Synthesis and characterization of Cu₂Sn_1−xGe_xS₃

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.

Fabrication of solar cells using Ge–Sn–S thin film prepared by co-evaporation

“…In fact, in a similar chalcogen compound, Cu 2 (Sn, Ge)S 3 , the same process has been reported to shift Raman peaks to higher frequencies. 28) This further supports the idea that, in our study, part of Sn was substituted with Ge to form Ge x Sn 1−x S. In addition, since no peaks attributed to GeS 29) were observed in the Raman spectra, it can be concluded that no segregation of GeS occurred near the surface.…”

Impact of Ball Milling on the Hydrogen Evolution Performance of Cu2Sn0.38Ge0.62S3 Photocatalytic Particles Synthesized via a Flux Method

“…However, the surface Cu concentrations of the as-prepared specimens were significantly lower than would be expected regardless of the synthesis route. This surface Cu deficiency suggested the segregation of Cu-deficient secondary phases such as Cu 2 Sn 3 S 7 29,39 at the surface, as was reported in a previous paper. 6 Cu-deficient surface layers such as this have been demonstrated to improve the photovoltaic performances of Cu chalcogenides 40−42 and so would also be expected to have positive effects in the present photocathode system as well, rather than unfavorable factors such as the formation of recombination centers.…”

Fabrication of a Cu2Sn1-xGexS3thin film by the sol-gel sulfurization method

“…Reported band gap energy of CTGS is higher than that of CTS. 9,15) However, the estimated band gap energies are equal or less than that of CTS. The estimated lower band gap energy is considered to be due to the absorption of the graphite-rich layer.…”

“…From the peak shift of 0.44 deg, the chemical composition ratio of Ge/(Sn+Ge) is estimated as 0.57. 9,14) 3.2. SEM and EPMA Figures 2(a) and 2(b) show a cross-sectional SEM image and a surface SEM image of the sulfurized sample at 600 °C, respectively.…”

“…Araki et al fabricated Cu 2 Sn 1-x Ge x S 3 (CTGS) samples by a solid state reaction. 9) Peaks of X-ray diffraction (XRD) were shifted with x and the XRD peaks of x = 0 and x = 1 were monoclinic CTS and monoclinic Cu 2 GeS 3 (CGS), respectively. Band gap energy estimated from diffused reflectance spectra was varied from 0.86 to 1.53 eV with increasing of x from 0 to 1.…”