Compositional Investigation for Bandgap Engineering of Wide Bandgap Triple Cation Perovskite

Perovskite solar cells have shown their potential for multijunction applications due to their tunable bandgap. This research focuses on triple cation (3C) wide bandgap perovskites ranging from 1.6 to 1.76 eV, an ideal bandgap choice for 2-terminal tandems. The bandgap is changed via the X-site substitution of iodine (I) with bromine (Br) and via cation substitution, with various concentrations of cesium (Cs), methylammonium (MA), and formamidinium (FA). As a result, it is seen that cation engineering is a viable solution to fine-tune the bandgap and prevent a photoinduced segregation. Moreover, a champion efficiency of 18.3% is reported with a 1.67 eV bandgap.