Enhanced phase transition temperature achieved by CH3/H substitution in Sn-based perovskite

•Structural modification of the organic component significantly increased the phase transition temperature to 179 K.•The synergistic effect of cationic order-disorder motion and anionic framework displacements collectively triggers the phase transition.•A high phase transition temperature, environmentally friendly Sn-based perovskite with dielectric responsiveness. Organic-inorganic hybrid phase transition materials have garnered significant attention due to their excellent properties and broad applications in energy storage, temperature control switches, and optoelectronic devices. The regulation of the phase transition temperature (Tc) is necessary as it determines the properties and applications of materials. (TMTBA)2SnBr6 (1) (TMTBA = N,N,N-trimethyl‑tert-butylammonium) was synthesized, featuring the Tc around 225 K and then (DMTBA)2SnBr6 (2) (DMTBA = N,N-dimethyl‑tert-butylaminium) was obtained. Progressively, the 2 exhibited a great enhancement of Tc at 404 K, with a ΔTc reaching up to 179 K. Single-crystal structure analysis confirmed that 1 underwent isomorphic phase transitions, with the space groups of Pnma. In contrast, 2 underwent an order-disorder phase transition, and the space group changed from the low-temperature phase of I2/c to high-temperature phase of R3¯. What's more, the semiconductor properties and optical band gap of the materials were also investigated, 2.59 eV for 1 and 2.65 eV for 2. It is believed that this work can enrich the field of phase transition materials and provide some guidance for the regulation of Tc. [Display omitted]