First Principle Investigation of Electronic, Optical, and Mechanical Properties of TlMCl₃ (M= Ca, Cd) Under Pressure

Thallium (Tl)-based halide perovskites have developed as a hopeful candidate for various optoelectronic uses including solar cells, LEDs, photodetectors, etc. for their distinctive optical and electrical properties. TlMCl<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> (M=Ca, Cd) are studied under the force of hydrostatics differing from 0 to 125 GPa and 0 to 200 GPa utilizing first-principles methods. The bandgap of TlCaCl<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> reduced from 3.953 eV to 1.924 eV under variation in pressures between 0 and 125 GPa causing an UV to visible area transition. The bandgap of TlCdCl<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> is reduced from 1.789 to 0 eV via changing pressure from 0 GPa to 200 GPa and the compound became metallic at 200 GPa. An increasing tendency of optical absorptivity, conductivity, and reflectivity is observed in both compounds under pressure. Both compounds are mechanically stable, and the ductility also increases with the applied pressure.