Application of mixed-organic-cation for high performance hole-conductor-free perovskite solar cells.

ABX-type organic lead halide perovskites have gained increasing attention as light harvester for solar cells due to their high power conversion efficiency (PCE). Recently, it has become a trend to avoid the use of expensive hole-transport materials (HTMs) and precious metals, such as Au, to be competitive in future commercial development. In this study, we fabricated mixed-cation perovskite-based solar cells through one-step spin-coating using methylammonium (CHNH) and formamidinium (HN=CHNH) cations to extend the optical absorption range into the red region and enhance the utilization of solar light.