{"paper_id":"2a4dd9ed-1d7e-4f95-8f96-4ddbab93bb4e","body_text":"One-step fabricated ZnO electron-transporting layers for perovskite light-emitting diodes with sub-bandgap turn-on voltage | 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 Research Article One-step fabricated ZnO electron-transporting layers for perovskite light-emitting diodes with sub-bandgap turn-on voltage XINZHI SUN, JIALIN BAI, TING WANG, HANZHUANG ZHANG, WENYU JI This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3874292/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 08 May, 2024 Read the published version in Applied Physics B → Version 1 posted 8 You are reading this latest preprint version Abstract Efficient charge injection into the emitters, which can reduce the voltage loss at interfaces, is a prerequisite for high-performance light-emitting diodes, with low voltage operation. Here we develop a sol-gel ZnO (s-ZnO) electron-transport layer for the perovskite light-emitting diodes (PeLEDs) with green-emission formamidinium lead bromide (FAPbBr 3 ) perovskites as emitters. Polyethylenimine (PEI) is mixed into the s-ZnO precursor as a modifier, which not only promotes the wettability of s-ZnO films, but also passivates the defects of s-ZnO without sacrificing their electrical conductivity. As a result, highly efficient FAPbBr 3 films are obtained on the s-ZnO films. The maximum current efficiency of PeLED with s-ZnO:PEI electron-transporting layer reaches 13.5 cd/A, 45% higher than that based on pristine s-ZnO without PEI modifier. Benefiting from the outstanding charge-transport properties of s-ZnO and high-quality perovskite film, the turn-on voltage of the s-ZnO based PeLEDs is only 1.9 V, much lower than the band-gap voltage (~ 2.3 V) of FAPbBr 3 . Figures Figure 1 Figure 2 Figure 3 Figure 4 1. Introduction Metal halide perovskite light-emitting diodes (PeLEDs) have gained much attraction due to their unique photoelectrical properties such as high photoluminescence (PL) quantum yield [ 1 ], excellent color purity [ 2 ], and low-cost solution processing [ 3 ]. Currently, the external quantum efficiency of the PeLEDs has exceeded 20% [ 4 , 5 ], a theory limitation for conventional planar light-emitting diodes. However, the ion migration under high driving voltage remains a huge challenge to the stability of PeLEDs [ 6 – 8 ], which could be mitigated by lowering the driving voltage through optimizing various functional layers. Recently, PeLEDs turned on at sub-bandgap voltage have been reported by Liao et al . [ 9 ]. Di et al. proposed that the sub-bandgap electroluminescence (EL) turn-on behavior is attributed to the radiative recombination of non-thermal-equilibrium band-edge charge carriers [ 10 ]. In this scenario, the voltage losses at charge-transport layers and interfaces must be reduced as much as possible to achieve EL emission at ultralow driving voltages. Therefore, highly conductive (which means high carrier mobility or/and carrier density) and Ohmic contact available charge-transport/injection layers are indispensable. At the same time, it is crucial to prevent significant emission reduction caused by the charge-transport layers to achieve efficient light emission from the perovskite emitters. Metal oxide films are promising charge-transport layers satisfying the above-mentioned requirements, which have been used as the electron- and hole-transport layers in organic LEDs, quantum-dot LEDs, and PeLEDs [ 11 ]. Amorphous ZnO films are very popular electron-transport layers (ETLs) due to their outstanding optoelectrical properties and resistance to the organic solvents used for depositing perovskite films [ 12 – 14 ]. Compared with the ETL obtained by the preformed ZnO nanoparticles, in - situ sol-gel ZnO (s-ZnO) films have more advantages, including low cost and accessibility for regulating their optoelectrical properties by adding additive into the precursor solution [ 15 ]. Although the ZnO films have excellent electrical properties, their quenching effect on the emission of perovskite emissive layers is harmful to the device performance, which is intensified by the defects on the ZnO surface. Therefore, surface modification for the ZnO films is essential to suppress these non-radiative processes of the perovskites. It has reported that this emission quenching effect is partially hindered by inserting an interlayer between ZnO and perovskite layer, such as polyethyleneimine (PEI) and its derivative polyethylenimine ethoxylated (PEIE) [ 16 , 17 ]. However, the above-mentioned modification method typically requires two successive solution spin-coating processes, and damage to the underlying film by the upper-layer solution is inevitable. Besides, the device performance of PeLEDs, is rather sensitive to the thickness of these interlayers due to their insulation characteristics [ 18 – 20 ], These factors lead to poor reproducibility of well-performing devices. In this work, PeLEDs are fabricated by employing a s-ZnO:PEI film as the ETL to address the sensitivity of device repeatability to the forming factors of PEI or PEIE modifying layers. The PEI additive not only improves the wettability, but also passives defects of s-ZnO films (named as s-ZnO:PEI). This synergistic effect of PEI results in high-quality perovskite films on the s-ZnO:PEI ETL and suppresses emission quenching effect of the perovskite emitters. Consequently, a PeLED with the turn-on voltage as low as 1.9 V is obtained. Moreover, the peak current efficiency of the PeLED reaches 13.5 cd/A, 45% higher than that based on pristine s-ZnO ETL. 2. Results and discussion It is well known that the crystal quality of in - situ fabricated perovskite films is closely related to the surface properties of the target substrates. The wettability of the s-ZnO with and without PEI modifier is characterized and the results are shown in Figs. 1 a, b. The contact angle for the DMF drop on s-ZnO:PEI film is smaller than that on the pristine s-ZnO film, which suggests the wettability of s-ZnO is improved with the introduction of PEI. Therefore, the s-ZnO:PEI films are more suitable for in - situ fabrication of perovskite films. The surface morphology of these ZnO films is evaluated in terms of scanning electron microscopy (SEM, acquired by scanning electron microscope, Regulus 8100) measurements. A completely covered and uniform s-ZnO film is obtained on the ITO substrate as can be observed from Fig. 1 c. Moreover, the quality of the s-ZnO film is further improved by the doping of PEI in the ZnO precursor solution as shown in Fig. 1 d. The morphology properties of perovskite layers on different ZnO substrates are characterized by atomic force microscope (AFM, CoreAFM, nanosurf) measurements. The perovskite film deposited on the pristine s-ZnO layer is very uniform and smooth with root mean square (RMS) value of 1.48 nm (Fig. 1 e). In comparison, the surface roughness is reduced to 1.27 nm for the perovskite film deposited on the s-ZnO:PEI film (Fig. 1 f). The reduced surface roughness is conductive to limiting the leakage current across the devices. Figure 2 shows the optical properties and crystal structure information of two perovskite films deposited on the s-ZnO and s-ZnO:PEI films. These two perovskite films display identical PL and absorption spectra as shown in Fig. 2 a, including emission/absorption