Characterization of a Novel Lead-Free Chiral Double Perovskite for Circularly Polarized Light Detection using Density Functional Theory

Metal-halide perovskites have found applications in solar cells due to their low cost compared to silicon solar cells and high photon conversion efficiency. If chiral organics are incorporated into their structure, metal-halide perovskites are also a promising alternative to standard methods for the detection of Circularly Polarized Light (CPL). Lead-halide perovskites are highly efficient as light absorbers, but suffer from poor stability and are environmentally toxic, so a lead-free alternative with similar photophysical characteristics is highly sought-after. We present a novel chiral and lead-free layered double perovskite, (S)-(−)-b-methylphenethyl-ammonium]4 CuBiI8. We simulated its structure using DFT as implemented in Quantum ESPRESSO (QE) and compared its Raman spectra to experiment. A compositionally identical compound, differing only in that Ag's are present in the Cu sites, was already known in the literature [D. Li, et al. Angew. Chem., Int. Ed. 60, 8415–8418 (2021).]. We obtained theoretical relaxed structures of both the Ag-based and Cu-based compounds and characterized their Raman peaks and electronic structure, and quantified their degree of structural distortion by calculating their octahedral distortion parameters.