Issue 2, 2022

Band-gap-graded Cu2ZnSn(S,Se)4 drives highly efficient solar cells

Abstract

Fabrication of highly efficient solar cells is critical for photovoltaic applications. A bandgap-graded absorber layer can not only drive efficient carrier collection but also improve the light harvesting. However, it is very difficult to realize such a bandgap-graded structure in kesterite-structured films due to the similar cation diffusion rates in the high-temperature selenization process. Here, we design and successfully realize a bandgap grade in Cu2ZnSn(S,Se)4 (CZTSSe) film by sufficient annealing during the deposition of an Al-doped ZnO film. This annealing strategy facilitates the solid-state ion-exchange reaction between Cu+ and Cd2+ at the heterojunction interface. Consequently, n-type CdS is partially converted to p-type Cu2S and CZTSSe is converted to Cd-graded CZTSSe, thereby forming a desired bandgap-graded CZTSSe solar cell. The tailored band alignment between the p–n junction not only improves the electron transport but also reduces the carriers recombination. As a consequence, the open-circuit voltage and fill factor are significantly improved, and a certified power conversion efficiency of 12.25% is obtained. The graded bandgap engineering of the absorber achieved here illuminates the future pathway towards highly efficient solar cells.

Graphical abstract: Band-gap-graded Cu2ZnSn(S,Se)4 drives highly efficient solar cells

Supplementary files

Article information

Article type
Paper
Submitted
06 Okt. 2021
Accepted
13 Des. 2021
First published
14 Des. 2021

Energy Environ. Sci., 2022,15, 693-704

Band-gap-graded Cu2ZnSn(S,Se)4 drives highly efficient solar cells

H. Guo, R. Meng, G. Wang, S. Wang, L. Wu, J. Li, Z. Wang, J. Dong, X. Hao and Y. Zhang, Energy Environ. Sci., 2022, 15, 693 DOI: 10.1039/D1EE03134A

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