Formation of cubic perovskite alloy containing the ammonium cation of 2D perovskite for high performance solar cells with improved stability.

The perovskite solar cells have demonstrated to be strong competitors for conventional silicon solar cells due to their remarkable power conversion efficiency. However, their structural instability is the biggest obstacle to commercialization. To address these issues, we prepared (CHNH) (HC(NH)) PbI (CHNH = MA, HC(NH) = FA) perovskite alloys that contain ethylammonium (EA, CHCHNH ) and benzylammonium (BA, CHCHNH ) cations with no new additional two-dimensional (2D) perovskite phases. The crystal structures of alloy perovskites exhibit the cubic phase, which decreased the cation disorder and the intrinsic instability compared to 3D MAPbI perovskite. The band gaps of the alloy perovskites are almost the same as the corresponding 3D perovskites, which exhibit a high refractive index, a large absorption coefficient, and paramagnetic properties for the production of high performance photovoltaic devices. After we constructed the solar cell with the configuration of regular (n-i-p) solar cells using the alloy perovskites, the power conversion efficiencies (PCE) of the MAEAPbI perovskite solar cell showed the highest efficiency, which was 10.22%, under 1 sun illumination.