Light-Induced Surface Recombination Suppression, Carrier Lifetime Improvement, and Deep Defect Formation in Lead Halide Perovskites

Abstract

Lead halide perovskites are promising materials in a wide range of optoelectronic devices. The internal instabilities of perovskites under illumination, however, hinder their application. Here, light-induced changes in CH(3)NH(3)PbBr(3) single crystals are studied, focusing on charge carrier transport properties and deep defect evolution. Using laser-induced transient current technique measurements under steady-state illumination enables the distinction of electron and hole conductivity. An improvement in charge carrier collection is observed stemming from reduced surface recombination and increased hole lifetime. Surprisingly, despite the overall optimization of carrier transport, the simultaneous formation of deep defects under illumination is recorded via photo-thermal deflection spectroscopy. Empirical models are proposed to rationalize all light-induced changes. The explanations are based on strong electron trapping, ion migration, and passivation of strong recombination centers by light-induced deep defects.