Optoelectronic and thermoelectric characteristics of lead-free halide based double perovskites Rb2GaInX6 (X = Cl, Br, I) for solar cell applications

Abstract

For the fabrication of thermoelectric and optoelectronic devices, metal halide perovskite materials are perfect applicants. In this work, first-principles computation is carried out to explore the structural, optical, electronic, and transport features of Rb2InGaX6(X = Cl, Br, I).In structural calculations, the obtained value of Paugh’s ratio(B/G) reveals the material’s brittleness. The acquired negative value of enthalpy of formation (∆Hf) exposes the studied materials are stable. The exploitation of band structure exhibits that the Rb2InGaX6(X = Cl, Br) compound possesses an indirect bandgap value of 2.20eV for Cl, which significantly decreases to 0.90 eV by substituting anion from Cl up to I. The materials under observation possess a remarkable absorption coefficient α (ω) in ultraviolet and visible region (2–8eV) of light spectra, which makes it practical for photocell and optical device fabrication. Furthermore, the transport features are estimated by utilizing the BoltzTrap code within the temperature range of 200–500 K. The calculated value of the figure of merit (ZT) indicates that Rb2GaInX6 (X = Cl, Br, I) compounds are a potential candidate for thermoelectric device applications.