The electronic and optical properties of Cs2 Ti1-xBxI6(B=Sn, Te, Se) with first principle method

Abstract

Lead-free halide perovskite is regarded as the most promising light-harvesting material for solar cells recently. In this work, the properties of CsTiBI (B=Sn, Te, Se) were investigated with first principle method based on density functional theory. The results show that CsTiSnI is an excellent photoelectric material in the sunlight. When the doping concentration was over , CsTiSeI and CsTiTeI have direct–indirect band gap transition. The values of energy gap, density of states and optical absorption coefficients in the visible light region are well matched to each other. Optical results show that absorption peaks locate near 330 nm and have strong ultraviolet absorption capacity. Doping Sn results in the spectrum redshifts and the absorption peak drops. While the peak becomes greater with the increase of tellurium, and the spectrum has obvious blueshift. The spectrum trends of CsTiSeI are more complicated. This work provides theoretical supports for the development of novel optoelectronic materials by means of partial substitution doping.