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

Abstract

In this study, we produced thin-film solar cells using co-evaporated Ge-Sn-S thin film as the light-absorbing layer. The thin films were prepared at different concentrations of Ge and substrate temperatures. We characterized the solar cells and compared their physical properties with that of an SnS thin film fabricated using only Sn and S. The GexSn1-xS (x = 0.27) thin film solar cell exhibited the best performance, with short circuit current density Jsc = 0.66 mA/cm2, curve factor FF = 0.324, power conversion efficiency PCE = 0.036%, and open circuit voltage Voc = 0.169 V. The band gap of the GexSn1-xS (x = 0.27) thin film estimated by extrapolating the absorption edge of the external quantum efficiency was 1.57 eV, which is larger than that of the SnS thin film. This suggests that Sn (in SnS) is partially replaced by Ge to form a solid solution, thus widening the band gap.

Fabrication of (Ge0.42Sn0.58)S Thin Films via Co-Evaporation and Their Solar Cell Applications

“…However, there have been very few reports on fabricating (Ge, Sn)S thin films; therefore, this topic requires further investigation. A previous study reported the fabrication of (Ge x Sn 1−x )S (x = 0.18, 0.27) thin films via co-evaporation and their application in thin-film solar cells [32]. Our study reports the fabrication and solar cell applications of (Ge x Sn 1−x )S thin films containing more Ge than previously reported.…”

“…No peaks a ributable to GeS and SnS2 were observed [36,37]. A higher-wavenumber peak shift was observed in the (Ge0.42 Sn0.58)S spec- Figure 3 shows the Raman spectra of the SnS [32] and (Ge 0.42 Sn 0.58 )S thin films. The spectral peaks of the SnS thin film could be attributed to orthorhombic SnS; peaks were observed at 95.9 cm −1 (A g ), 164.0 cm −1 (B 3g ), 192.0 cm −1 (A g ), and 219.5 cm −1 (A g ) (the vibrational modes are indicated in brackets) [35].…”

“…Moreover, as shown in Figure 2a, a peak at 12.90° (possibly due to Sn2S3) was observed in the XRD spectrum of the (Ge0.42 Sn0.58)S thin film; here, the peak appeared at a higher angle than its position in the reference (Sn2S3 #00-014-0619) spectrum, probably because a part of Sn2S3 was substituted by Ge to form (Ge, Sn)2S3. Figure 3 shows the Raman spectra of the SnS [32] and (Ge0.42 Sn0.58)S thin films. The spectral peaks of the SnS thin film could be a ributed to orthorhombic SnS; peaks were observed at 95.9 cm −1 (Ag), 164.0 cm −1 (B3g), 192.0 cm −1 (Ag), and 219.5 cm −1 (Ag) (the vibrational modes are indicated in brackets) [35].…”

“…Raman spectroscopy did not indicate any of the different phases (such as GeS 2 or Sn 2 S 3 ) indicated by XRD analysis; thus, it is suggested that (Ge, Sn)S predominantly existed near the surface of the (Ge 0.42 Sn 0.58 )S thin film. Figure 3 shows the Raman spectra of the SnS [32] and (Ge0.42 Sn0.58)S thin films. The spectral peaks of the SnS thin film could be a ributed to orthorhombic SnS; peaks were observed at 95.9 cm −1 (Ag), 164.0 cm −1 (B3g), 192.0 cm −1 (Ag), and 219.5 cm −1 (Ag) (the vibrational modes are indicated in brackets) [35].…”

“…Our study reports the fabrication and solar cell applications of (Ge x Sn 1−x )S thin films containing more Ge than previously reported. We then discuss the Ge solid solution effect by comparing it with the SnS we fabricated in the past [32].…”