Dynamic tuning of optoelectronic and mechanical properties in TlMCl3 (M = Ge, Sn) under pressure-induced phase transition

<h2>Abstract</h2> Recent advances in lead-free halide perovskites have expanded their potential use in solar panels and optoelectronic applications. Motivated by their excellent properties, we investigate the physical characteristics of two lead-free halide perovskites, TlMCl₃ (M = Ge, Sn), under hydrostatic pressure. This paper explores the pressure-induced semiconductor-to-metal phase transition in halide perovskites TlMCl₃ (M = Ge, Sn), focusing on their optoelectronic and mechanical properties. Using density functional theory (DFT), the study investigates structural, electronic, optical, and mechanical changes under hydrostatic pressures up to 6.5 GPa. Both TlGeCl₃ and TlSnCl₃ maintain a cubic perovskite structure, but exhibit decreasing lattice parameters and unit cell volumes with increased pressure. Electronic analyses reveal a transition from semiconducting to metallic states for both materials under…