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Issue 26, 2016
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A band-gap-graded CZTSSe solar cell with 12.3% efficiency

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Although Cu2ZnSn(S,Se)4 (CZTSSe) has attracted attention as an alternative to CuInGaSe2 (CIGS) as an absorber material in solar cells, its low efficiency is a serious shortcoming preventing its commercialization. To realize a high-efficiency CZTSSe solar cell, improved grain crystallinity, inhibited secondary-phase formation, controlled defect generation, adequate Na content, and band gap grading are required in the absorber layer. Few studies have focused specifically on band gap grading. In this study, a method of using SeS2, a new potential chalcogenization source material, to control the S and Se contents in a CZTSSe absorber and its effects were investigated. Using an appropriate SeS2/Se weight ratio, band gap grading was realized within the depletion region. By increasing the value of VOC through band gap grading in the depletion region, a record VOC deficit of 0.576 V was achieved. Furthermore, the possibility of enhancing JSC through the formation of a type-inverted n-type phase at the absorber surface in response to an appropriate alignment of the conduction-band minimum energy level and the Fermi energy pinning level is discussed. By introducing the chalcogenization source material SeS2 during the annealing process, CZTSSe solar cells with a maximum efficiency of 12.3% were obtained.

Graphical abstract: A band-gap-graded CZTSSe solar cell with 12.3% efficiency

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Publication details

The article was received on 22 Feb 2016, accepted on 27 Apr 2016 and first published on 27 Apr 2016

Article type: Paper
DOI: 10.1039/C6TA01558A
Citation: J. Mater. Chem. A, 2016,4, 10151-10158
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    A band-gap-graded CZTSSe solar cell with 12.3% efficiency

    K. Yang, D. Son, S. Sung, J. Sim, Y. Kim, S. Park, D. Jeon, J. Kim, D. Hwang, C. Jeon, D. Nam, H. Cheong, J. Kang and D. Kim, J. Mater. Chem. A, 2016, 4, 10151
    DOI: 10.1039/C6TA01558A

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