Electronic, optical and thermoelectric performance of Cs₂AuXY₆ for photovoltaic applications: by DFT method

In this research work, the double perovskite Cs2AuXY6 (X = Sb, Bi; Y = Cl, Br) is explored as an absorber material in perovskite solar cells (PSCs). Computational simulations were performed by using Generalised Gradient Approximation along with Perdew-Burke-Ernzerhof (GGA-PBE) and modified Becke-Johnson (mBJ) exchange-correlation potential within the WIEN2K software to study the physical properties of Cs₂AuXY₆. Studied compounds have a cubic crystal structure with space group Fm3m (No 225). Electronic bandgap values for Cs2AuBiCl6, Cs2AuSbCl6 are 0.61, 0.24. Cs2AuBiBr6 is a semimetal (considering GGA-PBE) and has band gaps of 1.62, 1.12, and 0.59 eV (with mBJ), which are very close to the required band gap for solar cell applications according to the Shockley-Queisser limit. In addition to the above, the Optical result shows higher absorption and optical conductivity with minimal reflection in the visible and infrared regions, making them good absorbent materials for PSC. Moreover, the temperature-dependent thermoelectric nature of these compounds was explored by the BoltzTraP code, and the mechanical elastic constants were investigated by the charpin method, which follows the Born stability condition. Therefore, Cs₂AuXY₆-based PSCs are considered potential materials for charge transport layers, perovskite absorber layers, and conventional halide perovskite compounds.