Conditions of Photo-Induced Defect Generation and Their Luminescence in Two-Dimensional Lead Bromide Perovskites

Two-dimensional (2D) lead halide perovskites have great potential applications in some photoelectronic devices due to their better stability and strong quantum confinement effect. Their luminescence spectra are typically characterized by a sharp excitonic peak. However, this peak can be severely attenuated by laser irradiation, along with additional broadband emissions on the low-energy side. This phenomenon poses a great challenge for practical applications, but the underlying physical processes are not yet clear. Herein, the conditions for the occurrence of broadband emission were carefully studied in 2D lead bromide perovskites (OA) 2 MA 2 Pb 3 Br 10 (OA = octylamine; MA = methylamine). We demonstrated that broadband emission occurs gradually under laser irradiation only when the temperature is above 280 K and the laser photon energy is greater than ∼2.7 eV (460 nm). The broadband emission was believed to be from photoinduced defects, and its two subcomponents were further attributed to the surface bromine vacancy (V Br ) and internal V Br . The poly(methyl methacrylate) coating can partially suppress the photoinduced defect generation. The conclusions may be applicable to other 2D perovskites and provide a reference to overcome their optical degradation.