The effect of Ge content on photovoltaic property of flexible Cu2ZnSn(S,Se)4 thin film solar cells
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Magnetron co-sputtering method followed by selenization was used for the preparation of Cu2Zn(Sn,Ge)(S,Se)4 (CZTGeSSe) thin film. The impact of Ge doping layer with different sputtering times on crystalline quality, surface roughness, band structure and device performance of CZTGeSSe absorber was systematically investigated. It was found that the increased Ge/(Ge + Sn) ratio could effectively promote the grain growth and improve the band mismatching of CZTGeSSe/CdS interface. The CZTGeSSe thin film with minimum roughness and increased CBO (− 0.54 to − 0.41 eV) was obtained with the increased Ge/(Ge + Sn) ratio of 7.3%. However, oversized grain with rougher surface could result in a non-uniform coverage phenomenon of CdS layer, leading to severe interface recombination. After optimizing the Ge/(Ge + Sn) ratio, the best device performance with an efficiency of 3.19% was achieved in flexible CZTGeSSe thin film solar cells.
The authors gratefully acknowledge National Natural Science Foundation of China (Grant no. 61774084), a project supported by the special fund of Jiangsu Province for the transformation of scientific and technological achievements (Grant no. BA2017032), the research fund of Jiangsu Province Cultivation base for State Key Laboratory of Photovoltaic Science and Technology (Grant no. SKLPSTKF201506) and funding of Jiangsu Innovation Program for Graduate Education (Grant no. KYCX18_0282).
- 22.Q. Shu, J.H. Yang, S.Y. Chen, B. Huang, H.J. Xiang, X.G. Gong, S.H. Wei, Phys. Rev. B 87, 268 (2013)Google Scholar