Lead-free, mixed tin-copper perovskites with improved stability and optical properties

•Methylammonium bimetallic halide perovskites based on tin and copper were synthesized and characterized.•The Sn0.5:Cu0.5 system exhibits great potential with improved environmental stability, tailorable optical properties and facile processing methods implying its capability in optoelectronic applications. Tin halide perovskites are evolving as alternate materials to conventional, lead-based perovskites. Here, we report the synthesis of methylammonium bimetallic halide perovskites based on Tin and Copper. The perovskite structure was studied using X-ray diffraction (XRD) analysis. The substitution of Tin with Copper led to a 2D perovskite structure and a 3D structure with the change in the lattice spacing. The synthesized materials were characterized using field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and XRD studies. The thermal stability and environmental stability were investigated using thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). UV-Visible absorption spectra of mixed Tin-Copper perovskites exhibit absorption over the entire visible spectrum with a bandgap of 1.80 eV, comparable to that of lead-based perovskites. Luminescence and the charge carrier lifetime of the materials were investigated and are favourable for photovoltaic applications. Our study represents an alternative pathway to develop benign and stable organic-inorganic hybrid material for optoelectronic applications.