Elucidation of Charge Recombination and Accumulation Mechanism in Mixed Perovskite Solar Cells

Organic-inorganic perovskite solar cells (PSCs) have gained considerable attention owing to their impressive photovoltaic properties and simple device manufacturing. In general, PSC employs a perovskite absorber material sandwiched between an electron and hole selective transport layer optimized with respect to optimal band alignment, efficient charge collection, and low interfacial recombination. The interfaces between the perovskite absorber and respective selective contacts play a crucial role in determining photovoltaic performance and stability of PSCs. However, a fundamental understanding is lacking, and there is poor understanding in controlling the physical processes at the interfaces. Herein, we investigate the interfacial characteristics of PSCs with both planar and mesoporous architecture that provide a deeper insight into the charge recombination and accumulation mechanism and the origin of open-circuit voltage (V-oc). The effect of electron-and hole-selective contacts in the final cell performance of PSCs has been analyzed by impedance spectroscopy and capacitance-frequency analysis. This study demonstrates that the excess of charge accumulation under illumination in planar-based devices is responsible for the origin of V-oc and hysteresis phenomena.