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.