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

Solution-processed all-inorganic CsPbX 3 (X = Br, I, and Cl) perovskites are proven to be promising materials for various optoelectronic applications. However, CsPbX 3 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 CsPbBr 3 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. Modifying both the top and bottom surfaces of CsPbBr 3 perovskite films enhances carrier lifetime and optical gain remarkably.