f through XPS spectrum ( Figure S10 ). Furthermore, the trap filled limit voltage (V TFL ) were tested through electron-only devices ( Figure S11 ). The V TFL for ANPO is 0.74 V, which is much lower than that of the POT2T (1.07 V). It was attributed to the better surface defects passivation of ANPO. This is consistent to trap density of states (tDOS) ( Figure S12 ), which prove the better defect passivation of the ANPO, and drive-level capacitance profiling (DLCP) test, demonstrating better trap passivation on the QDs/ETL surface. To demonstrate the QLED with ANPO whether reach a better current-driving balance with the OLED, we fabricated NIR QLEDs with the structure ITO/PEDOT:PSS/Poly-TPD/QDs/ANPO or POT2T/Liq/Al (Fig. 3 a,b). The QLEDs emitting efficient NIR light at 780 nm with no distinct EL shift under bias from 1.6 to 6 V (Fig. 3 c). The current density-voltage-radiance (J-V-R) curves (Fig. 3 d) show that ANPO-based devices exhibit a markedly higher current density than POT2T-based QLEDs, indicating enhanced charge injection. ANPO also boosts radiance performance by nearly threefold, delivering a maximum radiance of 35 W sr – 1 m – 2 compared to 12 W sr – 1 m – 2 for POT2T. The optimized ANPO-based QLED achieves a peak EQE of 21% at 1 mA cm – 2 , while sustains 9.8% EQE at 100 mA cm – 2 (4.1% of control sample), further confirming its efficiency advantage (Fig. 3 e). Besides, the Capacitance-voltage measurements show that the ANPO-based LED exhibits a lower overall capacitance and a much smaller, narrower peak than the control device (Fig. 3 f). This indicates reduced interfacial charge storage and trap filling, consistent with more efficient electron extraction and faster transport through the ANPO ETL. The superior performance of ANPO originates from its optimized molecular geometry, as revealed by DFT calculations. The linear backbone and symmetrical phosphine oxide anchoring groups promote ordered planar adsorption on the QD surface, yielding a uniform charge-transfer distribution across the ETL/QD interface. With the great improve in efficiency foll-off, we compared the EL behavior between two QLEDs and the OLED unit (Fig. 3 d). The curve of J-EQE of the QLED with ANPO perfectly contain the OLED curve, demonstrating better current-driving balance between the two subunits. We further evaluated operational stability by monitoring luminance decay at 1 mA cm – 2 (Fig. 3 f). The T 50 values are 82 min for POT2T-based QLEDs and 282 min for ANPO-based QLEDs, representing a 3.5-fold lifetime improvement. Collectively, these results indicate that the modified QLED is now fully compatible for tandem integration with the OLED. Finally, we integrated the improved ANPO-based QLEDs into a hybrid tandem LED, in which the QLED and OLED units were vertically stacked and connected through Bphen:LiNH 2 and mCP:MoO 3 , which serve as the charge generation layer. The energy band diagram of the hybrid device was constructed using energy level values from reported literature. The top OLED, with the structure ITO/HAT-CN/MoO 3 :CBP/CBP/Dph-3-f/CNT2T/LiF/Al, also emitted NIR light with a peak at 786 nm, closely matching the QLED emission (Fig. 4 a,b). Thanks to the suppression of efficiency roll-off and improved carrier balance in the optimized QLED sub-unit, the tandem device fully exploits the combined efficiencies of both emissive units. The current density-voltage (J-V) and radiance-voltage (R-V) curves reveal slower current injection for the hybrid device with POT2T due to the larger series resistance from multiple stacked layers (Fig. 4 c). Nevertheless, the hybrid tandem with ANPO reaches a radiance of 82 W sr – 1 m – 2 , demonstrating 1.7-fold improvement of that with POT2T. Most notably, it achieves a peak EQE of 35% (Fig. 4 d), nearly the sum of the individual QLED (21%) and OLED (14.6%) EQEs ( Figure S13 ), confirming highly efficient carrier generation, injection, and recombination in the tandem LEDs with ANPO. While the tandem with POT2T only exhibits EQE of 28%, greatly lowing than the sum of control QLED (19.5%) and OLED (14.6%), demonstrating the current driving imbalance. Besides, from the EL spectrum, we can find that the EL peak of the tandem with POT2T shifts greatly with the increase of the external bias, demonstrating the dominant subunit of the tandem shift from the QLED to the OLED ( Figure S14.a ). While the tandem with ANPO exhibits consistent emission, demonstrating the balance between the QLED and the OLED in the optimized tandem device ( Figure S14.b ). This value represents one of the record EQE for NIR LEDs (Fig. 4 e). Hybird tandem LEDs is no doubt a proming solution to the limitaion of efficient NIR LEDs. From the materials aspects, it greatly broaden the materials selection for the tandem LEDs, providing thousands of possible combinations among different types of materials. From the device fabrication aspect, it does not need complex fabrication technique and worry about solvent miscibility issue, and can be integrated into well-established manufacturing process of OLEDs. Due to the intrinsic difference of the two types of emissive materials, we demonstrated modulation the current-driving balance of the two types is very important in improving hybrid tandem LEDs efficiency. Furthermore, we expected additional improvement will be realized through the optical simulation and cavity-length optimization to reduce optical absorption and scattering, especially in a multilayer