Recently, the teacher Chengyan Liu and Master Yingru Cui of Professor Yu Jia’s group make an advance in the improvement of open-circuit voltage of Kesterite solar cells.

As is well known, open circuit voltage (Voc) is considered to be a primary limiting factor of efficiency promotion in Kesterite solar cells, which significantly depends on the extent of band bending at the interface of absorber/buffer. It is found that a weak n-type kesterite surface is helpful to improve Voc in devices. Based on the doping limit rule, they found that Ag-based selenized kesterite (Ag₂ZnSnSe₄) facilitating the formation of n-type defects by lowering the conduction band is conducive to the stable weak n-type surface rather than suppressing the formation of p-type defects by lowering the valence band. Furthermore, they provide the weak n-type region in phase diagram of AZTSe, showing that Li doping can further weaken the n-type strength by forming the p-type LiZn defects which have the lowest formation energy, which greatly reduces the difficulty of experimental realization. This study presents that Ag-based selenized CZTSSe surface combined with Li post-treatment is a feasible way to realize the improvement of Voc in Kesterite semiconductors and provides a new scheme for the design of high efficiency solar cells.

The work “Band Edge Engineering for the Improvement of Open-Circuit Voltage: Ag-Based Selenized Cu₂ZnSn(SSe)₄ Surface Regulated by Lithium” has been published in the journal of Solar RRL (Sol. RRL 2021, 2000631) (IF=7.527, JCR District 1).

Article link: https://www.onlinelibrary.wiley.com/doi/10.1002/solr.202000631.

The first author of this paper is Master Yingru Cui of Key Laboratory of Special Functional Materials, and the corresponding authors are professor Yu Jia and distinguished professor Chengyan Liu. This work is supported by the National Natural Science Foundation of China and the Key Scientific Research Foundation for universities of Henan Province.