peaks and profile, which mean that the perovskites share similar microstructure. The X-ray diffraction (XRD, measured by a R-AXIS-RAPID II) patterns shown in Fig. 2 b verify that these two perovskite films indeed possess the same crystal structure and particle size. The characteristic peaks of FAPbBr 3 films locate at 14.8°, 21.2°, 29.5° and 33.4°, corresponding to the (100), (110), (200) and (210) planes of cubic FAPbBr 3 crystal, respectively. These results imply that the PEI may have no influence on the perovskite growth. Nevertheless, the transient PL decays (measured through a HORIBA, IHR320) of these two perovskite films manifest that the perovskite deposited on the s-ZnO:PEI film possesses longer PL lifetime than that obtained on the pristine s-ZnO film, as shown in Fig. 2 c. This extension of PL lifetime is due to PEI passivating the defects in s-ZnO, inhibiting PL quenching of perovskite, rather than reducing the defects in perovskite, which will be confirmed below. The passivation mechanism of s-ZnO by PEI is shown in Fig. 2 d as further discussed below. In order to verify that PEI passivates the defects in s-ZnO, we measured the XPS (X-ray Photoelectron Spectroscopy, thermo scientific NEXSA) of s-ZnO and s-ZnO:PEI films. As shown in Fig. 3 a, the O 1s core level spectra recorded from the pristine s-ZnO can be deconvoluted into three main subpeaks located at 530.1 eV, 531.4 eV and 532.0 eV, which can be attributed to Zn–O bonds, oxygen vacancies, and chemisorbed oxygen species such as hydroxyl (OH − ), respectively [ 21 ]. After adding PEI, the peak strength of 531.4 eV is significantly reduced as shown in Fig. 3 b, indicating that the defects are passivated. In addition, the binding energies of Zn 2p 1/2 and Zn 2p 3/2 in s-ZnO:PEI are 1045.4 eV and 1022.3 eV respectively, which is 0.6 eV higher than that of s-ZnO (1044.8 eV and 1021.7 eV, respectively) as shown in Fig. 3 c, d. This should be caused by the interaction between PEI molecule and Zn ion. To verify the feasibility of s-ZnO as the ETL, PeLEDs are built by employing an inverted device structure consist of indium tin oxide (ITO) coated glass/ETL (~ 40 nm)/FAPbBr 3 (~ 50 nm)/poly [9-vinylcarbazole] (PVK, ~ 30 nm)/MoO 3 (~ 8 nm)/Al (~ 100 nm) as depicted in Fig. 4 a. The s-ZnO and FAPbBr 3 films were fabricated according to previous reports [ 15 , 22 ]. To fabricate s-ZnO:PEI ETL, the precursor of s-ZnO precursor solution is mixed with PEI (1 wt.% in DMF) according to volume ratio of 1:2. The PVK solution (8 mg/ml in CB) layers were spin-coated on the perovskite layer at 3000 rpm for 60 s in a glove box and then annealed at 80°C for 15 min. Finally, these samples were transferred into a vacuum evaporation chamber jointed with the glove box to deposit the MoO 3 and Al layers under pressure of below 4×10 − 5 Pa. The photoelectric properties of PeLEDs were measured as described in our previous work [ 23 ]. Figure 4 b shows the current density‒voltage‒luminance ( J ‒ V ‒ L ) curves of the PeLEDs based on s-ZnO and s-ZnO:PEI ETLs. These two J ‒ V curves share similar profile, especially for the trap-filled limit voltage ( V TFL ) [ 24 ], which implies that the density of traps ( N trap ) in these two perovskite films is similar according to space-charge-limited current (SCLC) theory ( N trap =2 εε 0 V TFL / q · L 2 , ε 0 is vacuum permittivity and ε is the dielectric constant of the perovskite film, q is the elementary charge, and L is the thickness of perovskite film) [ 25 ]. These results further verify that the different PL lifetimes of perovskites deposited on s-ZnO and s-ZnO:PEI are due to the PL quenching effects induced by ZnO rather than the defects in perovskite films. However, the s-ZnO:PEI bases PeLED exhibits lower current densities than that of device with pristine s-ZnO as the ETL. This is attributed tothe insulating properties of the PEI and smoother perovskite films (Fig. 1 f). These two devices show the same turn-on voltage (defining the driving voltage when the device luminance is 0.1 cd/m 2 ) and almost identical luminance within the whole driving voltage range. The same V ‒ L properties indicate that the PEI does not affect the electron injection capability of s-ZnO ETL. It worth noting that these two devices can be turned on at sub-bandgap voltage (1.9 V at 0.1 cd/m 2 , much lower than the optical bandgap of FAPbBr 3 divided by the elementary charge q , ~ 2.3 V) as reported previously [ 26 ]. The radiative recombination of the non-thermal-equilibrium carriers induced by a small external bias is responsible to the sub-bandgap EL onset, rather than other high-order effect as reported recently [ 9 ]. Due to the similar of these two PeLEDs, s-ZnO:PEI based device possesses higher current efficiency of 13.5 cd/A, 45% higher than that of s-ZnO device (9.3 cd/A) as shown in Fig. 4 c. The efficiency enhancement is attributed to the suppressed quenching effect due to the addition of PEI molecules. The EL spectra of these two devices are shown in Fig. 4 d. Pure EL emissions completely from the perovskites without any contribution from adjacent layers confirms that the excitons are dominantly formed in the perovskite layers. The photograph shown in the inset of Fig. 4 d is the s-ZnO:PEI PeLED working at voltage of 3.0 V, which displays a vivid green emission. We attribute the enhanced device performance to the passivation effect of PEI to the defects of ZnO. 3. Conclusion In summary, PeLED was prepared by using s-ZnO as ETL. Thanks to the improved wettability of s-ZnO films by the PEI modifier, high-quality FAPbBr 3 perovskite films were obtained with high coverage on the s-ZnO:PEI films. Moreover, the passivation of s-ZnO induced by the PEI molecules protects the perovsktie emitters from the quenching effect of defects in s-ZnO. Combining with the outstanding conductive properties of s-ZnO, excellent PeLEDs with low operation voltage are achieved. The peak current efficiency reaches 13.5 cd/A, and the driving voltage is 1.9 V at luminance of 0.1 cd/m 2 for the PEI-containing PeLEDs. The results of this study confirm the feasibility of s-ZnO as ETL for PeLED, and provide a reference and idea for preparing more efficient PeLED. Declarations Disclosures. The authors declare no conflicts of interest. Funding. This work was supported by the program of the National Natural Science Foundation of China (Nos. 12374375, 12274173 and 12074148). Author Contribution All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by [XinZhi Sun], [JiaLin Bai], [Ting Wang], [HanZhuang Zhang] and [WenYu Ji] . The first draft of the manuscript was written by [XinZhi Sun] and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Data Availability. Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request. References X. G. Wu, J. Tang, F. Jiang, X. Zhu, Y. Zhang, D. Han, L. Ling, and H. Zhong, “Highly luminescent red emissive perovskite quantum dots-embedded composite films: Ligands capping and caesium doping-controlled crystallization process,” Nanoscale. 11, 4942 (2019). H. Cho, J. S. Kim, C. Wolf, Y. H. Kim, H. J. Yun, S. H. Jeong, A. Sadhanala, V. Venugopalan, J. W. Choi, C. L. Lee, R. H. Friend, and T. W. Lee, “High-Efficiency Polycrystalline Perovskite Light-Emitting Diodes Based on Mixed Cations,” ACS Nano. 12, 2883 (2018). N. Wang, L. Cheng, R. Ge, S. Zhang, Y. Miao, W. Zou, C. Yi, Y. Sun, Y. Cao, R. Yang, Y. Wei, Q. Guo, Y. Ke, M. You, Y. Jin, Y. Liu, Q. Ding, D. Di, L. Yang, G. Xing, H. Tian, C. Jin, F. Gao, R. H. Friend, J. Wang, and W. Huang, “Perovskite light-emitting diodes based on solution-processed self-organized multiple quantum wells,” Nat. Photonics. 