Synthesis, characterization and optoelectronic properties of chemically stable (CH3)3SPbI3−xBrx and (CH3)3SPbI3−xClx (x = 0, 1, 2, 3) perovskites

Abstract

We report on the novel series of (CH3)3SPbI3−xBrx and (CH3)3SPbI3−xClx (x = 0, 1, 2, 3) perovskite compounds. X-ray diffraction analysis shows that the solid solutions of (CH3)3SPbI3−xBrx (x = 0, 1, 2, 3) and (CH3)3SPbI3−xClx (x = 0, 1, 2) crystallize in hexagonal symmetry (space group P63mc, No. 186) with 1D columns of face-sharing [PbX6] octahedra. (CH3)3SPbCl3 crystallizes in orthorhombic symmetry (space group Pnma, No. 62) forming 3D network of vertex- and face-sharing [PbCl6] octahedra. Optical and vibrational properties were investigated using UV–vis reflectance, photoluminescence and Raman spectroscopy at room temperature. The compounds show high chemical stability in ambient air at temperatures up to 80 °C and under solar simulator, in contrast to the hygroscopic CH3NH3PbI3 or CH(NH2)2PbI3 that are commonly used in perovskite solar cells. First principles theoretical ab initio and efficient semiempirical extended Hückel calculations were performed to evaluate the energy band gap values, whose results are in good agreement with the experimentally determined values.