Oxidative Passivation of Metal Halide Perovskites

Metal halide perovskites have demonstrated extraordinary potential as materials for next-generation optoelectronics including photovoltaics and light-emitting diodes. Nevertheless, our understanding of this material is still far from complete. One remaining puzzle is the phenomenon of perovskite "photo-brightening". the increase in photoluminescence during exposure to light in an ambient atmosphere Here, we propose a comprehensive mechanism for the reactivity of the archetypal perovskite, MAPbI(3), in ambient conditions. We establish the formation of lead-oxygen bonds by hydrogen peroxide as the key factor leading to perovskite photo-brightening. We demonstrate that hydrogen peroxide can be applied directly as an effective "post-treatment" to emulate the process and substantially improve photoluminescence quantum efficiencies. Finally, we show that the treatment can be incorporated into photovoltaic devices to give a 50 mV increase in open-circuit voltage, delivering high 19.2% steady-state power conversion efficiencies for inverted perovskite solar cells of the mixed halide, mixed cation perovskite FA(0.83)Cs(0.17)Pb(I-0.Br-9(0.1))(3).