Study on the Mechanisms of Na Doping in CIGSe Solar Cells via a Solution-Based Method

This study introduces a solution-based method for alkali metal doping in CIGSe solar cells. The effects of different Na doping procedures using NaF solution on the performance of CIGSe solar cells as well as CIGSe thin films were thoroughly investigated. Doping with Na was found to have a significant impact on the surface morphology and composition of CIGSe, effective passivation of the CIGSe/CdS interface, and resolution of grain boundary defects in CIGSe films. As a consequence, these changes resulted in decreased recombination, increased p-type conductivity in the surface layer, and the formation of high-quality p–n junctions. Significantly, solar cells subjected to Na post-treatment exhibited a remarkable 13% enhancement in power conversion efficiency.