Tuning Spin Texture and Spectroscopic Limited Maximum Efficiency through Chemical Composition Space in Double Halide Perovskites

The double halide perovskite family is emerging as a promising alternative to lead (Pb)-based hybrid perovskite materials not only in energy scavenging but also in spin-optoelectronic applications due to the inherent excellent stability, favorable charge carrier recombination rate, and nontoxicity. We have performed rigorous electronic structure calculations within the framework of density functional theory to envisage the electronic and optical properties along with the scrupulous determination of the spin texture for one such promising double halide perovskite system named Cs2AgBiBr6 under bismuth Bi-rich and antimony Sb-rich synthesis conditions. As this is the first time, to the best of our knowledge, the aforementioned properties are explored in Bi-rich and Sb-rich Cs2AgBiBr6, we have also investigated the structural and thermodynamic stability of the considered systems through the determination of tolerance factor, average octahedral factor, and octahedral mismatch. Interestingly, we have observed Rashba-like spin switching from the in-plane spin texture in the kx – ky plane centered at the Γ point despite the centrosymmetric crystal structure of Cs2AgBiBr6, which is remarkable for the double halide perovskite family. This particular finding could pave the way toward spin–orbitronics applications, while one can coin this phenomenon the pseudo-Rashba effect due to the absence of broken inversion symmetry. Additionally, in order to explore the applicability of these exciting systems in solar energy conversion, we have thoroughly investigated the spectroscopic limit maximum efficiency of the Bi-rich and Sb-rich systems with and without the inclusion of relativistic effects.