Ab-initio simulations of Rb2CuMCl6 (M = Sb, Bi) for photovoltaics and thermoelectric device applications

Abstract

Due to their extraordinarily flexible optoelectronic properties, the research on non-toxic double-perovskite halides has recently become very attractive. We use density functional theory to analyze the optical, electronic, and thermoelectric characteristics of copper-based double-perovskite halides, Rb2CuMCl6 (M = Sb, Bi). The band structures obtained with the Tran-Blaha altered Becke-Johnson potential demonstrate that altering the cations from Sb to Bi results in bandgap adjustments from infrared to visible (i.e. 1.0–1.2 eV) energy. Because of replacing Sb with Bi, the optical absorption exhibits utmost absorption within the ultraviolet region, whereas the absorption edge is shifted from infrared to the visible light region. Furthermore, the transport parameters are compatible with other estimated thermoelectric parameters. The fact that Rb2CuSbCl6 has a higher Seebeck coefficient indicates that a narrower band gap is appropriate for thermoelectric applications compared with Rb2CuBiCl6. In general, the Rb2CuMCl6 (M = Sb, Bi) is suitable for Sun-absorption devices and energy conversion, according to this computational thermoelectric and optical study.