10, 699 (2016). Y. Cao, N. Wang, H. Tian, J. Guo, Y. Wei, H. Chen, Y. Miao, W. Zuo, K. Pan, Y. He, H. Cao, Y. Ke, M. Xu, Y. Wang, M. Yang, K. Du, Z. Fu, D. Kong, D. Dai, Y. Jin, G. Li, H. Li, Q. Peng, J. Wang, and W. Huang, “Perovskite light-emitting diodes based on spontaneously formed submicrometre-scale structures,” Nature. 562, 249 (2018). K. Lin, J. Xing, L. N. Quan, F. P. G. Arquer, X. Gong, J. Lu, L. Xie, W. Zhao, D. Zhang, C. Yan, W. Li, X. Liu, Y. Lu, J. Kirman, E. H. Sargent, Q. Xiong, and Z. Wei, “Perovskite light-emitting diodes with external quantum efficiency exceeding 20 per cent,” Nature. 562, 245 (2018). N. Li, L. Song, Y. Jia, Y. Dong, F. Xie, L. Wang, S. Tao, and N. Zhao, “Stabilizing Perovskite Light-Emitting Diodes by Incorporation of Binary Alkali Cations,” Adv. Mater. 32, e1907786 (2020). L. Zhang, F. Yuan, J. Xi, B. Jiao, H. Dong, J. Li, and Z. Wu, “Suppressing ion Migration Enables Stable Perovskite Light-Emitting Diodes with All-Inorganic Strategy,” Adv. Funct. Mater. 30, 2001834 (2020). K. Anil. Y. Natalia, F. Yan, T. J. N. Hooper, P. J. S. Rana, F. Benny, P. C. Harikesh, S. Teddy, V. Parth, S. G. Mhaisalkar, and M. Nripan, “Stabilizing the Electroluminescence of Halide Perovskites with Potassium Passivation,” ACS. Energy. Lett. 5, 6, 1804–1813 (2020). S. Yuan, Q. W. Liu, Q. S. Tian, Y. Jin, Z. K. Wang, and L. S. Liao, “Auger Effect Assisted Perovskite Electroluminescence Modulated by Interfacial Minority Carriers,” Adv. Funct. Mater. 30, 1909222 (2020). Y. Lian, D. Lan, S. Xing, B. Guo, Z. Ren, R. Lai, C. Zou, B. Zhao, R. H. Friend, and D. Di, “Ultralow-voltage operation of light-emitting diodes,” Nat. Commun. 13, 3845 (2022). C. Zang, S. Liu, M. Xu, R. Wang, C. Cao, Z. Zhu, J. Zhang, H. Wang, L. Zhang, W. Xie, and C. S. Lee, “Top-emitting thermally activated delayed fluorescence organic light-emitting devices with weak light-matter coupling,” Light Sci. Appl. 10, 116 (2021). Y. C. Kim, S.-D. Baek, and J.-M. Myoung, “Enhanced brightness of methylammonium lead tribromide perovskite microcrystal-based green light-emitting diodes by adding hydrophilic polyvinylpyrrolidone with oleic acid-modified ZnO quantum dot electron transporting layer,” J. Alloys Compd. 786, 11 (2019). C. Tang, X. Shen, X. Wu, Y. Zhong, J. Hu, M. Lu, Z. Wu, Y. Zhang, W. W. Yu, and X. Bai, “Optimizing the Performance of Perovskite Nanocrystal LEDs Utilizing Cobalt Doping on a ZnO Electron Transport Layer,” J. Phys. Chem. Lett. 12, 10112 (2021). C.-J. Chang and S.-H. Yang, “ZnO nanocrystals incorporating PEIE and a fluorene-based polyelectrolyte as electron transport layers for pure cesium-containing perovskite light-emitting devices,” Mater. Res. Express. 6, 105304 (2019). Y. Yuan, X. Xue, T. Wang, X. Chi, R. Wang, and W. Ji, “Polyethylenimine modified sol-gel ZnO electron-transporting layers for quantum-dot light-emitting diodes,” Org. Electron. 100, 106393 (2022). L. Meng, E. P. Yao, Z. Hong, H. Chen, P. Sun, Z. Yang, G. Li, and Y. Yang, “Pure Formamidinium-Based Perovskite Light-Emitting Diodes with High Efficiency and Low Driving Voltage,” Adv. Mater. 29, 1603826 (2017). Y. Zhu, X. Zhao, B. Zhang, B. Yao, Z. Li, Y. Qu, and Z. Xie, “Very efficient green light-emitting diodes based on polycrystalline CH(NH 3 ) 2 PbBr 3 film achieved by regulating precursor concentration and employing novel anti-solvent,” Org. Electron. 55, 35 (2018). V. Prakasam, F. Di Giacomo, R. Abbel, D. Tordera, M. Sessolo, G. Gelinck, and H. J. Bolink, “Efficient Perovskite Light-Emitting Diodes: Effect of Composition, Morphology, And Transport Layers,” ACS Appl. Mater. Interfaces. 10, 41586 (2018). L. Zhao, K. M. Lee, K. Roh, S. U. Z. Khan, and B. P. Rand, “Improved Outcoupling Efficiency and Stability of Perovskite Light-Emitting Diodes using Thin Emitting Layers,” Adv. Mater. 31, e1805836 (2019). Y. J. Jung, S. Y. Cho, J. W. Jung, S. Y. Kim, and J. H. Lee, “Influence of indium-tin-oxide and emitting-layer thicknesses on light outcoupling of perovskite light-emitting diodes,” Nano Convergence. 6, 26 (2019). Y. Lai, Z. Zeng, C. Liao, S. Cheng, J. Yu, Q. Zheng, and P. Lin, “Ultralow switching current in HfO x /ZnO bilayer with tunable switching power enabled by plasma treatment,” Appl. Phys. Lett. 109, 063501 (2016). D. Han, M. Imran, M. Zhang, S. Chang, X. G. Wu, X. Zhang, J. Tang, M. Wang, S. Ali, X. Li, G. Yu, J. Han, L. Wang, B. Zou, and H. Zhong, “Efficient Light-Emitting Diodes Based on in Situ Fabricated FAPbBr 3 Nanocrystals: The Enhancing Role of the Ligand-Assisted Reprecipitation Process,” ACS Nano. 12, 8808 (2018). Z. Liu, X. Xue, Z. Kang, R. Wang, H. Zhang, and W. Ji, “Achieving high-performance in situ fabricated FAPbBr 3 and electroluminescence,” Opt. Lett. 46, 4378 (2021). F. Cheng, R. He, S. Nie, C. Zhang, J. Yin, J. Li, N. Zheng, and B. Wu, “Perovskite Quantum Dots as Multifunctional Interlayers in Perovskite Solar Cells with Dopant-free Organic Hole Transporting Layers,” J. Am. Chem. Soc. 143, 5855 (2021). R. H. Bube, “Trap Density Determination by Space-Charge-Limited Currents,” J. Appl. Phys. 33, 1733 (1962). G. Mannino, I. Deretzis, E. Smecca, A. L. Magna, A. Alberti, D. Ceratti, and D. Cahen, “Temperature-Dependent Optical band gap in CsPbBr 3 , MAPbBr 3 , and FAPbBr 3 Single Crystals,” J. Phys. Chem. Lett. 11, 2490 (2020). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 08 May, 2024 Read the published version in Applied Physics B → Version 1 posted Editorial decision: Revision requested 14 Mar, 2024 Reviews received at journal 25 Feb, 2024 Reviewers agreed at journal 23 Feb, 2024 Reviewers agreed at journal 17 Feb, 2024 Reviewers invited by journal 03 Feb, 2024 Editor assigned by journal 27 Jan, 2024 Submission checks completed at journal 18 Jan, 2024 First submitted to journal 17 Jan, 2024 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. 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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-3874292\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":false,\"archivedVersions\":[],\"articleType\":\"Research Article\",\"associatedPublications\":[],\"authors\":[{\"id\":267862002,\"identity\":\"5acd987f-65fa-48ea-93f6-caf24d86e98e\",\"order_by\":0,\"name\":\"XINZHI SUN\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"Jilin University\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"XINZHI\",\"middleName\":\"\",\"lastName\":\"SUN\",\"suffix\":\"\"},{\"id\":267862003,\"identity\":\"76092510-ac79-419f-9aff-c2f1c835fe39\",\"order_by\":1,\"name\":\"JIALIN BAI\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"Jilin University\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"JIALIN\",\"middleName\":\"\",\"lastName\":\"BAI\",\"suffix\":\"\"},{\"id\":267862004,\"identity\":\"217c51f9-9a4b-4ae2-ab98-d34834829d23\",\"order_by\":2,\"name\":\"TING WANG\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"Jilin Normal University\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"TING\",\"middleName\":\"\",\"lastName\":\"WANG\",\"suffix\":\"\"},{\"id\":267862005,\"identity\":\"5eacdf67-9c10-414e-8a1f-f9152fdce41d\",\"order_by\":3,\"name\":\"HANZHUANG