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Air-processed, large grain perovskite films with low trap density from perovskite crystal engineering for high-performance perovskite solar cells with improved ambient stability

Ding, Manman, Sun, Leijie, Chen, Xiayan, Luo, Tianyuan, Ye, Tian, Zhao, Chunyan, Zhang, Wenfeng, Chang, Haixin
Journal of materials science 2019 v.54 no.18 pp. 12000-12011
air, encapsulation, engineering, mixing, relative humidity, solar cells
High-performance perovskite solar cell processed in ambient air is a big challenge due to the sensitivity of perovskite films to air. Many defects are generated easily at grain boundaries and in the perovskite films by conventional molecular/ion precursor solution mixing methods (i.e., solution mixing-based method), which restrict its stability in air and photovoltaic performance with most power conversion efficiency less than 15%. In this work, we develop a facile method for air-processed, highly crystalline, quasi-3D perovskite film with large grain size (over 6.6 times bigger than that from control conventional method) and improved ambient air stability by phenylethylammonium (PEA)-doped MA₁₋ₓPEAₓPbI₃ perovskite crystal engineering. Furthermore, benefiting from PEA⁺ doping and crystal engineering, the trap density decreases 50% compared with control. Consequently, with the optimal concentration of PEA doping, the power conversion efficiency increases from 15.6% for conventional solution mixing-based perovskite solar cells to 17.6% for crystal engineering-based ones with significantly improved moisture stability. The perovskite crystal engineering-based solar cells without any encapsulation retain 75% of the initial performance after 30-day storage in ambient air under a relative humidity of 50 ± 10%, and two times faster degradation rate is observed for control, conventional solution mixing-based perovskite solar cells when compared with crystal engineering-based ones.