High-throughput screening to modulate electronic and optical properties of alloyed Cs2AgBiCl6 for enhanced solar cell efficiency

Abstract

The lead-free double perovskite material (viz. Cs2AgBiCl6) has emerged as an efficient and environmentally friendly alternative to lead halide perovskites. To make Cs2AgBiCl6 optically active in the visible region of solar spectrum, band gap engineering approach has been undertaken. Using Cs2AgBiCl6 as a host, band gap and optical properties of Cs2AgBiCl6 have been modulated by alloying with M(I), M(II), and M(III) cations at Ag-/Bi-sites. Here, we have employed density functional theory (DFT) with suitable exchange-correlation functionals in light of spin-orbit coupling (SOC) to determine the stability, band gap and optical properties of different compositions, that are obtained on Ag-Cl and Bi-Cl sublattices mixing. On analyzing 64 combinations within Cs2AgBiCl6, we have identified 19 promising configurations having band gap sensitive to solar cell applications. The most suitable configurations with Ge(II) and Sn(II) substitutions have spectroscopic limited maximum efficiency (SLME) of 32.08% and 30.91%, respectively, which are apt for solar cell absorber.