Cation substitution in all solution-processed Cu2(Cd,Zn)SnS4 superstrate solar cells

Thin-film solar cells constituted of abundant elements are the key to ensuring mass production, reducing energy costs, and meeting energy demands. Kesterite, is a cost-effective light absorber, however showed low compatibility with a superstrate architecture, and has been studied mostly with the costly substrate. We demonstrate that a cation substitution of Zn by Cd improves the absorber compatibility on a superstrate architecture. Moreover, we employed all solution-processed using water and ethanol mixture as green solvents for thin-film deposition. An increase of the Cd amount in the absorber layer gave improved crystallinity and crystal size increment, band gap decrement, and a change in crystal structure from kesterite to cernyite. The composition of the buffer layer is controlled by the diffusion of Zn into CdS, forming (Cd,Zn)S with a relative Cd–Zn ratio. Solar cells prepared with high Cd showed a thicker depletion width and a reduction in the defect carrier density, lead to a significant increment in the power conversion efficiency up to 1.9%. Furthermore, the fabricated solar cells show high stability on continuous light illumination of over 80 hours. The investigation of the electrical losses in Cu2CdSnS4 suggests ample opportunity to improve the solar cell performance in a superstrate architecture