Homochirality to design high-Tc lead-free ferroelastic semiconductors

Abstract

Ferroelastic semiconductor materials have garnered significant research interest due to their promising applications in the fields of shape memory, superelasticity, templated electronic nanostructures, mechanical switching, and optoelectronic transmission. However, the toxicity of lead-based structures and low phase-transition temperature (T_c) greatly constrain the application scenarios of ferroelastic semiconductors. Here, using an H/OH-substitution-induced homochiral strategy, we synthesize a pair of lead-free ferroelastic semiconductors (R/S-CTA)₂SbCl₅ (CTA = 3-chloro-2-hydroxypropyltrimethyllammonium) having semiconductor properties with an indirect bandgap of 3.41 eV. They crystallized in the chiral space group P2₁2₁2₁ at room temperature, and both undergo 422F222 type ferroelastic phase transitions with T_c up to 410 K, accompanied by a large entropy change of 68.75 and 66.09 J mol⁻¹ K⁻¹, respectively. Owing to the introduction of chirality, they exhibited temperature-dependent nonlinear second-harmonic generation (SHG) properties. Relatively, the achiral TMCP (TMCP = N,N,N-trimethylchloropropylamine) makes the phase transition properties of centrosymmetric TMCP₂SbCl₅ ordinary compared to chiral R/S-pair. This is precisely the main starting point of homochiral strategies in phase transition and optical structure research, while arousing research interest. This work, which provides a new avenue for the design of high-T_c lead-free ferroelastic semiconductor compounds, is a powerful motivation for the realization of multifunctional materials related to chirality.