How Chloride Suppresses Photoinduced Phase Segregation in Mixed Halide Perovskites

Abstract

Halide\nion mobility in metal halide perovskites plays an important\nrole in dictating the overall device performance and long-term stability\nof perovskite solar cells. Alloying with chloride (Cl), which is known\nto stabilize the perovskite solar cells, has now been found to suppress\nthe photoinduced halide ion segregation in mixed halide (Br/I) perovskites.\nBy varying the chloride concentration of 1–10% (as part of\nthe halide composition), we have probed both photoinduced segregation\nand dark recovery kinetics at different temperatures. When we increased\nthe concentration of Cl from 0 to 5%, we observed a decrease in the\nrate constant of segregation by a factor of ∼5 and a decrease\nin the fraction of halide segregation from 45 to 20%. The activation\nenergy for photoinduced halide segregation increases (∼4 kJ/mol)\nupon the introduction of chloride into the mixed halide film, reflecting\nan increased energetic barrier for halide ion migration.