Abstract
It is necessary to evaluate the interactions between the different functional layers in optoelectronic devices to optimize device performance. Recently, the I-rich all-inorganic perovskite CsPbI2Br has attracted tremendous attention for use in solar cell applications because of its suitable band gap and favorable photo and thermal stabilities. It has been reported that the undesirable phase degradation of the photoactive a phase CsPbI2Br to the non-perovskite δ phase could be triggered by high humidity. To obtain stable devices, it is thus important to protect CsPbI2Br from moisture. In this paper, CuI, a non-hygroscopic p-type hole-transporting material, is found to induce the phase degradation of α-CsPbI2Br to the δ-CsPbI2Br. The rate and extent of phase degradation of CsPbI2Br are closely associated with the heating temperature and coverage of a CuI granular capping layer. This discovery is different from the widely reported water-induced phase degradation of CsPbI2Br. Our work highlights the importance of careful selection of hole-transporting materials during the processing of I-rich all-inorganic CsPbX3 (X=Br, I) perovskites to realize high-performance optoelectronic devices.
摘要
由于具有良好的光吸收特性和光热稳定性, 富碘型全无机钙钛矿结构CsPbI2Br光电功能材料受到了广泛关注. 然而, 具有钙钛矿结构的α相CsPbI2Br在高湿度环境下易发生相变, 转变为具有非钙钛矿结构的δ相CsPbI2Br. 因此基于CsPbI2Br材料的光电器件通常需要在干燥环境中保存以维持器件性能稳定. 在本研究中, 我们将干燥且不吸湿的p型无机空穴传输材料CuI的颗粒涂覆在α相CsPbI2Br薄膜表面并对样品进行加热, 实验测试结果表明, 这层CuI颗粒同样会诱发α相CsPbI2Br转变为δ相CsPbI2Br, 且该相变过程的速率随加热温度的升高、CuI颗粒覆盖度的提升而加快. 这种异于湿度诱导的钙钛矿结构CsPbI2Br相变行为, 为研究者在思考、评估和分析基于富碘型全无机钙钛矿结构CsPbX3 (X=Br, I)光电功能材料的高性能光电器件稳定性问题上, 提供了有益的借鉴和帮助.
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Acknowledgements
This work was supported primarily by the National Key Research and Development Program of China (2018YFA0209303), the National Natural Science Foundation of China (U1663228, 51902153, 51972165 and 61377051), and the Fundamental Research Funds for the Central Universities of China. We thank Prof. Wang X, Feng S, Huang H and Meng Q at the School of Physics, Nanjing University for informative discussions as well as experimental and technical assistance.
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Zhu Z conducted the experiments and wrote the paper. Yu T, Zhu Z, Feng J, and Li J conceived the experiments, analyzed the results, and revised the paper. Su W, Han X, Li Z, and Zou Z helped with sample preparation and characterization. All authors contributed to the general discussion.
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Zhi Zhu is a PhD student at the School of Physics, Nanjing University. He received his BSc degree from Wuhan University in 2017. His current research interest focuses on all-inorganic perovskites and hole-transporting materials in perovskite solar cells.
Tao Yu is a professor of physics at Nanjing University and Senior Scientist at the National Laboratory of Solid State Microstructures. He received his BSc and MSc degrees from Wuhan University in 1990 and 1993, respectively, and his PhD from Nanjing University in 1997. He worked as a visiting scholar & participating guest researcher in Prof. Yuen-Ron Shen’s group at Lawrence Berkeley National Laboratory, UC Berkeley, USA, as part of the Berkeley Scholars’ Program in 2002–2004. His research is focused on advanced functional micro/nanostructured materials that display photoelectric transformations as well as their solar photon conversion applications in the fields of clean and renewable energy.
Zhigang Zou received his PhD from the University of Tokyo, Japan, in 1996, and then he became a researcher at the Photoreaction Control Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Japan. He has been with Nanjing University as a distinguished Professor of the Chang Jiang Scholars Program since 2003. He was elected as an academician of the Chinese Academy of Sciences in 2015. He is a director of Jiangsu Key Laboratory for Nano Technology, Nanjing University. His current research interests are photocatalysis, solar cells, and fuel cells.
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Zhu, Z., Su, W., Feng, J. et al. Phase degradation of all-inorganic perovskite CsPbI2Br films induced by a p-type CuI granular capping layer. Sci. China Mater. 63, 2487–2496 (2020). https://doi.org/10.1007/s40843-020-1462-4
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DOI: https://doi.org/10.1007/s40843-020-1462-4