Electronic Structure, Optical and Thermal Response of Lead-Free RbAuBr ₃ and RbAuBr ₄ Perovskites for Renewable Energy Applications

The presence of toxic lead in the perovskites is the major hurdle in commercializing these novel materials-based devices. The first principles calculations have been conducted to investigate the electronic structure, optoelectronic, and transport properties of lead-free RbAuBr 3 and RbAuBr 4 perovskites. Modified Becke-Johnson approximation is used to evaluate the accurate band structures for both compounds. The calculated energy-volume curves and the negative formation energy values confirm their stability. The band structure profile shows a semiconductor nature of both compounds with bandgap values of 0.77 eV and 2.32 eV for RbAuBr 3 and RbAuBr 4 , respectively. The density of states graphs endorsed the band structure results. The optical response is calculated in terms of real and imaginary parts of the dielectric function, refractive index, and energy loss parameters. The maximum absorption is achieved in the infrared region for RbAuBr 3 and the visible region for RbAuBr 4 . The thermoelectric response is also computed and a high ZT value of 0.96 is achieved for RbAuBr 3 , while a moderate value of 0.60 is obtained for RbAuBr 4 at 800 K. The calculated properties reveal the potential of studied lead-free perovskites for thermoelectric and optoelectronic applications.

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