Unraveling the Defect-Dominated Broadband Emission Mechanisms in (001)-Preferred Two-Dimensional Layered Antimony-Halide Perovskite Film.

By adding molar-controlled SbCl 3 in a Cs 3 Sb 2 Cl 9 precursor, we employed a low-temperature solution-processed approach to prepare high-quality (001)-preferred Cs 3 Sb 2 Cl 9 thin film, which demonstrates a stable defect-dominated broadband emission at room temperature. Density functional theory calculations reveal that the defect emission originates from the donor-acceptor pair (DAP) recombination between chlorine vacancy (V Cl ) and cesium vacancy (V Cs ). Furthermore, V Cl + V Cs DAP is more stable on the (001) surface. The improved film quality and the more stable V Cl + V Cs DAP increase the activation energy related to defect states, resulting in an enhancement of the defect emission for the high-quality (001)-preferred film. This work provides deep insight into the key role of the (001) surface in defect emission and a feasible strategy to enhance the defect emission in 2D halide perovskites A 3 B 2 X 9 (A = CH 3 NH 3 , Cs, Rb; B = Bi, Sb; X = Cl, Br, I) by control of the thin film preferred orientation.