Broad-Band Emission in All-Inorganic Metal Halide Perovskite with Intrinsic Vacancies

Efficient broad-band emissions related to self-trapped excitons (STEs) in low-dimensional perovskites and double perovskite crystals have been attracted great attention due to their potential applications in optoelectronic. However, STEs in three-dimensional (3D) all-inorganic perovskites (CsPbX3) are generally accepted as difficult to form. Here, through doping ytterbium （Yb3+） or erbium (Er3+) ions in CsPbX3 crystals, we observe broadband luminescence of STEs with linewidth exceeding 200 nm and Stokes-shift of ~1 eV. Experiment-theory-combined study clarifies the Pb2+ in perovskite can be replaced by impurity ions, and the Pb2+ substitution defect and adjacent halide vacancy introduce defect states lying just below the conduction band minimum of perovskite. The strong electron-phonon coupling between the trapped carriers and the deformation of [PbX6] cage reduces the energy gap of perovskites. This study shed new light on the permanent defects induced extrinsic STEs in 3D inorganic perovskites and provides a clear microscopic picture of the underlying formation mechanism of STEs.