Reducing the Trap Density in MAPbI₃ Based Perovskite Solar Cells via Bromide Substitution

The past decade has witnessed tremendous advancement in the field of halide perovskite (PSK) as a choice of material for high-performing solar cells fabrication. Here, we investigate the impact of the halide exchange through N-bromosuccinimide (NBS) treatment in MAPbI₃ based solar cells. We observed the partial halide exchange (I^- to Br^- ) or the filling of halide (X^- ) vacancy upon treatment of different NBS concentrations experimentally by spectroscopic and diffractogram studies. We noted that halide exchange impacts the crystallization and is beneficial in improving the photovoltaic performance. The optimized 0.5 % NBS treated PSC exhibited a power conversion efficiency of 17.87 % due to an increment in open-circuit voltage (V_oc ) and short circuit current (J_sc ). We noted improved perovskite crystal growth upon Br^- substitution; eventually, it helps to lower the trap density, reducing non-radiative recombination and renders the enhancement of long-term stability of PSC.