Photoconversion Efficiency of Polar Double Iodide Perovskite (CsRb)(GeSn)I₆: Theoretical Investigation

Achieving high power conversion efficiencies (PCEs) in ferroelectric photovoltaics (PVs) is challenging due to recombination issues associated with the large bandgaps of ferroelectric oxide perovskites. A key strategy to address this is reducing the bandgap, albeit with potentially decreased light absorption. Halide perovskites, with their narrow bandgaps and high absorption coefficients, present a promising alternative for solar cell applications. This study investigates the electronic and optical properties of the polar (CsRb)(GeSn)I₆ material using first-principles density functional theory (DFT). Our results demonstrate that (CsRb)(GeSn)I₆ exhibits a direct bandgap and high absorption coefficient, making it an excellent candidate for optoelectronic applications. Furthermore, we assess its photovoltaic performance using the spectroscopic limited maximum efficiency (SLME) model. The ferroelectric polarization in (CsRb)(GeSn)I₆ induces a potential gradient that enhances electron-hole separation, resulting in a SLME of 25.5%. These insights highlight the potential of (CsRb)(GeSn)I₆ and similar materials as high-performance semiconductors for solar cells and other optoelectronic devices. Our theoretical study offers valuable guidance for experimental research on ferroelectric perovskites in photoelectric applications.