Defect Passivation on Lead‐Free CsSnI3 Perovskite Nanowires Enables High‐Performance Photodetectors with Ultra‐High Stability.pdf
Vol.:(0123456789) 1 3 Defect Passivation on Lead‑Free ­CsSnI3  Perovskite Nanowires Enables High‑Performance  Photodetectors with Ultra‑High Stability Zheng Gao1,2,3, Hai Zhou1 *, Kailian Dong2, Chen Wang2, Jiayun Wei3, Zhe Li2,  Jiashuai Li2, Yongjie Liu2, Jiang Zhao3 *, Guojia Fang2 * HIGHLIGHTS •	 Through materials analysis and theoretical calculations, the defects of ­CsSnI3 nanowires (NWs) were effectively passivated via incor- porating 1-butyl-2,3-dimethylimidazolium chloride into perovskites. •	 The high-performance ­CsSnI3 NW photodetectors (PDs) were achieved with a responsivity of up to 0.237 A ­W−1, a high detectivity  of 1.18 × ­1012 Jones and a linear dynamic range of 180 dB. These values are comparable to the reported high-performance Pb-based  perovskite PDs and higher than those of the Pb-free perovskite PDs. •	 Our unpackaged devices exhibit ultra-high stability with no degradation after 60 days of storage in air (25 °C, 50% humidity). ABSTRACT  In recent years, Pb-free ­CsSnI3 perovskite materials with excel- lent photoelectric properties as well as low toxicity are attracting much atten- tion in photoelectric devices. However, deep level defects in ­CsSnI3, such as  high density of tin vacancies, structural deformation of ­SnI6 − octahedra and  oxidation of ­Sn2+ states, are the major challenge to achieve high-performance  ­CsSnI3-based photoelectric devices with good stability. In this work, defect pas- sivation method is adopted to solve the above issues, and the ultra-stable and  high-performance ­CsSnI3 nanowires (NWs) photodetectors (PDs) are fabricated  via incorporating 1-butyl-2,3-dimethylimidazolium chloride salt (BMIMCl) into  perovskites. Through materials analysis and theoretical calculations, ­BMIM+  ions can effectively passivate the Sn-related defects and reduce the dark cur- rent of ­CsSnI3 NW PDs. To further reduce the dark current of the devices, the  polymethyl methacrylate is introduced, and finally, the dual passivated ­CsSnI3  NWPDs show ultra-high performance with an ultra-low dark current of 2 × ­10–11  A, a responsivity of up to 0.237 A ­W−1, a high detectivity of 1.18 × ­1012 Jones and a linear dynamic range of 180 dB. Furthermore, the  unpackaged devices exhibit ultra-high stability in device performance after 60 days of storage in air (25 °C, 50% humidity), with the  device performance remaining above 90%. KEYWORDS  Pb-free; Perovskite; CsSnI3; Photodetector; Nanowire   e-ISSN 2150-5551       CN 31-2103/TB ARTICLE Cite as Nano-Micro Lett.  (2022) 14:215 Received: 11 September 2022  Accepted: 18 October 2022  Published online: 7 November 2022  © The Author(s) 2022 https://doi.org/10.1007/s40820-022-00964-9  *	 Hai Zhou, hizhou@dgut.edu.cn; Jiang Zhao, zhaojiang@hubu.edu.cn; Guojia Fang, gjfang@whu.edu.cn 1	 International School of Microelectronics, Dongguan University of Technology, Dongguan 523808, Guangdong, People’s Republic of China 2	 Key Lab of Artificial Micro‑ and Nano‑Structures of Ministry of Education of China, School of Physics and Technology, Wuhan University,  Wuhan 430072, People’s Republic of China 3	 Faculty of Physics and Electronic Science, Hubei University, Wuhan 430062, People’s Republic of China 	 Nano-Micro Lett. (2022) 14:215 215  Page 2 of 10 https://doi.org/10.1007/s40820-022-00964-9 © The authors 1  Introduction Because of excellent photoelectronic properties and low  fabrication cost, organic–inorganic hybrid perovskites have  become a hot topic in recent years and are widely used in  solar cells [1–4], photodetectors (PDs) [5–7], light-emitting  diodes (LEDs) [8, 9], etc. Until now, the highest certified  power conversion efficiency of perovskite solar cells has  exceeded 25% [10, 12], and the LEDs based on lead-con- taining perovskite materials also show high performance; for  example, the highest external quantum efficiency of green  LEDs has exceeded 20% [13–15]. However, the presence of  heavy metal lead severely limits the commercialization of  lead halide materials, which will face security risks of heavy  metal lead leakage during mass production, transportation,  installation and operation. In this context, lead-free perovskite materials based on  tin (Sn) [14], bismuth [15], germanium [16], antimony [17]  or copper [18] have attracted much attention. Among these  lead-free perovskite materials, ­CsSnI3 is more popular in  photovoltaic applications due to its similar crystal and elec- tronic structure to its Pb-based counterpart. Besides, inor- ganic perovskite ­CsSnI3 has a narrow optical band gap close  to the Shockley–Queisser limit, with long lifetime and high  charge carrier mobility [19, 20]. Moreover, the melting point  of the ­CsSnI3 is up to 451 °C, which means that it has excel- lent inherent thermal stability. Therefore, the development  of the inorganic perovskite ­CsSnI3 shows great prospect, and  many scientists have achieved meaningful results [21–23].  