Scrutinized the spin-orbit coupling effect on the elastically and thermodynamically stable Rb2BCl6 (B = Pb, Ti) double perovskites for photocatalytic, optoelectronic and renewable energy applications

Abstract

In this report, the electronic structure, mechanical stability, optoelectronic, thermoelectric and photocatalytic response of inorganic halide perovskites Rb2BCl6 (B= Pb, Ti) have been simulated first time by using density functional theory (DFT). Modified Becke-Johnson (mBJ) potential along with spin-orbit coupling (SOC) effect is applied for accurate calculations. The calculated ground-state lattice parameters, negative formation energy values and positive phonon frequencies endorse the stability of both compounds. The band structure plots display the semiconductor character of both perovskites. The mechanical stability has been determined with the Bulk and Young modulus, Poisson ratio, along with the calculation of elastic constants. The calculated optical response reveals a high dielectric constant and absorption coefficient with low reflectivity. These compounds are revealed to have a higher figure of merit (ZT) than the typical metal halide perovskites with the values of 0.732 and 0.72 for Rb2PbCl6 and 0.724 and 0.71 for Rb2TiCl6 at 800K with mBJ and mBJ+SOC, respectively. The Seebeck coefficient and figure of merit present good values at high temperatures. The photocatalytic activity has shown the water-splitting ability of Rb2TiCl6. The overall analysis of the calculated properties shows that the studied halide perovskites are suitable for optoelectronic, thermoelectric and photocatalytic applications.