Pressure Driven Optical Transitions in Columnar-Ordered Cs2AgPdCl5: Phase Transformation-Independent Piezochromism

Hybrid perovskites have garnered significant attention in the scientific community due to their high power conversion efficiency achieved within a short period. However, most of these perovskites either contain toxic lead or exhibit instability in air and under UV–vis light. Halide double perovskites have attracted immense attention as an alternative class of materials to replace lead-based semiconductors for advanced optoelectronic applications. Using density functional theory, we studied a new double perovskite, viz. Cs2AgPdCl5, with a unique columnar-ordered arrangement of B-site cation and investigated its structural, electronic, and optical properties under the influence of hydrostatic pressure. We also examined the effect of hydrostatic pressure on Spectroscopic Limited Maximum Efficiency (SLME), which is found to increase with pressure and rises above 20% at 20 GPa. The significance of this theoretical investigation is that we have found halide double perovskites that demonstrate piezochromism without phase transformation and approach the Shockley-Queisser limit for bandgap in the pressure range of 6–12 GPa. Moreover, this is the first time we have found a maximum reflectivity in an inorganic halide double perovskite material under the influence of external hydrostatic pressure without any possible phase transformation.