Jin et al. [24] reported the growth of ­CsSnX3 (X = Br, I) per- ovskite semiconductors with controlled orientation and size  by high-temperature vapor-phase epitaxy on mica sheets.  Yang et al. [25] reported the preparation of ­CsSnX3 (X = Cl,  Br, and I) perovskite nanowire (NW) arrays by chemical  vapor deposition with a responsivity of 54 mA ­W−1, a  detectivity of 3.85 × ­10–5 Jones, and fast rise and decay time  constants of 83.8 and 243.4 ms, respectively. However, the  efficiency of the solution-processed ­CsSnI3 devices was  much lower than that of the Pb-based analogs, mainly due  to the weak Sn-I bond of inorganic ­CsSnI3, which causes  lower tin vacancy formation energy and the easy oxidation  of ­Sn2+ to ­Sn4+, leading to a high level of self-P doping in  inorganic ­CsSnI3 perovskites, and the reduction in the device  performance and the decrease in the output stability [26].  Therefore, strategies to passivate the Sn defects in inorganic  ­CsSnI3 perovskites while maintaining their environmental  stability are urgently needed. In this work, 1-butyl-2,3-dimethylimidazolium chloride  (BMIMCl) salt is introduced to passivate the defects of per- ovskite ­CsSnI3 NWs. Through materials analysis and theo- retical calculations, the BMIMCl has a strong passivating  effect on Sn-related defects via large π-bonds in N–C = N,  and the lone pair of electrons in large π-bonds enhances the  electron density around ­Sn2+ in ­CsSnI3 and protects it from  oxidation to ­Sn4+; thus, the fabricated ­CsSnI3 NWs with  BMIMCl show high light absorption, low defect density  and air stability. To further reduce the dark current of the  devices, the polymethyl methacrylate (PMMA) was applied,  and finally, the dual passivated ­CsSnI3 NW PDs show ultra- high performance with an ultra-low dark current of 2 × ­10–11  A, a high responsivity of 0.237 A ­W−1, a high detectivity  of 1.18 × ­1012 Jones and a linear dynamic range (LDR) of  180 dB. Besides, our unpackaged devices exhibit good sta- bility with less than 10% degradation in device performance  after 60 days of storage in air (25 °C, 50% humidity), dem- onstrating good application potential. 2  Experimental and Calculation 2.1  Device Fabrication A pre-etched indium-tin oxide (ITO) glass substrate was  ultrasonically cleaned with detergent, deionized water,  ethanol and iso-propyl alcohol for 15 min, respectively. To  prepare the ­SnO2 precursor solution, the ­SnO2 stock solu- tion (1 mL) was diluted in deionized water (4 mL). The as- cleaned ITO substrate was treated with UV ozone at 100 °C  for 10 min. A compact layer of ­SnO2 was spin-coated on top  of the ITO at 4000 rpm for 30 s. Then, it was heated at 150  °C for 30 min in air. After that, the samples were treated  with UV ozone for 10 min. Subsequently, the samples were  transferred into a ­N2 filled glovebox with ­H2O and ­O2 con- centrations of < 0.1 ppm. A layer of ­PbI2 film was fabri- cated by spin-coating ­PbI2/BMIMCl (1 mol ­mL−1/0, 5, 8,  10 and 15 mg ­mL−1) in DMF at 3000 rpm for 30 s, followed  by annealing at 70 °C for 10 min. Then, the substrate was  soaked in the prepared CsI/SnI2/SnF2 (5 /4 /0.4 mg ­mL−1)  solution in anhydrous methanol for 2 h. After that, the sub- strates were placed in an isopropyl alcohol solution for 20 s  and then annealed at 180 °C for 10 min. Finally, a layer of  	 Nano-Micro Lett. (2022) 14:215 215  Page 8 of 10 https://doi.org/10.1007/s40820-022-00964-9 © The authors that the introduction of the BMIMCl and PMMA not only  enhances the optoelectronic performance of the device, but  also improves the stability of the device. 