Nonlinear optical-dielectric dual switching and narrow band gap in a one-dimensional hybrid compound: [(CH3)2S(CH2)3NH3][SbBr5]

Abstract

Organic–inorganic hybrid structural phase-transition compounds have attracted significant attention in recent years due to their excellent optoelectronic properties and potential for multifunctional switchable applications. Seeking such materials and studying the relationships between their changeable physical properties and crystal structures are of great importance for promoting their applications. Herein, we report a new one-dimensional, lead-free organic–inorganic hybrid compound, [(CH₃)₂S(CH₂)₃NH₃][SbBr₅] [where [(CH₃)₂S⁺(CH₂)₃NH₃]⁺ = dimethyl(3-propylammonium)sulfonium dications], which undergoes a structural phase transition from the centrosymmetric space group of Pcnm (high temperature) to the polar orthorhombic space group of Pca2₁ (low temperature) and exhibits a large second harmonic generation intensity that is 2.32 times that of KH₂PO₄, accompanied by switchable non-linear optical and dielectric properties. Structural analyses demonstrate that the structural phase transition was triggered by the ordering of the organic cations and the distortions of the inorganic octahedra. Moreover, pyroelectric measurements indicate that the compound should be ferroelectric, and UV-vis absorption and density functional theory calculations reveal a narrow band gap of 2.29 eV (calculated value = 2.06 eV). This work may offer an approach for designing organic–inorganic hybrid compounds with advanced multifunctional properties.