Revealing the Role of Potassium Treatment in CZTSSe Thin Film Solar Cells

Wenjie Li, Zhenghua Su, Joel Ming Rui Tan, Sing Yang Chiam, Hwee Leng Seng, Shlomo Magdassi, Lydia Helena Wong*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


Potassium (K) post-treatment on CIGSSe has been shown to yield the highest efficiency reported to date. However, very little is known on the effect of K doping in CZTSSe and the mechanism behind the efficiency improvement. Here we reveal the mechanism by which K enhances the charge separation in CZTSSe. We show that K accumulates at the CdS/CZTSSe, passivating the recombination at the front interface and improving carrier collection. K is also found to accumulate at the CZTSSe/Mo interface and facilitates the diffusion of Cd into the absorber which affects the morphology and grain growth of CZTSSe. As revealed by the C-V, external quantum efficiency, and color J-V test, K doping significantly increases the carrier density, improves carrier collection, and passivates the front interface and grain boundaries, leading to the enhancement of Voc and Jsc. The average power conversion efficiency has been promoted from 5% to above 7%, and the best 7.78% efficiency has been achieved for the 1.5 mol % K-doped CZTSSe device. This work offers some new insights into the K doping effects on CZTSSe via solution-based approach and demonstrates the potential of facile control of K doping for further improvement of CZTSSe thin film solar cells.

Original languageAmerican English
Pages (from-to)4273-4281
Number of pages9
JournalChemistry of Materials
Issue number10
StatePublished - 23 May 2017

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© 2017 American Chemical Society.


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