A first-principles study of exciton self-trapping and electric polarization in one-dimensional organic lead halide perovskites

Abstract

Revealing the origin of self-trapped excitons is a prerequisite for further improving the photoluminescence efficiency of low-dimensional organic perovskites. Here, the microscopic formation mechanism of intrinsic self-trapped excitons in one-dimensional (1D) C₄N₂H₁₄PbX₄ (X = Cl, Br and I) systems is investigated, and the polarization–luminescence relationship is established. Our results show that 1D-C₄N₂H₁₄PbX₄ has a low electronic dimension (flat band characteristics), which facilitates the formation of intrinsic self-trapped excitons. The potential well formed by local distortion of the [PbX₆] octahedron is the origin of exciton self-trapping. Combined with the electronic density of states and partial charge density, we further confirmed the existence of intrinsic self-trapping excitons in 1D-C₄N₂H₁₄PbX₄. In addition, we found that the breaking of the central inversion symmetry will induce electric polarization, which greatly improves the transition probability of electrons. These results could potentially offer a new direction for improving the luminescence properties of 1D organic lead halide perovskites.