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Secondary Phase and Defects in Cu2ZnSnSe4 Solar Cells with Decreasing Absorber Layer Thickness

  • Kim, Young-Ill (Research Center for Thin Film Solar Cells, DGIST) ;
  • Son, Dae-Ho (Research Center for Thin Film Solar Cells, DGIST) ;
  • Lee, Jaebaek (Research Center for Thin Film Solar Cells, DGIST) ;
  • Sung, Shi-Joon (Research Center for Thin Film Solar Cells, DGIST) ;
  • Kang, Jin-Kyu (Research Center for Thin Film Solar Cells, DGIST) ;
  • Kim, Dae-Hwan (Research Center for Thin Film Solar Cells, DGIST) ;
  • Yang, Kee-Jeong (Research Center for Thin Film Solar Cells, DGIST)
  • Received : 2021.04.13
  • Accepted : 2021.04.25
  • Published : 2021.09.30

Abstract

The power conversion efficiency of Cu2ZnSnSe4 (CZTSe) solar cells depends on the absorber layer thickness; however, changes in the characteristics of the cells with varying absorber layer thickness are unclear. In this study, we investigated the changes in the characteristics of CZTSe solar cells for varying absorber layer thickness. Five absorber thicknesses were employed: CZTSe1 2.78 ㎛, CZTSe2 1.01 ㎛, CZTSe3 0.55 ㎛, CZTSe4 0.29 ㎛, and CZTSe5 0.15-0.23 ㎛. The efficiency of the CZTSe solar cells decreased as the absorber thickness decreased, resulting in power conversion efficiencies of 10.45% (CZTSe1), 8.67% (CZTSe2), 7.14% (CZTSe3), 3.44% (CZTSe4), and 1.54% (CZTSe5). As the thickness of the CZTSe absorber layer decreased, the electron-hole recombination at the grain boundaries and the absorber-back-contact interface increased. This caused an increase in the current loss, owing to light loss in the long-wavelength region. In addition, as the thickness of the CZTSe absorber layer decreased, more ZnSe was produced, and the resulting defects and defect clusters led to an open-circuit voltage loss.

Keywords

Acknowledgement

This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) (No. 20173010012980), by the Technology Development Program to Solve Climate Changes of the National Research Foundation (NRF) funded by the Ministry of Science and ICT (2016M1A2A2936781), and by the DGIST R&D Programs of the Ministry of Science, ICT & Future Planning of Korea (21-ET-08).

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