ZHANG\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"Jilin University\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"HANZHUANG\",\"middleName\":\"\",\"lastName\":\"ZHANG\",\"suffix\":\"\"},{\"id\":267862006,\"identity\":\"9f53b289-eea2-4fa8-865c-6715fb7309cf\",\"order_by\":4,\"name\":\"WENYU JI\",\"email\":\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAArUlEQVRIiWNgGAWjYBACxmYg8YHHAsQ2IF4L4wweCRK0gAAzDwMpWpjbecykbWQkEhvYm7dJMNTcIcZhQC05PEAtPMfKJBiOPSNGC+82iBaJHDMJxobDRGqxAGmRf0OKFgawLTxEa+H/bNnDI2HcxpNWbJFwjAgthv3HEm/87LGR7Wc/vPHGhxpitDQwsEgw9jAwsIF4CYQ1MDDIA6PmA8MPYpSOglEwCkbBiAUATPsv331quWcAAAAASUVORK5CYII=\",\"orcid\":\"\",\"institution\":\"Jilin University\",\"correspondingAuthor\":true,\"prefix\":\"\",\"firstName\":\"WENYU\",\"middleName\":\"\",\"lastName\":\"JI\",\"suffix\":\"\"}],\"badges\":[],\"createdAt\":\"2024-01-18 01:44:10\",\"currentVersionCode\":1,\"declarations\":\"\",\"doi\":\"10.21203/rs.3.rs-3874292/v1\",\"doiUrl\":\"https://doi.org/10.21203/rs.3.rs-3874292/v1\",\"draftVersion\":[],\"editorialEvents\":[{\"content\":\"https://doi.org/10.1007/s00340-024-08222-z\",\"type\":\"published\",\"date\":\"2024-05-08T21:18:18+00:00\"}],\"editorialNote\":\"\",\"failedWorkflow\":false,\"files\":[{\"id\":49961989,\"identity\":\"026f0bb4-60de-4762-9ac0-6841096c0069\",\"added_by\":\"auto\",\"created_at\":\"2024-01-22 10:09:31\",\"extension\":\"png\",\"order_by\":1,\"title\":\"Figure 1\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":1023795,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eContact angle images of DMF drop on (a) s-ZnO and (b) s-ZnO:PEI films. SEM images of (c) s-ZnO and (d) s-ZnO:PEI films. AFM images of perovskite on (e) s-ZnO and (f) s-ZnO:PEI films.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"1.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-3874292/v1/a8176e2205744310feea8ac6.png\"},{\"id\":49961990,\"identity\":\"99737873-f1b7-4dc3-904f-0e2885d7f0d9\",\"added_by\":\"auto\",\"created_at\":\"2024-01-22 10:09:31\",\"extension\":\"png\",\"order_by\":2,\"title\":\"Figure 2\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":410318,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e(a) Absorption and PL spectra of the perovskite films on the two types of substrates. (b) XRD patterns of perovskite films. (c) PL decays of the perovskite films on different substrates. (d) The passivation of defects in s-ZnO films by PEI molecules.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"2.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-3874292/v1/1a5019206c0b8367c61b71d6.png\"},{\"id\":49961992,\"identity\":\"e46203f5-d686-47f6-bd62-c401a4927138\",\"added_by\":\"auto\",\"created_at\":\"2024-01-22 10:09:31\",\"extension\":\"png\",\"order_by\":3,\"title\":\"Figure 3\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":344330,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eXPS spectra of (a) the pristine s-ZnO O1s core-level peaks and (c) Zn 2p core-level peaks; XPS spectra of (b) the s-ZnO:PEI after introducing PEI O1s core-level peaks \\u0026nbsp;and (d) Zn 2p core-level peaks.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"3.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-3874292/v1/189994015eaffdcbbc1abda9.png\"},{\"id\":49961991,\"identity\":\"50830d8d-5c73-4352-bd3b-4b9646ffc22a\",\"added_by\":\"auto\",\"created_at\":\"2024-01-22 10:09:31\",\"extension\":\"png\",\"order_by\":4,\"title\":\"Figure 4\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":361521,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e(a) Schematic structure of the PeLED. (b) \\u003cem\\u003eJ−V−L\\u003c/em\\u003e, (c) current efficiency\\u003cem\\u003e−J−\\u003c/em\\u003e EQE, and (d) normalized EL spectra (at voltage of 5.0 V) of the PeLEDs with different ETLs. The photograph of s-ZnO:PEI device driving at voltage of 3.0 V is shown in the inset of (d).\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"4.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-3874292/v1/b31e8a46c3ffd5a2a5d2e757.png\"},{\"id\":56488375,\"identity\":\"9ffefab8-02ab-40a0-a622-d16b9d1cf4a2\",\"added_by\":\"auto\",\"created_at\":\"2024-05-14 21:32:07\",\"extension\":\"pdf\",\"order_by\":0,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"manuscript-pdf\",\"size\":3739155,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"manuscript.pdf\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-3874292/v1/3338420b-5be3-4c92-830f-6ad82c16ebe0.pdf\"}],\"financialInterests\":\"No competing interests reported.\",\"formattedTitle\":\"One-step fabricated ZnO electron-transporting layers for perovskite light-emitting diodes with sub-bandgap turn-on voltage\",\"fulltext\":[{\"header\":\"1. Introduction\",\"content\":\"\\u003cp\\u003eMetal halide perovskite light-emitting diodes (PeLEDs) have gained much attraction due to their unique photoelectrical properties such as high photoluminescence (PL) quantum yield [\\u003cspan citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e], excellent color purity [\\u003cspan citationid=\\\"CR2\\\" class=\\\"CitationRef\\\"\\u003e2\\u003c/span\\u003e], and low-cost solution processing [\\u003cspan citationid=\\\"CR3\\\" class=\\\"CitationRef\\\"\\u003e3\\u003c/span\\u003e]. Currently, the external quantum efficiency of the PeLEDs has exceeded 20% [\\u003cspan citationid=\\\"CR4\\\" class=\\\"CitationRef\\\"\\u003e4\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR5\\\" class=\\\"CitationRef\\\"\\u003e5\\u003c/span\\u003e], a theory limitation for conventional planar light-emitting diodes. However, the ion migration under high driving voltage remains a huge challenge to the stability of PeLEDs [\\u003cspan additionalcitationids=\\\"CR7\\\" citationid=\\\"CR6\\\" class=\\\"CitationRef\\\"\\u003e6\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e8\\u003c/span\\u003e], which could be mitigated by lowering the driving voltage through optimizing various functional layers.\\u003c/p\\u003e \\u003cp\\u003eRecently, PeLEDs turned on at sub-bandgap voltage have been reported by Liao \\u003cem\\u003eet al\\u003c/em\\u003e. [\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e]. Di \\u003cem\\u003eet al.\\u003c/em\\u003e proposed that the sub-bandgap electroluminescence (EL) turn-on behavior is attributed to the radiative recombination of non-thermal-equilibrium band-edge charge carriers [\\u003cspan citationid=\\\"CR10\\\" class=\\\"CitationRef\\\"\\u003e10\\u003c/span\\u003e]. In this scenario, the voltage losses at charge-transport layers and interfaces must be reduced as much as possible to achieve EL emission at ultralow driving voltages. Therefore, highly conductive (which means high carrier mobility or/and carrier density) and Ohmic contact available charge-transport/injection layers are indispensable. At the same time, it is crucial to prevent significant emission reduction caused by the charge-transport layers to achieve efficient light emission from the perovskite emitters.