Effect of Alkali Doping Strategies on the Performance of Wide Band Gap Cu2ZnGeSe4 Thin Film Solar Cells

In this work, the effect of different alkali doping strategies in kesterite Cu
₂
ZnGeSe
₄
absorbers is studied, including the impact on the structural and morphological characteristics of the semiconductor material, and the optoelectronic properties of the solar cell devices. The studied alkali elements include Li, Na, and K, and are introduced by two main approaches: post-deposition treatment (PDT), and pre-absorber synthesis (PAS). This study shows that PDT strategies are more interesting than PAS, and Li as the best alkali candidate for the further improvement of Cu
₂
ZnGeSe
₄
devices performance.