Trivalent\nMetal Chloride Doping for Interfacial Passivation\nand Enhanced Charge Transfer in Wide Bandgap Perovskite Solar Cells

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