Large Phase-Transition Temperature Enhancement Achieved in a Layered Lead Iodide Hybrid Crystal by H/F Substitution

The record T (tr) enhancement of148 K by H/F substitution has been achieved in a layered lead iodidehybrid crystal. Organic-inorganic hybrid metal halides with structuralflexibilityand solution processability have been widely investigated for differentapplication scenarios. However, the effective construction of phase-transitionmaterials with a high phase-transition temperature (T (tr)) for potential practical applications remains a greatchallenge, and reports on the regulation of T (tr) with significant enhancement have been rare. In this manuscript,we have realized a large T (tr) increaseof 148 K in a layered hybrid lead iodide crystal (4-FTMBA)(4)Pb3I10 (4-FTMBA = 4-fluoro-N,N,N-trimethylbenzenaminium) by the H/F substitution strategy. Comparedto the parent (TMBA)(4)Pb3I10 (TMBA= N,N,N-trimethylbenzenaminium), H/F substitutionpreserves the structural framework and crystal symmetry in (4-FTMBA)(4)Pb3I10. The introduction of heavierfluorine will significantly increase the motion barrier for the order-disordertransition, resulting in the remarkably improved T (tr). Temperature-dependent crystal structures, Raman spectra,and dielectric analyses well support the phase-transition behavior.In addition, evident thermochromism with a tunable direct band gapin (4-FTMBA)(4)Pb3I10 has been observedusing UV-vis spectra. To the best of our knowledge, the achieved T (tr) enhancement of 148 K by H/F substitutionis the highest among the organic-inorganic hybrid lead halidephase-transition materials. This finding would greatly inspire therational design of functional materials with high performance.

Automated summary

A record T (tr) enhancement of 148 K by H/F substitution has been achieved in a layered lead iodide hybrid crystal. This finding has significant implications for the rational design of functional materials with high performance. The H/F substitution strategy increases the motion barrier for the order-disorder transition, resulting in the improved T (tr) in the crystal.