Achieving long carrier lifetime and high optical gain in all-inorganic CsPbBr3 perovskite films via top and bottom surface modification

Abstract

Solution-processed all-inorganic CsPbX₃(X = Br, I, and Cl) perovskites are proven to be promising materials for various optoelectronic applications. However, CsPbX₃ films as optical gain media were confronted with unsatisfactory surface coverage and inferior photoluminescence performance when compared with their colloidal nanocrystal counterparts. Herein, we demonstrate a strategy for improving the optical properties via modification of both top and bottom surfaces of CsPbBr₃ films. The treated perovskite films show ultra-smooth morphology and a carrier lifetime of 44 ns, more than one order of magnitude longer than the untreated one. Meanwhile, a mixed polymer layer on the top of the perovskite film could combine surface passivation with symmetric waveguide effects, leading to an outstanding net gain coefficient of 694 cm⁻¹. These merits predict the great potential of all-inorganic perovskite films to support high efficiency charge transport or stimulated emission.