Solution-processed pure Cu2ZnSnS4/CdS thin film solar cell with 7.5% efficiency

Abstract

Abstract The kesterite Cu2ZnSnS4 (CZTS) thin-film solar cell is one of the emerging solar cells. The Zn and Sn materials were prepared to substitute the rare In and Ga materials in previous CuInGaS2 cell generation. However, the secondary phase formation and the non-uniform film formation during the solution process affect deteriorating cell performance. By considering the CZTS kesterite structure, secondary phases, bandgap, and absorbance, this work aims to present the novel achievement of solution processed-pure Cu2ZnSnS4/CdS solar cell. The solar cell was made with the structure of Mo/Cu2ZnSnS4/CdS/ITO/Ag consisting of 21 subcells. The characterizations were employed through X-ray diffraction (XRD), external quantum efficiency, energy gap, and J-V curve. To the best knowledge, without further cation exchange modification and the atomic ratio of Zn/Sn = 1.26 and Cu/(Zn + Sn) = 0.86, the fabricated solar cell exhibits the novel achievement for the pure Cu2ZnSnS4/CdS standard solution process with the power conversion efficiency of 7.5% with 1.43 eV bandgap and 83.5% external quantum efficiency at 570 nm. The correlation between kesterite, secondary phases, bandgap, absorbance, dan cell performance statistics were further discussed. This work implied considering the atomic ratio of Cu-poor, Zn-rich, and the film uniformity during the spin coating process; it plays a significant role in achieving high-performance solution-processed CZTS solar cells.