Enhancing the Performance of Cu₂ZnGeSe₄ Solar Cells with Metallic and Transparent Back Electrodes via Lithium Doping

This study investigates the effect of lithium doping — via a 10 nm LiF nano-layer — on Cu₂ZnGeSe₄ (CZGSe) kesterite absorbers prepared using sputtered metallic precursors. The optimally doped cells achieved a certified efficiency of 6.4% on Mo substrates with enhanced crystallinity and grain growth compared to undoped samples. Applying the same doping strategy to transparent back electrodes showed notable material improvements, opening a pathway for CZGSe integration into next-generation tandem photovoltaic devices — positioning UM6P at the frontier of Earth-abundant solar technology.