Abstract
Metal halide perovskites have received considerable attention in the field of electroluminescence, and the external quantum efficiency of perovskite light-emitting diodes has exceeded 20%. CH3NH3PbBr3 has been intensely investigated as an emitting layer in perovskite light-emitting diodes. However, perovskite films comprising CH3NH3PbBr3 often exhibit low surface coverage and poor crystallinity, leading to high current leakage, severe nonradiative recombination, and limited device performance. Herein, we demonstrate a rationale for composition engineering to obtain high-quality perovskite films. We first reduce pinholes by adding excess CH3NH3Br to the actual CH3NH3PbBr3 films, and we then add CsBr to improve the crystalline quality and to passivate nonradiative defects. As a result, the (CH3NH3)1−xCsxPbBr3 based perovskite light-emitting diodes exhibit significantly improved external quantum and power efficiencies of 6.97% and 25.18 lm/W, respectively, representing an improvement in performance dozens of times greater than that of pristine CH3NH3PbBr3-based perovskite light-emitting diodes. Our study demonstrates that composition engineering is an effective strategy for enhancing the device performance of perovskite light-emitting diodes.

Keywords: perovskite, light-emitting diode (LED), composition engineering, ion doping
Acknowledgements
The work was financially supported by the National Natural Science Foundation of China (Grant Nos. 51802102, 21805101, and 51902110), Natural Science Foundation of Fujian Province (No. 2019J01057), Promotion Program for Young and Middle-aged Teacher in Science and Technology Research of Huaqiao University (No. ZQN-PY607), and Scientific Research Funds of Huaqiao University (Nos. 16BS201, 17BS409, and 19BS105).
Footnotes
Chuanzhong Yan received his B.E. degree in 2019 from College of Materials Science and Engineering, Huaqiao University, China. He is a Master’s candidate in Prof. Zhanhua Wei’s group at Institute of Luminescent Materials and Engineering, College of Materials Science and Engineering, Huaqiao University, China. His current research focuses on perovskite light-emitting diodes.
Kebin Lin is a Ph.D. candidate in Prof. Zhanhua Wei’s group at Institute of Luminescent Materials and Engineering, College of Materials Science and Engineering, Huaqiao University, China. He received his B.E. degree in 2016 from College of Materials and Chemical Engineering, Zhongyuan University of Technology, China. His research interests include perovskite light-emitting diodes and perovskite solar cells.
Jianxun Lu is a Ph.D. candidate in Prof. Zhanhua Wei’s group at Institute of Luminescent Materials and Engineering, College of Materials Science and Engineering, Huaqiao University, China. He received his B.E. degree from College of Materials Science and Engineering, Huaqiao University, China in 2017. His research interests include perovskite light-emitting diodes and perovskite solar cells.
Zhanhua Wei is a full professor at Institute of Luminescent Materials and Engineering, College of Materials Science and Engineering, Huaqiao University, China. He received his B.S. degree in 2011 from Department of Chemistry, Xiamen University, China and Ph.D. degree in 2015 from Prof. Shihe Yang’s group, Department of Chemistry, The Hong Kong University of Science and Technology, China. His current research focuses on the synthesis of perovskite materials, perovskite light-emitting diodes, perovskite solar cells, and other optoelectronic devices.
These authors contributed equally to this work.
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