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, PEA(2)Sn(x)Pb(1−x)Br(4), 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.