\\u003c/p\\u003e \\u003cp\\u003eMetal oxide films are promising charge-transport layers satisfying the above-mentioned requirements, which have been used as the electron- and hole-transport layers in organic LEDs, quantum-dot LEDs, and PeLEDs [\\u003cspan citationid=\\\"CR11\\\" class=\\\"CitationRef\\\"\\u003e11\\u003c/span\\u003e]. Amorphous ZnO films are very popular electron-transport layers (ETLs) due to their outstanding optoelectrical properties and resistance to the organic solvents used for depositing perovskite films [\\u003cspan additionalcitationids=\\\"CR13\\\" citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR14\\\" class=\\\"CitationRef\\\"\\u003e14\\u003c/span\\u003e]. Compared with the ETL obtained by the preformed ZnO nanoparticles, \\u003cem\\u003ein\\u003c/em\\u003e-\\u003cem\\u003esitu\\u003c/em\\u003e sol-gel ZnO (s-ZnO) films have more advantages, including low cost and accessibility for regulating their optoelectrical properties by adding additive into the precursor solution [\\u003cspan citationid=\\\"CR15\\\" class=\\\"CitationRef\\\"\\u003e15\\u003c/span\\u003e]. Although the ZnO films have excellent electrical properties, their quenching effect on the emission of perovskite emissive layers is harmful to the device performance, which is intensified by the defects on the ZnO surface. Therefore, surface modification for the ZnO films is essential to suppress these non-radiative processes of the perovskites. It has reported that this emission quenching effect is partially hindered by inserting an interlayer between ZnO and perovskite layer, such as polyethyleneimine (PEI) and its derivative polyethylenimine ethoxylated (PEIE) [\\u003cspan citationid=\\\"CR16\\\" class=\\\"CitationRef\\\"\\u003e16\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR17\\\" class=\\\"CitationRef\\\"\\u003e17\\u003c/span\\u003e]. However, the above-mentioned modification method typically requires two successive solution spin-coating processes, and damage to the underlying film by the upper-layer solution is inevitable. Besides, the device performance of PeLEDs, is rather sensitive to the thickness of these interlayers due to their insulation characteristics [\\u003cspan additionalcitationids=\\\"CR19\\\" citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR20\\\" class=\\\"CitationRef\\\"\\u003e20\\u003c/span\\u003e], These factors lead to poor reproducibility of well-performing devices.\\u003c/p\\u003e \\u003cp\\u003eIn this work, PeLEDs are fabricated by employing a s-ZnO:PEI film as the ETL to address the sensitivity of device repeatability to the forming factors of PEI or PEIE modifying layers. The PEI additive not only improves the wettability, but also passives defects of s-ZnO films (named as s-ZnO:PEI). This synergistic effect of PEI results in high-quality perovskite films on the s-ZnO:PEI ETL and suppresses emission quenching effect of the perovskite emitters. Consequently, a PeLED with the turn-on voltage as low as 1.9 V is obtained. Moreover, the peak current efficiency of the PeLED reaches 13.5 cd/A, 45% higher than that based on pristine s-ZnO ETL.\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e\"},{\"header\":\"2. Results and discussion\",\"content\":\"\\u003cp\\u003eIt is well known that the crystal quality of \\u003cem\\u003ein\\u003c/em\\u003e-\\u003cem\\u003esitu\\u003c/em\\u003e fabricated perovskite films is closely related to the surface properties of the target substrates. The wettability of the s-ZnO with and without PEI modifier is characterized and the results are shown in Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003ea, b. The contact angle for the DMF drop on s-ZnO:PEI film is smaller than that on the pristine s-ZnO film, which suggests the wettability of s-ZnO is improved with the introduction of PEI. Therefore, the s-ZnO:PEI films are more suitable for \\u003cem\\u003ein\\u003c/em\\u003e-\\u003cem\\u003esitu\\u003c/em\\u003e fabrication of perovskite films. The surface morphology of these ZnO films is evaluated in terms of scanning electron microscopy (SEM, acquired by scanning electron microscope, Regulus 8100) measurements. A completely covered and uniform s-ZnO film is obtained on the ITO substrate as can be observed from Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003ec. Moreover, the quality of the s-ZnO film is further improved by the doping of PEI in the ZnO precursor solution as shown in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003ed. The morphology properties of perovskite layers on different ZnO substrates are characterized by atomic force microscope (AFM, CoreAFM, nanosurf) measurements. The perovskite film deposited on the pristine s-ZnO layer is very uniform and smooth with root mean square (RMS) value of 1.48 nm (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003ee). In comparison, the surface roughness is reduced to 1.27 nm for the perovskite film deposited on the s-ZnO:PEI film (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003ef). The reduced surface roughness is conductive to limiting the leakage current across the devices.\\u003c/p\\u003e \\u003cp\\u003eFigure\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e shows the optical properties and crystal structure information of two perovskite films deposited on the s-ZnO and s-ZnO:PEI films. These two perovskite films display identical PL and absorption spectra as shown in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003ea, including emission/absorption peaks and profile, which mean that the perovskites share similar microstructure. The X-ray diffraction (XRD, measured by a R-AXIS-RAPID II) patterns shown in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003eb verify that these two perovskite films indeed possess the same crystal structure and particle size. The characteristic peaks of FAPbBr\\u003csub\\u003e3\\u003c/sub\\u003e films locate at 14.8\\u0026deg;, 21.2\\u0026deg;, 29.5\\u0026deg; and 33.4\\u0026deg;, corresponding to the (100), (110), (200) and (210) planes of cubic FAPbBr\\u003csub\\u003e3\\u003c/sub\\u003e crystal, respectively. These results imply that the PEI may have no influence on the perovskite growth. Nevertheless, the transient PL decays (measured through a HORIBA, IHR320) of these two perovskite films manifest that the perovskite deposited on the s-ZnO:PEI film possesses longer PL lifetime than that obtained on the pristine s-ZnO film, as shown in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003ec. This extension of PL lifetime is due to PEI passivating the defects in s-ZnO, inhibiting PL quenching of perovskite, rather than reducing the defects in perovskite, which will be confirmed below. The passivation mechanism of s-ZnO by PEI is shown in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003ed as further discussed below.\\u003c/p\\u003e \\u003cp\\u003eIn order to verify that PEI passivates the defects in s-ZnO, we measured the XPS (X-ray Photoelectron Spectroscopy, thermo scientific NEXSA) of s-ZnO and s-ZnO:PEI films. As shown in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ea, the O 1s core level spectra recorded from the pristine s-ZnO can be deconvoluted into three main subpeaks located at 530.1 eV, 531.4 eV and 532.0 eV, which can be attributed to Zn\\u0026ndash;O bonds, oxygen vacancies, and chemisorbed oxygen species such as hydroxyl (OH\\u003csup\\u003e\\u0026minus;\\u003c/sup\\u003e), respectively [\\u003cspan citationid=\\\"CR21\\\" class=\\\"CitationRef\\\"\\u003e21\\u003c/span\\u003e]. After adding PEI, the peak strength of 531.4 eV is significantly reduced as shown in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003eb, indicating that the defects are passivated. In addition, the binding energies of Zn 2p\\u003csub\\u003e1/2\\u003c/sub\\u003e and Zn 2p\\u003csub\\u003e3/2\\u003c/sub\\u003e in s-ZnO:PEI are 1045.4 eV and 1022.3 eV respectively, which is 0.6 eV higher than that of s-ZnO (1044.8 eV and 1021.7 eV, respectively) as shown in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ec, d. This should be caused by the interaction between PEI molecule and Zn ion.