Efficient wide band gap double cation – double halide perovskite solar cells

Abstract

In this work we study the band gap variation and properties of the perovskite compound Cs_0.15FA_0.85Pb(Br_xI_1−x)₃ as a function of the halide composition, with the aim of developing an efficient complementary absorber for MAPbI₃ in all-perovskite tandem devices. We have found the perovskite stoichiometry Cs_0.15FA_0.85Pb(Br_0.7I_0.3)₃ to be a promising candidate, thanks to its band gap of approximately 2 eV. Single junction devices using this perovskite absorber lead to a maximum PCE of 11.5%, among the highest reported for solar cells using perovskites with a band gap wider than 1.8 eV.