Trivalent Metal Chloride Doping for Interfacial Passivation and Enhanced Charge Transfer in Wide Bandgap Perovskite Solar Cells

Wide-bandgap (WBG) perovskites with high Br content suffer from halide segregation owing to defect-promoting ion migration. The resultant phase segregation causes energy and charge transfer from Br-rich to I-rich areas, resulting in a large voltage loss in WBG perovskite solar cells (PSCs). Herein, we report the multifunctional effects of trivalent metal chloride doping on the efficiency, stability, and charge transfer of WBG PSCs, which were monitored by using in situ photoabsorption and photoluminescence (PL) spectroscopy. Among the examined dopants (BiCl 3, SbCl 3, and InCl 3 ), InCl 3 effectively passivated the surface of the perovskite grains and prevented halide segregation with the addition of a small amount (1 mol %) to the precursor solutions. Consequently, the In-doped FA 0.8 MA 0.15 Cs 0.05 PbI 2 Br PSC (FA: formamidinium; MA: methylammonium; band gap: 1.73 eV) improved its power conversion efficiency from 16.06 to 17.54% owing to passivation and enhanced electron transfer at the bottom interface. Furthermore, the In-doped PSC exhibited dramatically improved stability during storage and voltage scanning. Our work highlights the critical role of dopants in the formation of WBG perovskite films and their electronic properties, offering a way to improve and stabilize WBG PSCs.