\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eTo verify the feasibility of s-ZnO as the ETL, PeLEDs are built by employing an inverted device structure consist of indium tin oxide (ITO) coated glass/ETL (~\\u0026thinsp;40 nm)/FAPbBr\\u003csub\\u003e3\\u003c/sub\\u003e (~\\u0026thinsp;50 nm)/poly [9-vinylcarbazole] (PVK, ~\\u0026thinsp;30 nm)/MoO\\u003csub\\u003e3\\u003c/sub\\u003e (~\\u0026thinsp;8 nm)/Al (~\\u0026thinsp;100 nm) as depicted in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ea. The s-ZnO and FAPbBr\\u003csub\\u003e3\\u003c/sub\\u003e films were fabricated according to previous reports [\\u003cspan citationid=\\\"CR15\\\" class=\\\"CitationRef\\\"\\u003e15\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR22\\\" class=\\\"CitationRef\\\"\\u003e22\\u003c/span\\u003e]. To fabricate s-ZnO:PEI ETL, the precursor of s-ZnO precursor solution is mixed with PEI (1 wt.% in DMF) according to volume ratio of 1:2. The PVK solution (8 mg/ml in CB) layers were spin-coated on the perovskite layer at 3000 rpm for 60 s in a glove box and then annealed at 80\\u0026deg;C for 15 min. Finally, these samples were transferred into a vacuum evaporation chamber jointed with the glove box to deposit the MoO\\u003csub\\u003e3\\u003c/sub\\u003e and Al layers under pressure of below 4\\u0026times;10\\u003csup\\u003e\\u0026minus;\\u0026thinsp;5\\u003c/sup\\u003e Pa. The photoelectric properties of PeLEDs were measured as described in our previous work [\\u003cspan citationid=\\\"CR23\\\" class=\\\"CitationRef\\\"\\u003e23\\u003c/span\\u003e].\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eFigure\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003eb shows the current density‒voltage‒luminance (\\u003cem\\u003eJ\\u003c/em\\u003e‒\\u003cem\\u003eV\\u003c/em\\u003e‒\\u003cem\\u003eL\\u003c/em\\u003e) curves of the PeLEDs based on s-ZnO and s-ZnO:PEI ETLs. These two \\u003cem\\u003eJ\\u003c/em\\u003e‒\\u003cem\\u003eV\\u003c/em\\u003e curves share similar profile, especially for the trap-filled limit voltage (\\u003cem\\u003eV\\u003c/em\\u003e\\u003csub\\u003eTFL\\u003c/sub\\u003e) [\\u003cspan citationid=\\\"CR24\\\" class=\\\"CitationRef\\\"\\u003e24\\u003c/span\\u003e], which implies that the density of traps (\\u003cem\\u003eN\\u003c/em\\u003e\\u003csub\\u003etrap\\u003c/sub\\u003e) in these two perovskite films is similar according to space-charge-limited current (SCLC) theory (\\u003cem\\u003eN\\u003c/em\\u003e\\u003csub\\u003etrap\\u003c/sub\\u003e=2\\u003cem\\u003eεε\\u003c/em\\u003e\\u003csub\\u003e0\\u003c/sub\\u003e\\u003cem\\u003eV\\u003c/em\\u003e\\u003csub\\u003eTFL\\u003c/sub\\u003e/\\u003cem\\u003eq\\u003c/em\\u003e\\u0026middot;\\u003cem\\u003eL\\u003c/em\\u003e\\u003csup\\u003e2\\u003c/sup\\u003e, \\u003cem\\u003eε\\u003c/em\\u003e\\u003csub\\u003e0\\u003c/sub\\u003e is vacuum permittivity and \\u003cem\\u003eε\\u003c/em\\u003e is the dielectric constant of the perovskite film, \\u003cem\\u003eq\\u003c/em\\u003e is the elementary charge, and \\u003cem\\u003eL\\u003c/em\\u003e is the thickness of perovskite film) [\\u003cspan citationid=\\\"CR25\\\" class=\\\"CitationRef\\\"\\u003e25\\u003c/span\\u003e]. These results further verify that the different PL lifetimes of perovskites deposited on s-ZnO and s-ZnO:PEI are due to the PL quenching effects induced by ZnO rather than the defects in perovskite films. However, the s-ZnO:PEI bases PeLED exhibits lower current densities than that of device with pristine s-ZnO as the ETL. This is attributed tothe insulating properties of the PEI and smoother perovskite films (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003ef). These two devices show the same turn-on voltage (defining the driving voltage when the device luminance is 0.1 cd/m\\u003csup\\u003e2\\u003c/sup\\u003e) and almost identical luminance within the whole driving voltage range. The same \\u003cem\\u003eV\\u003c/em\\u003e‒\\u003cem\\u003eL\\u003c/em\\u003e properties indicate that the PEI does not affect the electron injection capability of s-ZnO ETL. It worth noting that these two devices can be turned on at sub-bandgap voltage (1.9 V at 0.1 cd/m\\u003csup\\u003e2\\u003c/sup\\u003e, much lower than the optical bandgap of FAPbBr\\u003csub\\u003e3\\u003c/sub\\u003e divided by the elementary charge \\u003cem\\u003eq\\u003c/em\\u003e, ~\\u0026thinsp;2.3 V) as reported previously [\\u003cspan citationid=\\\"CR26\\\" class=\\\"CitationRef\\\"\\u003e26\\u003c/span\\u003e]. The radiative recombination of the non-thermal-equilibrium carriers induced by a small external bias is responsible to the sub-bandgap EL onset, rather than other high-order effect as reported recently [\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e].\\u003c/p\\u003e \\u003cp\\u003eDue to the similar of these two PeLEDs, s-ZnO:PEI based device possesses higher current efficiency of 13.5 cd/A, 45% higher than that of s-ZnO device (9.3 cd/A) as shown in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ec. The efficiency enhancement is attributed to the suppressed quenching effect due to the addition of PEI molecules. The EL spectra of these two devices are shown in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ed. Pure EL emissions completely from the perovskites without any contribution from adjacent layers confirms that the excitons are dominantly formed in the perovskite layers. The photograph shown in the inset of Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ed is the s-ZnO:PEI PeLED working at voltage of 3.0 V, which displays a vivid green emission. We attribute the enhanced device performance to the passivation effect of PEI to the defects of ZnO.\\u003c/p\\u003e\"},{\"header\":\"3. Conclusion\",\"content\":\"\\u003cp\\u003eIn summary, PeLED was prepared by using s-ZnO as ETL. Thanks to the improved wettability of s-ZnO films by the PEI modifier, high-quality FAPbBr\\u003csub\\u003e3\\u003c/sub\\u003e perovskite films were obtained with high coverage on the s-ZnO:PEI films. Moreover, the passivation of s-ZnO induced by the PEI molecules protects the perovsktie emitters from the quenching effect of defects in s-ZnO. Combining with the outstanding conductive properties of s-ZnO, excellent PeLEDs with low operation voltage are achieved. The peak current efficiency reaches 13.5 cd/A, and the driving voltage is 1.9 V at luminance of 0.1 cd/m\\u003csup\\u003e2\\u003c/sup\\u003e for the PEI-containing PeLEDs. The results of this study confirm the feasibility of s-ZnO as ETL for PeLED, and provide a reference and idea for preparing more efficient PeLED.\\u003c/p\\u003e\"},{\"header\":\"Declarations\",\"content\":\"\\u003cp\\u003e \\u003ch2\\u003eDisclosures.\\u003c/h2\\u003e \\u003cp\\u003eThe authors declare no conflicts of interest.\\u003c/p\\u003e \\u003c/p\\u003e\\u003ch2\\u003eFunding.\\u003c/h2\\u003e \\u003cp\\u003eThis work was supported by the program of the National Natural Science Foundation of China (Nos. 12374375, 12274173 and 12074148).