Composition engineering of a Cu2ZnGexSn1−xS4 nanoparticle hole transport layer for carbon electrode-based perovskite solar cells

Composition engineering via alloying Cu 2 ZnSnS 4 and Cu 2 ZnGeS 4 is studied to optimize the properties of a Cu 2 ZnSn 1− x Ge x S 4 hole-transporting layer, which contributes to carbon electrode-based perovskite solar cells with a champion efficiency of 19.8%.