Halogenation triggering rules in hybrid materials for fluorescence and dielectric phase transitions

Abstract

Organic–inorganic hybrid materials with controllable physicochemical properties have played a great role in multifunctional sensors, photovoltaic cells, switching devices, etc. Among them, organic–inorganic hybrid dielectric materials have become a hot research topic within current cross-frontier research. In order to unveil the effect of halogen ions on phase transitions, we synthesized three hybrids: (TMBPA)CdCl₂Br (TMBPA-ClBr, 1), (TMBPA)₂CdBr₄ (TMBPA-Br, 2), and (TMIPA)₂CdI₄ (TMIPA-I, 3), (TMBPA = 3-bromopropyltrimethylammonium, TMIPA = 3-iodopropyltrimethylammonium). The phase-transition temperature of the three compounds increases with the size of the halogen ions from Cl⁻ to I⁻. Interestingly, the three compounds exhibit consistent trends in dielectric and photoluminescence properties, and the corresponding photoluminescence lifetimes are calculated as 1.55 ns, 1.28 ns, and 0.98 ns, expressing consistency with halogen regulation. This is very similar to the success of the cationic substitution of formamidinium/Cs/methylammonium lead iodide. Therefore, this work provides guidance for understanding the composition–structure–property relationship of organic–inorganic hybrid perovskites.