Synergetic effect of tetraoctylammonium chloride in suppressing photoinduced phase segregation in mixed halide perovskite solar cells

Phase segregation, caused by halide ion migration under illumination, is a critical challenge limiting the commercialization of mixed-halide perovskites. In this study, a facile and effective strategy is introduced to mitigate photoinduced phase segregation in the FA_0.83Cs_0.17Pb(I_0.6Br_0.4)₃ mixed halide perovskite film by employing tetraoctylammonium chloride (TOAC) as both an additive and surface passivation for the first time. The results demonstrate that TOAC effectively reduces halide ion migration, stabilizes the perovskite phase, and suppresses phase segregation, particularly in the combined additive-passivation configuration. Mixed-halide perovskite solar cells fabricated with this dual TOAC approach achieve the highest efficiency of 15.8 %, with enhanced stability under continuous illumination and reduced hysteresis. The study highlights the critical role of TOAC in suppressing phase segregation, and improving the stability and performance of mixed-halide perovskite solar cells by addressing both surface and bulk defects, facilitating the development of more stable and efficient mixed-halide perovskite solar cells.