Optimization of Selenization Condition for Efficiency CIGSe Solar Cells Based on Postselenization of CuInGa Precursors

The degree of selenization of the CIGSe absorbers is controlled by regulating the parameters of the selenization reaction. The structure, element distribution, phase composition of the CIGSe absorbers, and the performances of the solar cells with different selenization degrees are studied. Insufficient selenization will lead to residual Cu₂Se phase on the surface and insufficient Na diffusion, which will affect the V_Cu⁺ on the surface and the recombination at the front interface. However, excessive selenization will make the MoSe₂ layer thicken at the back interface of the CIGSe/Mo, resulting in the increase of the series resistance and the enhancement of the recombination at the back interface. The appropriate selenization degree is conducive to inhibiting the recombination at the front and back interfaces. Improved device performances can be obtained by optimizing the selenization degree of the absorbers.