The Formation of Homogenous FAPbI3‒CsSnI3 Alloys for Efficient, Ideal-Bandgap Perovskite Solar Cells

The alloying behavior between FAPbI3 and CsSnI3 perovskites is carefully studied for the first time, which has led to the realization of single-phase hybrid perovskites of (FAPbI3)1-x(CsSnI3)x (0perovskites exhibit stable, homogenous composition/microstructure at nanoscale as confirmed by microscopic characterization. The ideal bandgap of 1.3 eV for single-junction solar cell operation is achieved in the rationally-designed (FAPbI3)0.7(CsSnI3)0.3-composition perovskite. Solar cells based on this new perovskite show power conversion efficiency up to 14.6%.