device structure that contain organic and inorganic materials. We expect hybrid tandem device to open a new avenue for bridging different types of emissive materials and to leverage their respective advantages for efficient electroluminancet performance. Conclusion We demonstrate that molecular-level ETL engineering enables NIR QLEDs to operate as viable tandem sub-units. By designing ANPO with a linear rigid backbone and symmetrical P = O anchoring groups, we achieve a more ordered QD/ETL interface, promote π-π stacking, and markedly enhance electron delocalization. These advances translate directly to devices: ANPO-based NIR QLEDs deliver EQEₘₐₓ of 21.2% and radiance of 35 W sr – 1 m – 2 , while sustaining 9.8% EQE at 100 mA cm – 2 (4.1% of control sample) and exhibiting a 3.5-fold lifetime extension. Furthermore, the improved QLED sub-unit spectrally and electrically matches a NIR OLED (Dph-3-f), enabling a hybrid tandem LED with a record EQE of 35%. Our results show that interface-ordering ETLs overcome the practical limitations of scarce, high-performance NIR emitters and unlock tandem architectures capable of achieving true performance additivity. Declarations Acknowledgement This work was supported by the National Natural Science Foundation of China (NSFC) (U25A20523, 62175171, 62375193, 62474119, and 62522514), Gusu Innovation and Entrepreneurship Leading Talent Program (ZXL2024367), National Key Research and Development Program of China (2024YFA1209500), Collaborative Innovation Center of Suzhou Nano Science & Technology (NANO-CIC), Suzhou Key Laboratory of Functional Nano & Soft Materials, the 111 Project, Joint International Research Laboratory of Carbon-Based Functional Materials and Devices. References Chen A et al (2020) Highly efficient tandem blue phosphorescent organic LEDs with external quantum efficiency exceeding 42%. Appl Phys Express 13:031002. 10.35848/1882-0786/ab6ed6 Liao LS, Slusarek WK, Hatwar TK, Ricks ML, Comfort DL (2008) Tandem Organic Light-Emitting Diode using Hexaazatriphenylene Hexacarbonitrile in the Intermediate Connector. 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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-8531730","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":580198148,"identity":"54e754a7-3c5c-4ac9-afc8-fb28f56c2aac","order_by":0,"name":"Liang-Sheng Liao","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAz0lEQVRIiWNgGAWjYBACPgbmhgMMDDZAZgIQsxGhhY2BEaQljUQtQOowKVr4DzYe+FFx3t7gePIDhg9lhxn4ZzcQ0CKR2HCw58ztxA1nnhkwzjh3mEHizgFCWoB+4W27nWBwI8GAmbftMIOBRAJBhzUc/Nt2zt7gRvoH5r9EaWFIbDjM23aAccONHANmRqK0AP1yWOZMcuLMM28KDvacS+eRuEFACz//4cMf31TY2fMdT9/44EeZtRz/DAJaUMABIOYhQf0oGAWjYBSMAlwAAOWSR1sDCBsMAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0002-2352-9666","institution":"Soochow University","correspondingAuthor":true,"prefix":"","firstName":"Liang-Sheng","middleName":"","lastName":"Liao","suffix":""},{"id":580198149,"identity":"48839c01-3a2b-4925-9695-7f1ab58f5fbf","order_by":1,"name":"Ye Wang","email":"","orcid":"","institution":"Soochow University","correspondingAuthor":false,"prefix":"","firstName":"Ye","middleName":"","lastName":"Wang","suffix":""},{"id":580198150,"identity":"4c7e9a36-cda4-40ac-993c-d5a23a8ea2b0","order_by":2,"name":"Dong-Ying Zhou","email":"","orcid":"https://orcid.org/0000-0002-2645-6212","institution":"Soochow University","correspondingAuthor":false,"prefix":"","firstName":"Dong-Ying","middleName":"","lastName":"Zhou","suffix":""},{"id":580198151,"identity":"d661a231-99eb-42dd-bf54-5a2d91003087","order_by":3,"name":"Aziz Khan","email":"","orcid":"","institution":"Soochow University","correspondingAuthor":false,"prefix":"","firstName":"Aziz","middleName":"","lastName":"Khan","suffix":""},{"id":580198152,"identity":"e8753d5b-54e0-4345-ae21-c3d1d51dbcd7","order_by":4,"name":"Sheng-Fu Wang","email":"","orcid":"","institution":"National Taiwan University","correspondingAuthor":false,"prefix":"","firstName":"Sheng-Fu","middleName":"","lastName":"Wang","suffix":""},{"id":580198153,"identity":"34499e52-b6a5-4be6-8e6f-37dfe7aaf2d5","order_by":5,"name":"Wei-Zhi Liu","email":"","orcid":"","institution":"Soochow University","correspondingAuthor":false,"prefix":"","firstName":"Wei-Zhi","middleName":"","lastName":"Liu","suffix":""},{"id":580198154,"identity":"2845ff51-29e9-4ad2-be68-5ff2a033a949","order_by":6,"name":"Wan-Shan Shen","email":"","orcid":"https://orcid.org/0009-0002-3602-7128","institution":"Soochow University","correspondingAuthor":false,"prefix":"","firstName":"Wan-Shan","middleName":"","lastName":"Shen","suffix":""},{"id":580198155,"identity":"4668916f-d9f1-4264-9c23-4c72a334d196","order_by":7,"name":"Zuoquan Jiang","email":"","orcid":"https://orcid.org/0000-0003-4447-2408","institution":"Soochow University","correspondingAuthor":false,"prefix":"","firstName":"Zuoquan","middleName":"","lastName":"Jiang","suffix":""},{"id":580198156,"identity":"acf76a28-a9bd-4939-94c4-5e41634ef67b","order_by":8,"name":"Yun Chi","email":"","orcid":"https://orcid.org/0000-0002-8441-3974","institution":"City University of Hong Kong","correspondingAuthor":false,"prefix":"","firstName":"Yun","middleName":"","lastName":"Chi","suffix":""},{"id":580198157,"identity":"babfc825-fb7e-403f-bb31-eb8bfdb2a179","order_by":9,"name":"Pi-Tai Chou","email":"","orcid":"https://orcid.org/0000-0002-8925-7747","institution":"National Taiwan