The development of flexible solar cells is necessary for achieving market competitiveness through the implementation of low cost solar cells and for applying customized business models, such as Building Integrated Photovoltaics (BIPV). Solar cells with the CZTS-based (Cu2ZnSnS4, Cu2ZnSnSe4, Cu2ZnSn(S,Se)4) absorbers are advantageous for lowing the cost, but the development of solar cells based on flexible substrates has been relatively unexplored. In this work, a flexible CZTSSe solar cell applying the Mo foil substrate was developed. The characteristics of solar cells were examined by applying the sputtering process for four precursor stacking orders (Cu/Sn/Zn/Mo foil, Cu/Zn/Sn/Mo foil, Zn/Sn/Cu/Mo foil, and Sn/Cu/Zn/Mo foil). In addition, NaF was deposited on the Mo foil, and the effects of Na were investigated. The samples were characterized by means of scanning transmission electron microscopy-energy dispersive spectrometry (STEM-EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD), a solar simulator, external quantum efficiency (EQE) measurements, depth resolved Raman spectroscopy, and admittance spectroscopy (AS).
Acknowledge: This work was supported by by the DGIST R&D Program of the Ministry of Science and ICT (18-BD-05) and the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy(MOTIE) of the Republic of Korea (No. 20173010012980).