Valence-Regulated Metal Doping of Mixed-Halide Perovskites to Modulate Phase Segregation and Solar Cell Performance

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Electronic doping is a promising approach to modulating the optoelectronic properties of semiconductors, but its effect on optoelectronic behaviors of halide perovskites remains controversial. Here, we comprehensively investigate the impact of Pb substitution in n-type CsPbIBr 2 perovskite by utilizing monovalent Ag, divalent Zn, and trivalent Sb. Our findings reveal that the trap densities in doped CsPbIBr 2 films are in the order of Ag < Zn < Sb. Compared with the pristine CsPbIBr 2, the Ag-doped perovskite features a significantly reduced phase separation; however, the Sb doping accelerates halide segregation, and Zn exerts a negligible influence. The p-doping effect from monovalent Ag can shift the Fermi level of CsPbIBr 2 toward the intrinsic midgap, which helps prevent the formation of ionic defects and reduce the migration of halide ions in the perovskite lattice. Through combing the density functional theory simulation, this study discloses the correlation between valence-controlled metal doping and phase segregation, providing a guideline for judiciously doping mixed-halide perovskites for optoelectronic applications.