Modulating the birefringence of two-dimensional hybrid lead bromide perovskites by pyridine derivative cations

Abstract

Birefringent crystals for modulating the polarization of light are of technological importance in optical communications. Herein we provide two novel two-dimensional hybrid halide perovskites, [(H2-dpys)(PbBr4)] (1) (dpys = di(pyridin-4-yl)sulfane) and [(H-cmpy)4(Pb3Br10)] (2) (cmpy = 4-chloro-3-methylpyridine), which can be acted as the birefringent crystals. It is remarkable that the crystal structures and the optoelectronic performance of the hybrid lead bromide perovskites are elaborately regulated by the organic cations of pyridine derivatives. Compound 2 constructed from the single pyridyl moiety of H-cmpy+ cations has a significantly enhanced birefringence (0.315@550 nm) compared to compound 1 (0.192@550 nm) with two pyridyl moieties of H2-dpys2+ cations, which is larger than all commercial birefringent crystals and most of hybrid metal halide perovskites. The results of the theoretical calculations showed that the highly distorted PbBr6 octahedrons and the delocalized π-conjugation of H-cmpy+ cations synergistically contribute the enhanced birefringence for 2. This work provides a useful strategy for modulation of the crystal structures and the optoelectronic performance of the hybrid lead halide perovskites.