Advancing kesterite absorbers with bronze-based precursors through physical deposition routes: a step toward stable and sustainable industrial photovoltaic technology

This work presents, for the first time, a direct comparison of the impact of applying elemental metallic stack precursors and bronze-based precursors to produce Cu₂ZnSnSe₄ (CZTSe)-based solar cells by sequential fabrication based on physical deposition methods. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction reveal an improved morphology, a higher compositional homogeneity, and a higher presence of binary alloys in the bronze-based precursor. Scanning electron microscopy observation also shows that bronze-based precursors improve the thickness homogeneity and the rear interface morphology of CZTSe absorbers, while Raman spectroscopy detects an improved crystalline quality and an improved structural micro-homogeneity at the absorber surface. The results of this work also demonstrate that germanium doping, which is required when applying elemental metallic stack precursors, can be avoided in the case of bronze-based precursors without compromising the efficiency of the solar cells. Thus, this work sheds light on the mechanisms induced by bronze-based precursors that contribute to producing high-efficiency CZTSe-based devices, so the expanded understanding of this precursor can help to further optimize such devices. Additionally, this work demonstrates that the bronze-based precursor reduces material, energy, and time consumption, which favors its possible scaling up to an industrial level.