\\u003c/p\\u003e\\u003ch2\\u003eAuthor Contribution\\u003c/h2\\u003e\\u003cp\\u003eAll authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by [XinZhi Sun], [JiaLin Bai], [Ting Wang], [HanZhuang Zhang] and [WenYu Ji] . The first draft of the manuscript was written by [XinZhi Sun] and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.\\u003c/p\\u003e\\u003ch2\\u003eData Availability.\\u003c/h2\\u003e \\u003cp\\u003eData underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.\\u003c/p\\u003e\"},{\"header\":\"References\",\"content\":\"\\u003col\\u003e\\u003cli\\u003e\\u003cspan\\u003eX. G. Wu, J. Tang, F. Jiang, X. Zhu, Y. Zhang, D. Han, L. Ling, and H. Zhong, \\u0026ldquo;Highly luminescent red emissive perovskite quantum dots-embedded composite films: Ligands capping and caesium doping-controlled crystallization process,\\u0026rdquo; Nanoscale. 11, 4942 (2019).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eH. Cho, J. S. Kim, C. Wolf, Y. H. Kim, H. J. Yun, S. H. Jeong, A. Sadhanala, V. Venugopalan, J. W. Choi, C. L. Lee, R. H. Friend, and T. W. Lee, \\u0026ldquo;High-Efficiency Polycrystalline Perovskite Light-Emitting Diodes Based on Mixed Cations,\\u0026rdquo; ACS Nano. 12, 2883 (2018).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eN. Wang, L. Cheng, R. Ge, S. Zhang, Y. Miao, W. Zou, C. Yi, Y. Sun, Y. Cao, R. Yang, Y. Wei, Q. Guo, Y. Ke, M. You, Y. Jin, Y. Liu, Q. Ding, D. Di, L. Yang, G. Xing, H. Tian, C. Jin, F. Gao, R. H. Friend, J. Wang, and W. Huang, \\u0026ldquo;Perovskite light-emitting diodes based on solution-processed self-organized multiple quantum wells,\\u0026rdquo; Nat. Photonics. 10, 699 (2016).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eY. Cao, N. Wang, H. Tian, J. Guo, Y. Wei, H. Chen, Y. Miao, W. Zuo, K. Pan, Y. He, H. Cao, Y. Ke, M. Xu, Y. Wang, M. Yang, K. Du, Z. Fu, D. Kong, D. Dai, Y. Jin, G. Li, H. Li, Q. Peng, J. Wang, and W. Huang, \\u0026ldquo;Perovskite light-emitting diodes based on spontaneously formed submicrometre-scale structures,\\u0026rdquo; Nature. 562, 249 (2018).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eK. Lin, J. Xing, L. N. Quan, F. P. G. Arquer, X. Gong, J. Lu, L. Xie, W. Zhao, D. Zhang, C. Yan, W. Li, X. Liu, Y. Lu, J. Kirman, E. H. Sargent, Q. Xiong, and Z. Wei, \\u0026ldquo;Perovskite light-emitting diodes with external quantum efficiency exceeding 20 per cent,\\u0026rdquo; Nature. 562, 245 (2018).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eN. Li, L. Song, Y. Jia, Y. Dong, F. Xie, L. Wang, S. Tao, and N. Zhao, \\u0026ldquo;Stabilizing Perovskite Light-Emitting Diodes by Incorporation of Binary Alkali Cations,\\u0026rdquo; Adv. Mater. 32, e1907786 (2020).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eL. Zhang, F. Yuan, J. Xi, B. Jiao, H. Dong, J. Li, and Z. Wu, \\u0026ldquo;Suppressing ion Migration Enables Stable Perovskite Light-Emitting Diodes with All-Inorganic Strategy,\\u0026rdquo; Adv. Funct. Mater. 30, 2001834 (2020).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eK. Anil. Y. Natalia, F. Yan, T. J. N. Hooper, P. J. S. Rana, F. Benny, P. C. Harikesh, S. Teddy, V. Parth, S. G. Mhaisalkar, and M. Nripan, \\u0026ldquo;Stabilizing the Electroluminescence of Halide Perovskites with Potassium Passivation,\\u0026rdquo; ACS. Energy. Lett. 5, 6, 1804\\u0026ndash;1813 (2020).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eS. Yuan, Q. W. Liu, Q. S. Tian, Y. Jin, Z. K. Wang, and L. S. Liao, \\u0026ldquo;Auger Effect Assisted Perovskite Electroluminescence Modulated by Interfacial Minority Carriers,\\u0026rdquo; Adv. Funct. Mater. 30, 1909222 (2020).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eY. Lian, D. Lan, S. Xing, B. Guo, Z. Ren, R. Lai, C. Zou, B. Zhao, R. H. Friend, and D. Di, \\u0026ldquo;Ultralow-voltage operation of light-emitting diodes,\\u0026rdquo; Nat. Commun. 13, 3845 (2022).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eC. Zang, S. Liu, M. Xu, R. Wang, C. Cao, Z. Zhu, J. Zhang, H. Wang, L. Zhang, W. Xie, and C. S. Lee, \\u0026ldquo;Top-emitting thermally activated delayed fluorescence organic light-emitting devices with weak light-matter coupling,\\u0026rdquo; Light Sci. Appl. 10, 116 (2021).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eY. C. Kim, S.-D. Baek, and J.-M. Myoung, \\u0026ldquo;Enhanced brightness of methylammonium lead tribromide perovskite microcrystal-based green light-emitting diodes by adding hydrophilic polyvinylpyrrolidone with oleic acid-modified ZnO quantum dot electron transporting layer,\\u0026rdquo; J. Alloys Compd. 786, 11 (2019).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eC. Tang, X. Shen, X. Wu, Y. Zhong, J. Hu, M. Lu, Z. Wu, Y. Zhang, W. W. Yu, and X. Bai, \\u0026ldquo;Optimizing the Performance of Perovskite Nanocrystal LEDs Utilizing Cobalt Doping on a ZnO Electron Transport Layer,\\u0026rdquo; J. Phys. Chem. Lett. 12, 10112 (2021).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eC.-J. Chang and S.-H. Yang, \\u0026ldquo;ZnO nanocrystals incorporating PEIE and a fluorene-based polyelectrolyte as electron transport layers for pure cesium-containing perovskite light-emitting devices,\\u0026rdquo; Mater. Res. Express. 6, 105304 (2019).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eY. Yuan, X. Xue, T. Wang, X. Chi, R. Wang, and W. Ji, \\u0026ldquo;Polyethylenimine modified sol-gel ZnO electron-transporting layers for quantum-dot light-emitting diodes,\\u0026rdquo; Org. Electron. 100, 106393 (2022).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eL. Meng, E. P. Yao, Z. Hong, H. Chen, P. Sun, Z. Yang, G. Li, and Y. Yang, \\u0026ldquo;Pure Formamidinium-Based Perovskite Light-Emitting Diodes with High Efficiency and Low Driving Voltage,\\u0026rdquo; Adv. Mater. 29, 1603826 (2017).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eY. Zhu, X. Zhao, B. Zhang, B. Yao, Z. Li, Y. Qu, and Z. Xie, \\u0026ldquo;Very efficient green light-emitting diodes based on polycrystalline CH(NH\\u003csub\\u003e3\\u003c/sub\\u003e)\\u003csub\\u003e2\\u003c/sub\\u003ePbBr\\u003csub\\u003e3\\u003c/sub\\u003e film achieved by regulating precursor concentration and employing novel anti-solvent,\\u0026rdquo; Org. Electron. 55, 35 (2018).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eV. Prakasam, F. Di Giacomo, R. Abbel, D. Tordera, M. Sessolo, G. Gelinck, and H. J. Bolink, \\u0026ldquo;Efficient Perovskite Light-Emitting Diodes: Effect of Composition, Morphology, And Transport Layers,\\u0026rdquo; ACS Appl. Mater. Interfaces. 10, 41586 (2018).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eL. Zhao, K. M. Lee, K. Roh, S. U. Z. Khan, and B. P. Rand, \\u0026ldquo;Improved Outcoupling Efficiency and Stability of Perovskite Light-Emitting Diodes using Thin Emitting Layers,\\u0026rdquo; Adv. Mater. 31, e1805836 (2019).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eY. J. Jung, S. Y. Cho, J. W. Jung, S. Y. Kim, and J. H. Lee, \\u0026ldquo;Influence of indium-tin-oxide and emitting-layer thicknesses on light outcoupling of perovskite light-emitting diodes,\\u0026rdquo; Nano Convergence. 6, 26 (2019).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eY. Lai, Z. Zeng, C. Liao, S. Cheng, J. Yu, Q. Zheng, and P. Lin, \\u0026ldquo;Ultralow switching current in HfO\\u003csub\\u003ex\\u003c/sub\\u003e/ZnO bilayer with tunable switching power enabled by plasma treatment,\\u0026rdquo; Appl. Phys. Lett. 109, 063501 (2016).