University","correspondingAuthor":false,"prefix":"","firstName":"Pi-Tai","middleName":"","lastName":"Chou","suffix":""},{"id":580198158,"identity":"a76cdb76-422e-4100-af89-565c480f176f","order_by":10,"name":"Ya-Kun Wang","email":"","orcid":"https://orcid.org/0000-0002-8970-6856","institution":"Soochow University","correspondingAuthor":false,"prefix":"","firstName":"Ya-Kun","middleName":"","lastName":"Wang","suffix":""}],"badges":[],"createdAt":"2026-01-06 13:10:52","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8531730/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8531730/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":101268495,"identity":"b8563471-815c-4f3f-82b1-72a77eadba94","added_by":"auto","created_at":"2026-01-28 01:22:08","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":605664,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of charge recombination in tandem LEDs and optic spectrum of two ELTs. a, Schematic diagram of tandem device with different electron transport layer (ETL). Schematic diagram of QDs layer and b, POT2T.and c, ANPO. d, GIWAXS patterns of the POT2T (top) and ANPO (bottom) films. e, In-plane (along \u003cem\u003eq\u003c/em\u003e\u003csub\u003exy\u003c/sub\u003e) and out-of-plane (along \u003cem\u003eq\u003c/em\u003e\u003csub\u003ez\u003c/sub\u003e) from the GIWAXS patterns. f, PL spectra and g, absorption of the ETL films.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-8531730/v1/1d740c93de8c0e96be7d7419.png"},{"id":101297565,"identity":"5964ff41-5e29-42b7-8156-847c66d41af6","added_by":"auto","created_at":"2026-01-28 09:27:57","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":508487,"visible":true,"origin":"","legend":"\u003cp\u003eCharacteristics of carrier dynamic based on different ETLs. Schematic diagram of total electron density difference maps for a, POT2T and b, ANPO on QDs layer. c, Charge displacement profiles of POT2T/ and ANPO/QDs adsorption structures. d, TREL spectrum of the LEDs with ETL of POT2T and ANPO. e, TRPL spectrum of glass/QDs, glass/QDs/POT2T and glass/QDs/ANPO. f, Electric field-dependent electron mobility of POT2T and ANPO films. KPFM images of the film of g, POT2T and h, ANPO. i, Extracted potential distribution of the POT2T and ANPO films along a 5-μm line scan.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-8531730/v1/16e33553f9e5bb310fd70541.png"},{"id":101268492,"identity":"10810891-3653-4cd1-9a72-01fe08b523fe","added_by":"auto","created_at":"2026-01-28 01:22:08","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":276782,"visible":true,"origin":"","legend":"\u003cp\u003eEL characteristics of NIR QLEDs. a, Device structure of the QLEDs. b, Energy level of each layer of the QLED. c, EL spectrum of device with ANPO under different voltage. d, J-V and J-R curves of device with POT2T and ANPO. e, J-EQE curves of device with POT2T and ANPO. f, Capacitance-voltage (C-V) spectra biased at 4.5 V of devices with POT2T and ANPO. g, J-EQE curves of device with POT2T and ANPO compared to organic device. h, Lifetime test of the devices with POT2T and ANPO.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-8531730/v1/00ddab586ed620b77502458b.png"},{"id":101268494,"identity":"3e749d1b-1637-4dea-9a19-cabc6a29d3f2","added_by":"auto","created_at":"2026-01-28 01:22:08","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":340409,"visible":true,"origin":"","legend":"\u003cp\u003eEL characteristics of tandem NIR QLEDs. a, Schematic diagram of energy level of the tandem device structure. b, EL spectrum of the QDs unit, organic unit and tandem LED. c, J-V and J-R curves of tandem device with POT2T and ANPO. d, J-EQE curves of tandem device with POT2T and ANPO compared to organic device. EL spectrum of tandem LEDs with. e, Record EQE of NIR LEDs in recent years.\u003csup\u003e14,16,42-51\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-8531730/v1/1befa5d5ee6e6462b3585b9f.png"},{"id":101397747,"identity":"78e4f0c1-f8d4-4384-8c9c-fabf3de45258","added_by":"auto","created_at":"2026-01-29 09:36:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1951670,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8531730/v1/7bfcbc06-c794-4887-9cd6-d08a37bef361.pdf"},{"id":101268496,"identity":"50f8c278-416a-48ee-94d6-9b02860b821c","added_by":"auto","created_at":"2026-01-28 01:22:09","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":27927395,"visible":true,"origin":"","legend":"Supplementary Information","description":"","filename":"SupplementaryInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-8531730/v1/793d302bbd15d618804c7d8e.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Interface-directed charge regulation enables efficient perovskite/organic hybrid tandem LEDs","fulltext":[{"header":"Introduction","content":"\u003cp\u003eTandem light-emitting diode (LEDs) architectures, in which multiple electroluminescent units are electrically connected in series, represent a promising route to simultaneously enhance efficiency, brightness, and operational stability beyond the intrinsic limits of single-emissive devices.\u003csup\u003e\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e By distributing the operating voltage across multiple subunits, tandem designs can suppress current-induced degradation and reduce efficiency roll-off, making them attractive for high-brightness and high-resolution display applications. To date, tandem concepts have been extensively explored in organic light-emitting diodes (OLEDs) and quantum-dot light-emitting diodes (QLEDs), achieving impressive performance improvements. However, despite substantial progress in organic/organic and quantum-dot/quantum-dot tandem LEDs, conventional tandem approaches often face challenges such as broadband emission, complex multilayer solution processing, and strict solvent orthogonality requirements, which complicate device fabrication and limit material compatibility.