Synthesis and characterization of Cu2Sn1−xGexS3

Abstract

Cu2SnS3 (CTS) is a promising compound for use as an absorber layer in thin‐film solar cells because it is made up of low‐cost and abundant elements. However, the band gap energy of 0.94 eV for monoclinic Cu2SnS3 is less than the optimal value for absorber layers in single‐junction solar cells. On the other hand, the band gap energy of Cu2GeS3 (CGS) is approximately 1.5–1.6 eV. Therefore, in this study, we carried out the synthesis of Cu2Sn1−xGexS3, which is a solid solution of Cu2SnS3 and Cu2GeS3. The structure of the prepared samples was investigated using X‐ray diffraction and Raman analyses. Diffuse reflectance spectra were obtained using a UV–Vis–NIR spectrometer and used to estimate the band gap energy. In X‐ray diffraction patterns from the synthesized compounds, the diffraction peaks were found to shift to higher 2θ values with increasing x, indicating a decrease in the lattice constants. In addition, the estimated band gap energy increased from 0.86 to 1.53 eV with increasing x. Cu2Sn1 − xGexS3 is, therefore, a potential candidate for use as the absorber layer in thin film solar cells because its band gap energy can be adjusted simply by varying its composition.