Halogen engineering tuned band gap and structural phase transition in lead iodide hybrid perovskite semiconductors†

Organic–inorganic hybrid materials possess unique advantages, including structural adjustability and tunable functional properties, making them promising candidates for applications in sensors, intelligent switches, and optoelectronic devices. In this study, we investigate the impact of halogen tuning on the macroscopic properties of three 1D (one-dimensional) perovskite semiconductor hybrids: [RCM3HQ]₂PbI₄ (1), [RBM3HQ]₂PbI₄ (2), and [RIM3HQ]₂PbI₄ (3) (where RCM3HQ = R-N-chloromethyl-3-hydroxylquinuclidinium, RBM3HQ = R-N-bromomethyl-3-hydroxylquinuclidinium, and RIM3HQ = R-N-iodomethyl-3-hydroxylquinuclidinium). As anticipated, halogen tuning facilitates the regulation of structural phase transitions, with hybrid 1 exhibiting a phase transition accompanied by a dielectric switch. Notably, halogen engineering alters the band gap significantly, decreasing it from 2.75 eV (1) to 2.35 eV (3). Furthermore, all compounds 1–3 demonstrate a response to X-ray radiation detection and exhibit good photocurrent stability. Our findings present an effective molecular design strategy for optimizing the properties and exploring high-performance multifunctional semiconductor materials.