\u003csup\u003e\u003cspan additionalcitationids=\"CR5 CR6\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eHybrid tandem LEDs that integrate a solution-processed QLED subunit with a vacuum-deposited OLED subunit have recently emerged as a promising alternative to overcome these limitations.\u003csup\u003e\u003cspan additionalcitationids=\"CR9 CR10 CR11\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e By combining the narrow emission bandwidth and spectral tunability of colloidal quantum dots with the mature device architectures and charge-transport materials of OLEDs, hybrid tandem designs offer a feasible pathway toward high-performance emission without severe solvent-induced damage to underlying layers. In particular, hybrid near-infrared (NIR) tandem LEDs are appealing for applications such as optical communication, night-vision displays, and bioimaging, where high radiance and spectral purity are required.\u003csup\u003e\u003cspan additionalcitationids=\"CR14 CR15 CR16 CR17\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e Despite these advantages, the practical implementation of hybrid tandem LEDs remains challenging, and their performance has not yet reached the theoretical expectations of ideal voltage and efficiency additivity.\u003c/p\u003e \u003cp\u003eThe development of hybrid tandem LEDs is fundamentally limited by the intrinsic electroluminescent mismatch between QLED and OLED subunits. Owing to their fundamentally different emission mechanisms, charge-transport mechanisms, recombination dynamics, and efficiency roll-off behaviors, QLEDs and OLEDs typically exhibit distinct current density\u0026ndash;voltage\u0026ndash;radiance characteristics.\u003csup\u003e\u003cspan additionalcitationids=\"CR20 CR21 CR22 CR23\" citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e When such subunits are electrically connected in series, this mismatch leads to severe current-driving imbalance, where one subunit operates away from its optimal efficiency regime while the other dominates the current flow. As a consequence, hybrid tandem devices often suffer from non-additive electroluminescent performance, emission imbalance, and compromised operational stability, particularly under high current densities required for practical applications. Addressing this intrinsic current-driving imbalance is therefore essential for realizing efficient and stable hybrid tandem LEDs.\u003c/p\u003e \u003cp\u003eIn this work, we address this challenge by selectively enhancing carrier injection and transport in the weaker NIR QLED subunit to achieve balanced current driving with an efficient NIR OLED subunit. Through targeted molecular engineering of the electron-transporting layer and rational design of the charge-generation interface, the electrical characteristics of the QLED are systematically tuned to better match those of the OLED. This strategy enables efficient series integration of the two emissive units, leading to near-ideal voltage addition and substantially improved electroluminescent performance in hybrid NIR tandem LEDs with EQE of 35% at 780 nm. Our results establish a general design principle for overcoming current-driving imbalance in hybrid tandem architectures and provide a viable route toward high-efficiency, spectrally pure NIR light sources.\u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cp\u003eFAPbI\u003csub\u003e3\u003c/sub\u003e-based perovskite nanocrystals and a Pt(II) complex emitter (Dph-3-f) were employed as representative near-infrared emissive materials for the QLED and OLED subunits, respectively. These two emissive systems exhibit comparable NIR emission wavelengths centered at approximately 780 nm and are based on well-established device architectures, enabling a meaningful comparison in hybrid tandem integration (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea).\u003c/p\u003e \u003cp\u003eDespite their spectral similarity, the QLED and OLED display markedly different current density\u0026ndash;efficiency characteristics, leading to emitting imbalance. As shown in \u003cb\u003eFigure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e\u003c/b\u003e, the NIR QLED reaches its peak external quantum efficiency (EQE) of 19.5% at a low current density of ~\u0026thinsp;0.05 mA cm\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e and undergo a serious efficiency roll of (EQE of 8.2% at 10 mA cm\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e and EQE of 5.6% at 50 mA cm\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e), while the NIR OLED achieves its peak EQE of 14.6% at a higher current density (~\u0026thinsp;0.1 mA cm\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e) and undergo a milder efficiency roll off (EQE of 11.2% at 10 mA cm\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e and EQE of 7.5% at 50 mA cm\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e). The fast efficiency drop of the QLED unit making the QLED a dominant to a weaker subunit, leading to spectral shift, incomplete stacking of emission and severe efficiency roll-off in the tandem LEDs. The electroluminescent of tandem demonstrated that simply combining the two units together only reach a peak EQE of 28%, far below the summed performance of the individual subunits.