First principles study on photoelectric properties of Tl-doped CuInS2 solar cell materials

As a direct energy gap I-III-VI semiconductor compound material, copper indium sulfur semiconductor thin film (CIS) has the significant advantages of high light absorption coefficient, thin thickness and low band gap, which is suitable for the preparation of photoelectric converter devices, and thus it has great potential in the field of thin-film solar cells. In this paper, the calculation models of protocell CIS and CIS doped with Tl (CIS:Tl) materials were constructed. The electronic structure and optical properties of protocell CIS and CIS:Tl materials were obtained by using the first principle calculation method. The calculation results show that both protocell CIS and CIS:Tl are direct band gap semiconductors, and it was found that doping Tl in CIS can adjust the band gap value of the electronic structure of semiconductor materials, so that the optimal band gap width of the solar absorption spectrum was achieved. The band gap of CIS:Tl material is 33.4% lower than that of protocell CIS. In addition, doping Tl can shifts the absorption peak of CIS to the high-energy region, and the absorption intensity of the main solar absorption peak is increased by 8.4%, which significantly enhances the light absorption capacity of copper indium sulfur semiconductor solar cells. Compared with the original cell CIS, the real peak of conductivity of Tl doped CIS is increased by 10.06%, which effectively improves the crystallization degree of the film and the efficiency of solar cells.