Computational insights into the superior efficiency of Cs2AgGa(Cl,Br)6 double halide perovskite solar cells

Abstract

Owing to their ecological integrity, non-toxicity, and outstanding performances, Double-Halide perovskites have been vigorously promoted as sustainable alternatives for thermoelectric and photovoltaic applications. In this context, we have systematically explored the structural and mechanical strength characteristics of Cs2AgGa(Cl,Br)6 materials through the tolerance factor analyses and Born stability criteria. Subsequently, a detailed study of their electronic, optical, and thermoelectric properties has been performed. As results, both Cs2AgGaCl6 and Cs2AgGaBr6 show semiconducting nature with a direct bandgap of about 2.57 eV and 1.42 eV, respectively. Additionally, with such desirable band gaps, the optical properties were examined based on the complex dielectric function. It has been derived that both materials exhibit a very high absorption spectrum in the order of 105 cm−1 and a low reflectivity not exceeding more than 18% in the visible and UV region. Furthermore, the Cs2AgGaBr6 has been taken into account as absorber to construct the planar p-intrinsic-n structure (FTO/TiO2/Cs2AgGaBr6/Spiro-OMeTAD/Au) and a high-record efficiency of 32.57% has been reached. The thermoelectric performance was also studied and revealed a very high Seebeck coefficient (thermo-power) and a sufficient figure of merit (ZT). Based on these results, we believe that the studied double-halide perovskites present outstanding performance for both optoelectronic and thermoelectric engineering devices.