\u003c/p\u003e \u003cp\u003eThus, mitigating the efficiency roll-off of the weaker subunit is essential for improving current-driving balance between the subunits and enhancing the overall tandem efficiency.\u003c/p\u003e \u003cp\u003eWe attribute the pronounced efficiency roll-off observed in the NIR QLED unit primarily to the limited electron injection and transport characteristics of the electron-transporting layer (ETL).\u003csup\u003e\u003cspan additionalcitationids=\"CR26 CR27 CR28 CR29\" citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e While the multiple phosphine oxide groups in 2,4,6-tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine (POT2T) based ETL are effective in passivating surface defects of perovskite nanocrystals and provide a suitable lowest unoccupied molecular orbital (LUMO) energy level for charge injection, its three-dimensional molecular configuration introduces significant steric hindrance, which disrupts continuous π-conjugation between neighboring molecules and weakens intermolecular electronic coupling.\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e,\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e Besides, due to its amorphous nature, POT2T forms a disordered ETL/QDs interface with poor molecular packing, which further reduces electron mobility (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). Especially under high current density, the limited electron transport results in the serious imbalance between electron and hole injection, leading to inefficient recombination and hole leakage at the ETL/QD interface (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo overcome these limitations, we designed a linearly structured ETL (ANPO) with a rigid backbone and extended π-conjugation (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). Compared with the bulky 3D configuration of POT2T, the linear and planar geometry of ANPO enables extended π-conjugation along the molecular axis, promoting stronger π-π stacking between adjacent molecules.\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e This ordered stacking forms continuous electronic pathways, greatly enhancing electron delocalization and intermolecular orbital overlap, which in turn increases electron mobility. The symmetrical phosphine oxide anchoring groups not only stabilize the LUMO energy level but also strengthen the interaction with QDs, ensuring a uniform and well-aligned ETL/QD interface. This optimized packing suppresses interfacial disorder, reduces trap-assisted recombination, and facilitates rapid electron injection into the QDs. As a result, ANPO can effectively balance electron and hole currents, minimize interfacial charge accumulation, and significantly reduce efficiency roll-off in QLED-based tandem devices (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec).\u003c/p\u003e \u003cp\u003eTo verify the improved π-π stacking of ANPO, we first investigated the two-dimensional grazing-incidence wide-angle X-ray scattering (GIWAXS) of the two ETL films (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). The POT2T film exhibited featureless, diffuse scattering halos, indicating a predominantly amorphous structure with no long-range molecular order. In contrast, the ANPO film displayed distinct diffraction rings, particularly along the out-of-plane direction at \u003cem\u003eq\u003c/em\u003e\u0026thinsp;\u0026asymp;\u0026thinsp;1.7 \u0026Aring;\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, corresponding to a d-spacing of approximately 3.7 \u0026Aring;.\u003csup\u003e34\u0026ndash;36\u003c/sup\u003e This diffraction feature is characteristic of \u003cb\u003eπ-π stacking interactions\u003c/b\u003e between adjacent conjugated backbones. Besides, the ANPO film exhibits longer crystal coherence length (\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003ec\u003c/em\u003e\u003c/sub\u003e), which is 24.1 \u0026Aring; compared to 21.6 \u0026Aring; of the POT2T film (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ee). This indicates that ANPO forms more extended crystalline domains with higher structural coherence along the stacking direction, reflecting better molecular packing continuity and fewer lattice defects. AFM and SEM analyses further reveal that ANPO forms a more uniform film morphology, exhibiting a smaller surface roughness of 2.61 nm compared with 3.27 nm for POT2T (\u003cb\u003eFigure S2,3\u003c/b\u003e).\u003c/p\u003e \u003cp\u003eWe then performed the spectroscopic characterizations of the two ETLs. Both absorption and PL spectra of the ANPO film are redshifted compared with those of the POT2T film (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ef). The optical bandgap of the ANPO film is 3.0 eV, which is smaller than POT2T (3.97 eV). Combined with UPS spectra (\u003cb\u003eFigure S4\u003c/b\u003e), the LUMO onset energy is \u0026minus;\u0026thinsp;3 eV for ANPO, which is ~\u0026thinsp;0.4 eV lower than the POT2T, facilitating the electron injection (\u003cb\u003eFigure S5\u003c/b\u003e).