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

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 ( increment H-f) 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 alpha (omega) 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.