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eD. Han, M. Imran, M. Zhang, S. Chang, X. G. Wu, X. Zhang, J. Tang, M. Wang, S. Ali, X. Li, G. Yu, J. Han, L. Wang, B. Zou, and H. Zhong, \\u0026ldquo;Efficient Light-Emitting Diodes Based on in Situ Fabricated FAPbBr\\u003csub\\u003e3\\u003c/sub\\u003e Nanocrystals: The Enhancing Role of the Ligand-Assisted Reprecipitation Process,\\u0026rdquo; ACS Nano. 12, 8808 (2018).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eZ. Liu, X. Xue, Z. Kang, R. Wang, H. Zhang, and W. Ji, \\u0026ldquo;Achieving high-performance in situ fabricated FAPbBr\\u003csub\\u003e3\\u003c/sub\\u003e and electroluminescence,\\u0026rdquo; Opt. Lett. 46, 4378 (2021).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eF. Cheng, R. He, S. Nie, C. Zhang, J. Yin, J. Li, N. Zheng, and B. Wu, \\u0026ldquo;Perovskite Quantum Dots as Multifunctional Interlayers in Perovskite Solar Cells with Dopant-free Organic Hole Transporting Layers,\\u0026rdquo; J. Am. Chem. Soc. 143, 5855 (2021).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eR. H. Bube, \\u0026ldquo;Trap Density Determination by Space-Charge-Limited Currents,\\u0026rdquo; J. Appl. Phys. 33, 1733 (1962).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eG. Mannino, I. Deretzis, E. Smecca, A. L. Magna, A. Alberti, D. Ceratti, and D. Cahen, \\u0026ldquo;Temperature-Dependent Optical band gap in CsPbBr\\u003csub\\u003e3\\u003c/sub\\u003e, MAPbBr\\u003csub\\u003e3\\u003c/sub\\u003e, and FAPbBr\\u003csub\\u003e3\\u003c/sub\\u003e Single Crystals,\\u0026rdquo; J. Phys. Chem. Lett. 11, 2490 (2020).\\u003c/span\\u003e\\u003c/li\\u003e\\u003c/ol\\u003e\"}],\"fulltextSource\":\"\",\"fullText\":\"\",\"funders\":[],\"hasAdminPriorityOnWorkflow\":false,\"hasManuscriptDocX\":true,\"hasOptedInToPreprint\":true,\"hasPassedJournalQc\":\"\",\"hasAnyPriority\":false,\"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\":\"info@researchsquare.com\",\"identity\":\"applied-physics-b\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":false,\"externalIdentity\":\"aphb\",\"sideBox\":\"Learn more about [Applied Physics B](http://link.springer.com/journal/340)\",\"snPcode\":\"340\",\"submissionUrl\":\"https://submission.nature.com/new-submission/340/3\",\"title\":\"Applied Physics B\",\"twitterHandle\":\"\",\"acdcEnabled\":true,\"dfaEnabled\":true,\"editorialSystem\":\"em\",\"reportingPortfolio\":\"Springer Hybrid\",\"inReviewEnabled\":true,\"inReviewRevisionsEnabled\":false},\"keywords\":\"\",\"lastPublishedDoi\":\"10.21203/rs.3.rs-3874292/v1\",\"lastPublishedDoiUrl\":\"https://doi.org/10.21203/rs.3.rs-3874292/v1\",\"license\":{\"name\":\"CC BY 4.0\",\"url\":\"https://creativecommons.org/licenses/by/4.0/\"},\"manuscriptAbstract\":\"\\u003cp\\u003eEfficient charge injection into the emitters, which can reduce the voltage loss at interfaces, is a prerequisite for high-performance light-emitting diodes, with low voltage operation. Here we develop a sol-gel ZnO (s-ZnO) electron-transport layer for the perovskite light-emitting diodes (PeLEDs) with green-emission formamidinium lead bromide (FAPbBr\\u003csub\\u003e3\\u003c/sub\\u003e) perovskites as emitters. Polyethylenimine (PEI) is mixed into the s-ZnO precursor as a modifier, which not only promotes the wettability of s-ZnO films, but also passivates the defects of s-ZnO without sacrificing their electrical conductivity. As a result, highly efficient FAPbBr\\u003csub\\u003e3\\u003c/sub\\u003e films are obtained on the s-ZnO films. The maximum current efficiency of PeLED with s-ZnO:PEI electron-transporting layer reaches 13.5 cd/A, 45% higher than that based on pristine s-ZnO without PEI modifier. Benefiting from the outstanding charge-transport properties of s-ZnO and high-quality perovskite film, the turn-on voltage of the s-ZnO based PeLEDs is only 1.9 V, much lower than the band-gap voltage (~\\u0026thinsp;2.3 V) of FAPbBr\\u003csub\\u003e3\\u003c/sub\\u003e.\\u003c/p\\u003e\",\"manuscriptTitle\":\"One-step fabricated ZnO electron-transporting layers for perovskite light-emitting diodes with sub-bandgap turn-on voltage\",\"msid\":\"\",\"msnumber\":\"\",\"nonDraftVersions\":[{\"code\":1,\"date\":\"2024-01-22 10:09:27\",\"doi\":\"10.21203/rs.3.rs-3874292/v1\",\"editorialEvents\":[{\"type\":\"communityComments\",\"content\":0},{\"type\":\"decision\",\"content\":\"Revision requested\",\"date\":\"2024-03-14T11:12:55+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"editorInvitedReview\",\"content\":\"\",\"date\":\"2024-02-26T02:16:08+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"reviewerAgreed\",\"content\":\"5e80ea8f-1c24-4304-9167-fef05aa78f2e\",\"date\":\"2024-02-23T11:50:06+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"reviewerAgreed\",\"content\":\"5275a9dd-3144-4cc7-b032-e1a197a73075\",\"date\":\"2024-02-17T09:56:18+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"reviewersInvited\",\"content\":\"\",\"date\":\"2024-02-03T12:32:19+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"editorAssigned\",\"content\":\"\",\"date\":\"2024-01-27T20:22:43+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"checksComplete\",\"content\":\"\",\"date\":\"2024-01-18T15:03:14+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"submitted\",\"content\":\"Applied Physics B\",\"date\":\"2024-01-18T01:34:19+00:00\",\"index\":\"\",\"fulltext\":\"\"}],\"status\":\"published\",\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"applied-physics-b\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":false,\"externalIdentity\":\"aphb\",\"sideBox\":\"Learn more about [Applied Physics B](http://link.springer.com/journal/340)\",\"snPcode\":\"340\",\"submissionUrl\":\"https://submission.nature.com/new-submission/340/3\",\"title\":\"Applied Physics B\",\"twitterHandle\":\"\",\"acdcEnabled\":true,\"dfaEnabled\":true,\"editorialSystem\":\"em\",\"reportingPortfolio\":\"Springer Hybrid\",\"inReviewEnabled\":true,\"inReviewRevisionsEnabled\":false}}],\"origin\":\"\",\"ownerIdentity\":\"4032551a-9a16-4cb9-8b19-89bbe8fd648c\",\"owner\":[],\"postedDate\":\"January 22nd, 2024\",\"published\":true,\"recentEditorialEvents\":[],\"rejectedJournal\":[],\"revision\":\"\",\"amendment\":\"\",\"status\":\"published-in-journal\",\"subjectAreas\":[],\"tags\":[],\"updatedAt\":\"2024-05-14T21:27:47+00:00\",\"versionOfRecord\":{\"articleIdentity\":\"rs-3874292\",\"link\":\"https://doi.org/10.1007/s00340-024-08222-z\",\"journal\":{\"identity\":\"applied-physics-b\",\"isVorOnly\":false,\"title\":\"Applied Physics B\"},\"publishedOn\":\"2024-05-08 21:18:18\",\"publishedOnDateReadable\":\"May 8th, 2024\"},\"versionCreatedAt\":\"2024-01-22 10:09:27\",\"video\":\"\",\"vorDoi\":\"10.1007/s00340-024-08222-z\",\"vorDoiUrl\":\"https://doi.org/10.1007/s00340-024-08222-z\",\"workflowStages\":[]},\"version\":\"v1\",\"identity\":\"rs-3874292\",\"journalConfig\":\"researchsquare\"},\"__N_SSP\":true},\"page\":\"/article/[identity]/[[...version]]\",\"query\":{\"redirect\":\"/article/rs-3874292\",\"identity\":\"rs-3874292\",\"version\":[\"v1\"]},\"buildId\":\"qtupq5eGEP_6zYnWcrvyt\",\"isFallback\":false,\"isExperimentalCompile\":false,\"dynamicIds\":[84888],\"gssp\":true,\"scriptLoader\":[]}","source_license":"CC-BY-4.0","license_restricted":false}