N-Bromosuccinimide as an interfacial alleviator for Br/I exchange in perovskite for solar cell fabrication

Engineering the surface at the rear interface between the perovskite and the hole transporting material is of paramount importance to minimize non-radiative losses. We report the use of N-bromosuccinimide (NBS), as an interfacial alleviator to influence crystallization of the perovskite and defect passivation. The NBS treatment promotes added charge extraction and yields devices with improved photovoltaic performance. Thus formed perovskite layers exhibit grain size increment and lowered trap density. An improved device performance was noted with an optimized concentration of 0.5% NBS as compared to pristine perovskite due to the open circuit voltage and short circuit current density enhancement. The coordination of bromide influences the crystal lattice as shown by polarization modulated-infrared reflection-absorption spectroscopy, which in turn may influence charge transport and interfacial properties.