4  Conclusions In conclusion, the BMIMCl was introduced in ­CsSnI3  NWs to passivate the Sn vacancies and reduce the dark  current of the ­CsSnI3 NWPDs. Experimental analysis and  theoretical calculation demonstrate that ­BMIM+ ions can  effectively suppress the oxidation of ­Sn2+ to ­Sn4+ in the  BMIMCl + ­CsSnI3 sample. For further reduce the dark cur- rent of the devices, the PMMA was applied, and finally,  the dual passivated ­CsSnI3 NW PDs show ultra-high per- formance with an ultra-low dark current of 2 × ­10–11 A, a  responsivity of up to 0.237 A ­W−1, a high detectivity of  1.18 × ­1012 Jones and a linear dynamic range of 180 dB. Fur- thermore, our unpackaged devices exhibit ultra-high stabil- ity in device performance after 60 days of storage in air  (25 °C, 50% humidity), with the device performance remain- ing above 90%. This work provides a simple and effective  method for the preparation of high-performance, highly sta- ble Pb-free perovskite photoelectric devices. Acknowledgements  We acknowledge grants from the National  Natural Science Foundation of China (Nos. 51972101, 62074117,  12134010) and the Shenzhen Fundamental Research Program (No.  JCYJ20190808152609307). Funding  Open access funding provided by Shanghai Jiao Tong  University. Open Access  This article is licensed under a Creative Commons  Attribution 4.0 International License, which permits use, sharing,  adaptation, distribution and reproduction in any medium or format,  as long as you give appropriate credit to the original author(s) and  the source, provide a link to the Creative Commons licence, and  indicate if changes were made. The images or other third party  material in this article are included in the article’s Creative Com- mons licence, unless indicated otherwise in a credit line to the  material. If material is not included in the article’s Creative Com- mons licence and your intended use is not permitted by statutory  regulation or exceeds the permitted use, you will need to obtain  permission directly from the copyright holder. To view a copy of  this licence, visit http://​creat​iveco​mmons.​org/​licen​ses/​by/4.​0/. Supplementary Information  The online version contains  supplementary material available at https://​doi.​org/​10.​1007/​ s40820-​022-​00964-9. References 	1.	 P. Guo, H. Zhu, W. Zhao, C. Liu, L. Zhu et al., Interfacial  embedding of laser-manufactured fluorinated gold clusters  enabling stable perovskite solar cells with efficiency over 24%.  Adv. Mater. 33(36), 2101590 (2021). https://​doi.​org/​10.​1002/​ adma.​20210​1590 	2.	 Y. Zhang, Y. Ma, Y. Wang, X. Zhang, C. Zuo et al., Lead-free  perovskite photodetectors: progress, challenges, and opportu- nities. Adv. Mater. 33(26), 2006691 (2021). https://​doi.​org/​10.​ 1002/​adma.​20200​6691 	3.	 B.B. Yu, Z. 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Title: Defect Passivation on Lead‑Free CsSnI3 Perovskite Nanowires Enables High‑Performance Photodetectors with Ultra‑High Stability ​
Authors:  Zheng Gao, Hai Zhou, Kailian Dong, Chen Wang, Jiayun Wei, Zhe Li, Jiashuai Li, Yongjie Liu, Jiang Zhao, Guojia Fang ​
Publisher: Nano-Micro Letters ​
Date: 7 November 2022 ​
Abstract: In recent years, Pb-free CsSnI3 perovskite materials with excellent photoelectric properties as well as low toxicity are attracting much attention in photoelectric devices. ​ However, deep level defects in CsSnI3, such as high density of tin vacancies, structural deformation of SnI6 − octahedra and oxidation of Sn2+ states, are the major challenge to achieve high-performance CsSnI3-based photoelectric devices with good stability. ​ In this work, defect passivation method is adopted to solve the above issues, and the ultra-stable and high-performance CsSnI3 nanowires (NWs) photodetectors (PDs) are fabricated via incorporating 1-butyl-2,3-dimethylimidazolium chloride salt (BMIMCl) into perovskites. ​ Through materials analysis and theoretical calculations, BMIM+ ions can effectively passivate the Sn-related defects and reduce the dark current of CsSnI3 NW PDs. ​ To further reduce the dark current of the devices, the polymethyl methacrylate is introduced, and finally, the dual passivated CsSnI3 NWPDs show ultra-high performance with an ultra-low dark current of 2 ×10–11 A, a responsivity of up to 0.237 A W−1, a high detectivity of 1.18×1012 Jones and a linear dynamic range of 180 dB. ​ Furthermore, the unpackaged devices exhibit ultra-high stability in device performance after 60 days of storage in air (25 °C, 50% humidity), with the device performance remaining above 90%. ​ 