Theoretical study on photoelectric properties of FAPbI3 doped with Ge

Abstract FAPbI 3 (NH 2 CHNH 2 PbI 3 ) is an organic-inorganic hybrid perovskite containing Pb, which has good photoelectric characteristics and great potential in the application of low-cost and high energy efficiency photoelectric devices. In order to reduce the pollution of Pb to the environment, the first-principles based on density functional theory(DFT) is used to compare and study the photoelectric parameters such as the band structure, density of states(DOS), absorption coefficient, reflectivity, conductivity and dielectric function of FAPb 1−x Ge x I 3 (x = 0.0,0.33,0.50,0.67,1.0). The results show that the 4p orbital electrons of Ge and the 6p orbital electrons of Pb and 5p orbital electrons of I are hybridized after doped with Ge, which change the band structure of FAPbI 3 . The result is that the optical band gap of the material is narrowed, the curvature of the band is increased, the effective mass of electrons and holes is reduced, the absorption peak of visible light increases and the absorption range increases. And the reflectivity and energy loss of the material also increase at the same time. The super SOC effect of the heavy metal Pb element leads to the splitting of the conduction band level of FAPbI 3 , the conduction band value drops sharply, and the band gap decreases sharply. We found that when the doping ratio of x in FAPb 1−x Ge x I 3 was between 0.55 and 0.65, the optimal band gap was between 1.3–1.4 eV. Therefore, reasonable regulation of Ge’s doping ratio can improve the photoelectric conversion efficiency of FAPbI 3 . This study can provide some theoretical guidance for experimental research and search for new efficient and environmentally friendly perovskite solar materials.