\u003c/p\u003e \u003cp\u003eTo gain deeper insights into the ETL/QD interface and carrier injection, we performed density functional theory (DFT) calculations to examine the interaction between ETLs and the QDs. The total electron density difference maps clearly visualize how the ETLs interact with the QDs (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea,b). For ANPO, its symmetrical phosphine oxide anchoring groups strengthen binding to the QDs and drive the formation of an ordered planar geometry, which facilitates efficient interfacial charge transfer. We also investigated the surface electrostatic potential (ESP) of two molecules (\u003cb\u003eFigure S7\u003c/b\u003e). POT2T typically has low ESP (green) near the edges and negative (red) regions are typically hindered by the nearby phenyls, making it a worse candidate for perovskite attachment.\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e On the contrary, the linear structure and the presence of oxygen atoms in ANPO creates regions of negative potential, enabling its effective attachment to Pb atoms of the perovskite. We then analyzed the charge displacement profiles along the z-axis and found that ANPO creates a larger disparity in electron cloud distribution, generating a stronger internal electric field that accelerates electron transfer and injection.\u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e,\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e In contrast, the POT2T/QD interface exhibits localized charge transfer, and the multiple phosphine oxide groups induce a distorted, nonplanar adsorption geometry that hinders electron transport.\u003c/p\u003e \u003cp\u003eWe then investigated charge recombination dynamics using time-resolved electroluminescence (TREL) and photoluminescence (TRPL) test for different ETLs. The faster rise-time of the ANPO in TREL spectrum demonstrates the better carrier injection and recombination (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed).\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e,\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e We also employed TRPL to probe the carrier recombination dynamics of QD films deposited on different ETL layers. The PL decay of the QDs on ANPO exhibits a noticeably shorter average lifetime compared with that on POT2T (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee). This faster decay indicates more efficient electron extraction from the QDs to the ETL, suggesting that ANPO provides a better interfacial charge-transfer pathway. We further measured electron mobilities via space-charge-limited current (SCLC) in electron-only devices (\u003cb\u003eFigure S8\u003c/b\u003e) (ITO/LiF (1 nm)/ETL (100 nm)/LiF (1 nm)/Al (100 nm)) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef). ANPO-based devices exhibits a much higher current density than the POT2T and a faster electron mobilities of 1.0 \u0026times; 10\u003csup\u003e\u0026ndash;3\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e V\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e s\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e compared to 4.8 \u0026times; 10\u003csup\u003e\u0026ndash;5\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e V\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e s\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e for POT2T under an electric field of 6.4 \u0026times; 10\u003csup\u003e5\u003c/sup\u003e V cm\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, which is comparable to hole mobility of PEDOT:PSS (5.76 \u0026times; 10\u003csup\u003e\u0026ndash;4\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e V\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e s\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e ).\u003csup\u003e41\u003c/sup\u003e Finally, we performed the Kelvin probe force microscopy (KPFM), and found the ANPO delivers a larger work function compared to POT2T (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eg,h) and a narrower CPD distribution (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ei), indicating a stronger and more homogeneous surface charge transfer.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo test the interaction between different ETLs and QDs, we then performed Fourier transform infrared (FTIR) (\u003cb\u003eFigure S9\u003c/b\u003e). The emergence of C-P symmetric (1410 cm\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e) demonstrated the attachment of both the ETLs on QDs surface.\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e Besides, Pb\u003csup\u003e2+\u003c/sup\u003e coordination passivation via P\u0026thinsp;=\u0026thinsp;O bonds was evidenced by pronounced shifts to lower binding energy of Pb 4\u003cem\u003ef\u003c/em\u003e through XPS spectrum (\u003cb\u003eFigure S10\u003c/b\u003e). Furthermore, the trap filled limit voltage (V\u003csub\u003eTFL\u003c/sub\u003e) were tested through electron-only devices (\u003cb\u003eFigure S11\u003c/b\u003e). The V\u003csub\u003eTFL\u003c/sub\u003e for ANPO is 0.74 V, which is much lower than that of the POT2T (1.07 V). It was attributed to the better surface defects passivation of ANPO. This is consistent to trap density of states (tDOS) (\u003cb\u003eFigure S12\u003c/b\u003e), which prove the better defect passivation of the ANPO, and drive-level capacitance profiling (DLCP) test, demonstrating better trap passivation on the QDs/ETL surface.