LAUSR

Abstract Recently, the mixed-cation perovskites have been widely used in high-performance perovskite solar cells due to its excellent photoelectric properties. However, the mixed precursor-based method, particularly the complicated composition engineering, will cause phase transitional strain, low phase crystallinity and phase instability. Hence, interface modification engineering is very necessary to improve the phase crystallinity and stability, and then to optimize the performance of the photovoltaic devices. Herein, an interfacial engineering strategy is developed to enlarge the grain size and enhance the crystallinity of perovskite film through inserting a methylammonium chloride (MACl) layer between the SnO2 electron transport layer and perovskite layer. Therefore, the carrier extraction and transport are accelerated and the interfacial recombination is suppressed. Consequently, the optimal MACl-modified devices achieve a very high open circuit voltage of 1.19 V and a power conversion efficiency of 19.20% with the negligible hysteresis and enhanced stability in ambient condition, showing great superiority to the control devices without any modification.