A high phase transition temperature organic-inorganic Sn(IV)-based metal halide designed by amino position isomerism of cation

Abstract

Organic-inorganic metal halides (OIMHs) have recently received extensive interest from researchers because of their diverse functionalities, such as phase transition. A high phase transition temperature (T_c) is highly desirable for the practical applications of OIMH phase transition materials. Here, by applying cation amino positional isomerism to the lead-free Sn(IV)-based OIMH [n-butylammonium]₂SnCl₆ ([NBA]₂SnCl₆) which has a relatively low-T_c of 226 K, a high-T_c [sec-butylammonium]₂SnCl₆ ([SBA]₂SnCl₆) was successfully designed with T_c as high as 430 K. Such a high T_c of [SBA]₂SnCl₆ is higher than those of most lead-free OIMHs, and is outstanding among OIMHs. [NBA]₂SnCl₆ and [SBA]₂SnCl₆ are isostructural at room temperature, but differ in the hydrogen bond interactions, which could contribute to the differences in T_c. Additionally, the variation in phase transition mechanisms also constitutes a reason. In addition, [NBA]₂SnCl₆ and [SBA]₂SnCl₆ also have wide band gaps (E_g) of about 3.92 eV and 3.95 eV respectively. This work provides a new strategy for designing high-T_c OIMH materials.