\u003c/p\u003e \u003cp\u003eTo demonstrate the QLED with ANPO whether reach a better current-driving balance with the OLED, we fabricated NIR QLEDs with the structure ITO/PEDOT:PSS/Poly-TPD/QDs/ANPO or POT2T/Liq/Al (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea,b). The QLEDs emitting efficient NIR light at 780 nm with no distinct EL shift under bias from 1.6 to 6 V (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec). The current density-voltage-radiance (J-V-R) curves (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed) show that ANPO-based devices exhibit a markedly higher current density than POT2T-based QLEDs, indicating enhanced charge injection. ANPO also boosts radiance performance by nearly threefold, delivering a maximum radiance of 35 W sr\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e m\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e compared to 12 W sr\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e m\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e for POT2T. The optimized ANPO-based QLED achieves a peak EQE of 21% at 1 mA cm\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e, while sustains 9.8% EQE at 100 mA cm\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e (4.1% of control sample), further confirming its efficiency advantage (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee). Besides, the Capacitance-voltage measurements show that the ANPO-based LED exhibits a lower overall capacitance and a much smaller, narrower peak than the control device (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef). This indicates reduced interfacial charge storage and trap filling, consistent with more efficient electron extraction and faster transport through the ANPO ETL. The superior performance of ANPO originates from its optimized molecular geometry, as revealed by DFT calculations. The linear backbone and symmetrical phosphine oxide anchoring groups promote ordered planar adsorption on the QD surface, yielding a uniform charge-transfer distribution across the ETL/QD interface. With the great improve in efficiency foll-off, we compared the EL behavior between two QLEDs and the OLED unit (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed). The curve of J-EQE of the QLED with ANPO perfectly contain the OLED curve, demonstrating better current-driving balance between the two subunits. We further evaluated operational stability by monitoring luminance decay at 1 mA cm\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef). The T\u003csub\u003e50\u003c/sub\u003e values are 82 min for POT2T-based QLEDs and 282 min for ANPO-based QLEDs, representing a 3.5-fold lifetime improvement. Collectively, these results indicate that the modified QLED is now fully compatible for tandem integration with the OLED.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFinally, we integrated the improved ANPO-based QLEDs into a hybrid tandem LED, in which the QLED and OLED units were vertically stacked and connected through Bphen:LiNH\u003csub\u003e2\u003c/sub\u003e and mCP:MoO\u003csub\u003e3\u003c/sub\u003e, which serve as the charge generation layer. The energy band diagram of the hybrid device was constructed using energy level values from reported literature. The top OLED, with the structure ITO/HAT-CN/MoO\u003csub\u003e3\u003c/sub\u003e:CBP/CBP/Dph-3-f/CNT2T/LiF/Al, also emitted NIR light with a peak at 786 nm, closely matching the QLED emission (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea,b).\u003c/p\u003e \u003cp\u003eThanks to the suppression of efficiency roll-off and improved carrier balance in the optimized QLED sub-unit, the tandem device fully exploits the combined efficiencies of both emissive units. The current density-voltage (J-V) and radiance-voltage (R-V) curves reveal slower current injection for the hybrid device with POT2T due to the larger series resistance from multiple stacked layers (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec). Nevertheless, the hybrid tandem with ANPO reaches a radiance of 82 W sr\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e m\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e, demonstrating 1.7-fold improvement of that with POT2T. Most notably, it achieves a peak EQE of 35% (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed), nearly the sum of the individual QLED (21%) and OLED (14.6%) EQEs (\u003cb\u003eFigure S13\u003c/b\u003e), confirming highly efficient carrier generation, injection, and recombination in the tandem LEDs with ANPO. While the tandem with POT2T only exhibits EQE of 28%, greatly lowing than the sum of control QLED (19.5%) and OLED (14.6%), demonstrating the current driving imbalance. Besides, from the EL spectrum, we can find that the EL peak of the tandem with POT2T shifts greatly with the increase of the external bias, demonstrating the dominant subunit of the tandem shift from the QLED to the OLED (\u003cb\u003eFigure S14.a\u003c/b\u003e). While the tandem with ANPO exhibits consistent emission, demonstrating the balance between the QLED and the OLED in the optimized tandem device (\u003cb\u003eFigure S14.b\u003c/b\u003e). This value represents one of the record EQE for NIR LEDs (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eHybird tandem LEDs is no doubt a proming solution to the limitaion of efficient NIR LEDs. From the materials aspects, it greatly broaden the materials selection for the tandem LEDs, providing thousands of possible combinations among different types of materials. From the device fabrication aspect, it does not need complex fabrication technique and worry about solvent miscibility issue, and can be integrated into well-established manufacturing process of OLEDs. Due to the intrinsic difference of the two types of emissive materials, we demonstrated modulation the current-driving balance of the two types is very important in improving hybrid tandem LEDs efficiency. Furthermore, we expected additional improvement will be realized through the optical simulation and cavity-length optimization to reduce optical absorption and scattering, especially in a multilayer device structure that contain organic and inorganic materials. We expect hybrid tandem device to open a new avenue for bridging different types of emissive materials and to leverage their respective advantages for efficient electroluminancet performance.