静水压对立方钙钛矿CsSnX3(X=I, Br, Cl)光电性质的第一性原理探究

全无机无铅卤化物钙钛矿已经成为重要的新一代太阳能电池材料.采用密度泛函理论的第一性原理研究了不同静水压下CsSnX₃(X=I, Br, Cl)材料的晶体结构，电子结构和光学性能，并分析了其内在联系.结果表明施加静水压可使材料中Sn-X键长减小，使原子之间的耦合增强，带隙值减小，且随着卤族元素半径的增大，压力效应越明显；随着压力的增加，材料的吸收系数和复折射率增大，吸收光谱出现红移现象，在可见光区和近红外光区吸收增强.相比CsSnBr₃和CsSnCl₃,CsSnI₃在可见光区吸收最佳且受压力作用影响最小，更适用于钙钛矿太阳能电池材料.

First-principles study of photoelectric properties of cubic perovskite CsSnX3(X=I, Br, Cl) under hydrostatic pressure

All-inorganic and Pb-free halide perovskites have become an important new generation of solar cell materials. In this work, we investigated the crystal structures, electronic structures and optical properties of CsSnX3 (X = I, Br, Cl) materials under different hydrostatic pressures and analyzed their intrinsic relations by using the first principles method based on the density functional theory. The results show that the applied hydrostatic pressure reduces the length of Sn-X bond, resulting in the enhancement of interatomic coupling and then a decrease in the band gap value. Further, the pressure effect becomes more obvious as the radius of halogen atoms increases. With increasing the pressure, the values of absorption coefficient and complex refractive index are increased. Moreover, the absorption spectrum is red-shifted and the absorption in the visible and near infrared regions is enhanced. Compared with CsSnBr3 and CsSnCl3, the CsSnI3 has the best absorption in the visible region and is least affected by pressure. Therefore it is more suitable for perovskites solar cell materials.