Synthesis of two-dimensional phenylethylamine tin-lead halide perovskites with bandgap bending behavior

Recently, two-dimensional (2D) metal halide perovskite materials with wide application in perovskite-based solar cells have attracted significant attention. Among them, 2D mixed lead-tin perovskites have not been systematically explored. Herein, we synthesize a 2D phenethylammonium (PEA) tin-lead bromide perovskite, PEA₂Sn Pb_1- Br₄, via a simple solution-phase approach without toxic reagents and high temperatures. By tuning the ratio of Sn and Pb, the UV-vis absorption spectra showed unique bandgap bending behaviors. DFT calculations indicate the key effects of spin-orbital coupling (SOC) without the interference of lattice distortion. Moreover, we provided the standard equation with a correction term to introduce the influence of SOC. These results not only provide a step forward towards the bandgap engineering of perovskites, but also help to expand the application of 2D perovskite materials.