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eWe demonstrate that molecular-level ETL engineering enables NIR QLEDs to operate as viable tandem sub-units. By designing ANPO with a linear rigid backbone and symmetrical P\u0026thinsp;=\u0026thinsp;O anchoring groups, we achieve a more ordered QD/ETL interface, promote π-π stacking, and markedly enhance electron delocalization. These advances translate directly to devices: ANPO-based NIR QLEDs deliver EQEₘₐₓ of 21.2% and radiance of 35 W sr\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e m\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e, while sustaining 9.8% EQE at 100 mA cm\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e (4.1% of control sample) and exhibiting a 3.5-fold lifetime extension. Furthermore, the improved QLED sub-unit spectrally and electrically matches a NIR OLED (Dph-3-f), enabling a hybrid tandem LED with a record EQE of 35%. Our results show that interface-ordering ETLs overcome the practical limitations of scarce, high-performance NIR emitters and unlock tandem architectures capable of achieving true performance additivity.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAcknowledgement\u003c/h2\u003e \u003cp\u003eThis work was supported by the National Natural Science Foundation of China (NSFC) (U25A20523, 62175171, 62375193, 62474119, and 62522514), Gusu Innovation and Entrepreneurship Leading Talent Program (ZXL2024367), National Key Research and Development Program of China (2024YFA1209500), Collaborative Innovation Center of Suzhou Nano Science \u0026amp; Technology (NANO-CIC), Suzhou Key Laboratory of Functional Nano \u0026amp; Soft Materials, the 111 Project, Joint International Research Laboratory of Carbon-Based Functional Materials and Devices.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eChen A et al (2020) Highly efficient tandem blue phosphorescent organic LEDs with external quantum efficiency exceeding 42%. 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Nat Commun 12:5081. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1038/s41467-021-25407-8\u003c/span\u003e\u003cspan address=\"10.1038/s41467-021-25407-8\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"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-8531730/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8531730/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eNear infrared (NIR) light-emitting devices hold significant promise for applications in night vision, telecommunications, and biomedical imaging. Hybrid tandem light-emitting diodes (LEDs) that combine quantum-dot (QD)-based and organic emissive subunits represent a compelling strategy to surpass an external quantum efficiency (EQE) of 30%. However, in series-connected architectures, the intrinsic mismatch in charge-transport properties and distinct efficiency roll-off characteristics between the two emissive units hinder ideal efficiency summation and limit overall device performance under identical current injection. Here, we report a high-performance hybrid NIR tandem LED in which this imbalance is mitigated by selectively enhancing carrier injection and transport in the performance-limiting QD-based emissive unit. Through molecular engineering of the electron-transporting layer and rational design of the charge-generation interface, the electrical characteristics of the QD unit is precisely tailored to match that of the high-efficiency organic NIR emitter. As a result, the hybrid tandem device achieves a near-ideal voltage addition and markedly improved electroluminescence, delivering a peak external quantum efficiency of 35% with stable emission at 780 nm. This work establishes a general design principle for overcoming current-driving imbalance in heterogeneous tandem architectures and paves the way toward high-performance NIR light sources.\u003c/p\u003e","manuscriptTitle":"Interface-directed charge regulation enables efficient perovskite/organic hybrid tandem LEDs","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-28 01:22:02","doi":"10.21203/rs.3.rs-8531730/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"dfeef28d-dde5-4ec2-b499-6db9356886bb","owner":[],"postedDate":"January 28th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":61723949,"name":"Physical sciences/Optics and photonics/Lasers, LEDs and light sources"},{"id":61723950,"name":"Physical sciences/Materials science/Materials for optics/Lasers, LEDs and light sources"}],"tags":[],"updatedAt":"2026-03-19T06:05:38+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-28 01:22:02","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8531730","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8531730","identity":"rs-8531730","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}