[11a-M111-1~10] 12.1 Fabrications and Structure Controls

[11a-M111-1] Mixed 3D–2D Passivation Treatment for Mixed-Cation Lead Mixed-Halide Perovskite Solar Cells for Higher Efficiency and Better Stability

〇(D)YONGYOON CHO¹, Arman Mahboubi Soufiani¹, Jae Sung Yun¹, Jincheol Kim¹, Da Seul Lee¹, Jan Seidel², Xiaofan Deng¹, Martin A. Green¹, Shujuan Huang¹, Anita W.Y. Ho-Baillie¹ (1.UNSW SPREE, 2.UNSW school of mat. sci. and eng.)

Keywords:perovskite solar cell, 2D perovskite, passivation

Layered low-dimensional perovskite structures employing bulky organic ammonium cations have shown significant improvement on stability but poorer performance generally compared to their three-dimensional (3D) counterparts. In this study, we report on a mixed passivation (MP) treatment that uses a mixture of bulky organic ammonium iodide (iso-butylammonium iodide, iBAI) and formammidinium iodide (FAI), enhancing both power conversion efficiency and stability. Through a combination of inactivation of the interfacial trap sites, characterized by photoluminescence measurement, and potential formation of an interfacial energetic barrier by which ionic transport is reduced, demonstrated by Kelvin probe force microscopy, MP treatment of the perovskite/hole transport layer interface significantly suppresses photo-current hysteresis. Using this MP treatment, our champion mixed halide perovskite cell achieved a reverse scan and stabilized power conversion efficiency of 21.7%. Without encapsulation, the devices showed excellent moisture-stability, sustaining over 87% of the original performance after 38 days storage in ambient environment under 75 ±20% relative humidity. This work shows that FAI/iBAI, is a new and promising material combination for passivating perovskite/selective-contact interfaces.