Study of Structural Phase Transition and Optical Properties in (DMP)2MCl5 (M = Bi, Sb): A Novel 0D Hybrid Metal Halide

Abstract

In recent years, Bi/Sb-based lead-free hybrid organic-inorganic metal halide (OIMHs) with zero-dimensional (0D) structures have attracted unparalleled attraction owing to their low-cost, structural flexibility and efficient luminescence properties. These intriguing properties of 0D hybrid metal halides make them promising candidates for commercial applications in solar cells, LED applications, and X-ray detectors. [1] To further explore the 0D lead-free hybrid metal halides, herein we report two novel organic ammonium-based 0D lead-free metal halides, (DMP)2BiCl5 and (DMP)2SbCl5 that crystallize in the triclinic system with P̅1 space group and monoclinic system with P21/c space group, respectively. The crystal structure consists of discrete isolated [M2Cl10]4− (M = Bi, Sb) inorganic units encased by (DMP)+ organic cations as confirmed by single crystal study. The structural phase transition from monoclinic to triclinic phase is further studied through the synthesis of solid solution, (DMP)2Sb1−xBixCl5, by the substitution of Bi at Sb crystallographic site in pristine Sb compound. The effect of the structural phase transition on the optical properties like optical band gap, photoluminescence characteristics is also studied. The phase purity, structural phase transition, stability, and optical properties of the compounds are further discussed by various characterization techniques.