In this study, as a novel approach to thin-film solar cells based on tin sulfide, an environmentally friendly material, we attempted to fabricate (Ge, Sn)S thin films for application in ...multi-junction solar cells. A (Ge
Sn
)S thin film was prepared via co-evaporation. The (Ge
Sn
)S thin film formed a (Ge, Sn)S solid solution, as confirmed by X-ray diffraction (XRD) and Raman spectroscopy analyses. The open circuit voltage (
), short circuit current density (
), fill factor (
), and power conversion efficiency (
) of (Ge
Sn
)S thin-film solar cells were 0.29 V, 6.92 mA/cm
, 0.34, and 0.67%, respectively; moreover, the device showed a band gap of 1.42-1.52 eV. We showed that solar cells can be realized even in a composition range with a relatively higher Ge concentration than the (Ge, Sn)S solar cells reported to date. This result enhances the feasibility of multi-junction SnS-system thin-film solar cells.
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Cu2SnS3 (CTS), obtained by depositing Au on an Sn/Cu metal stacked precursor fabricated by electron beam deposition and sulfurization, was investigated. In thin films obtained by sulfurization at 560 ...°C of the precursor with SLG/Mo/Sn/Cu/Au/NaF structures fabricated on Soda lime glass substrates containing alkali metals, a significant increase in the CTS grain size was observed in the Au deposition thickness range of 5–25 nm. By contrast, no crystal growth was observed in thin films with a precursor without an NaF layer fabricated using alkali-free glass (EAGLE XG), regardless of the thickness of the Au-deposited film. Therefore, appropriate amounts of Au and Na promote the crystal growth of CTS. In addition, at the sulfurization temperature of 570 °C, the crystal grains were larger than those of the thin film fabricated at 560 °C. In the fabricated CTS thin-film solar cells, with a sulfurization temperature of 570 °C and an Au deposition thickness of 10 nm, open circuit voltage of 0.261 V, short circuit current density of 25.4 mA cm−2, fill factor of 0.425, and a power conversion efficiency of 2.82% were obtained.
The ternary compound Cu2SnS3 (CTS) is composed of elements that are low in cost, non‐toxic, and abundant in the Earth's crust. In addition, CTS is a p‐type semiconductor with a high reported ...absorption coefficient of more than 104 cm−1 and a band gap energy of 0.92–1.77 eV. It is, therefore, considered to be a suitable candidate for the absorber layer in thin film solar cells. In the present study, CTS thin films were produced by first depositing precursor films by co‐evaporation of Cu, Sn, and S, and then annealing them. Solar cells were then fabricated using the CTS films as absorber layers, and the dependence of their photovoltaic properties on the annealing temperature was investigated. The solar cell using the CTS thin film annealed at 570 °C exhibited an open‐circuit voltage of 248 mV, a short‐circuit current density of 33.5 mA/cm2, a fill factor of 0.439, and a conversion efficiency of 3.66%.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Temperature dependence of PL spectrum (a) Cu-poor CTS, (b) Stoichiometric CTS, (c) Cu-rich CTS, (d) Cu-poor NCTS, (e) Stoichiometric NCTS, (f) Cu-rich NCTS, where CTS and NCTS mean Cu2SnS3 and Na ...added Cu2SnS3, respectively.
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•Six types of Cu2SnS3 (CTS) and NCTS (Na doped CTS) were prepared.•DAP recombination luminescence of monoclinic Cu2SnS3 were observed.•Excition luminescence were observed in Cu-rich CTS and NCTS.•Estimated activation energy of NCTS was smaller than that of CTS.
Cu2SnS3 (CTS) solar cells, which have the highest conversion efficiency, are fabricated under Cu-poor conditions and Na addition. We investigated the contribution of these conditions to solar cell efficiency through photoluminescence observation. Samples were prepared by solid state reaction and classified into six types: Cu-poor, stoichiometric, Cu-rich, and with and without Na. The exciton luminescence was observed in both Cu-rich samples. In all samples, luminescence bands were observed at energies less than 0.9 eV, and these were determined to be donor-acceptor pair (DAP) recombination luminescence bands. The estimated activation energy of the DAP recombination luminescence of CTS was smaller with Na than without. Therefore, it is believed that the conversion efficiency improvement by Na addition is due to increased carrier density because the acceptor level approaches the valence band.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Cu2Sn1-xGexS3 (CTGS) is a compound composed of relatively abundant elements in the crust of the earth. The band gap of CTGS can be tuned by substituting elements at the Sn and Ge sites, making it an ...attractive material for low-environmental-impact solar cells. In this study, CTGS thin films were fabricated with a controlled Ge/(Ge + Sn) composition ratio (x) by combining the co-evaporation method and sulfurization in an infrared furnace. Furthermore, the effect of Na on the CTGS and changes in the solar cell properties were investigated by stacking and sulfurizing NaF on the precursor fabricated using the co-evaporation method. As a result, CTGS with varying x was successfully fabricated by varying the deposition time of the Cu2GeS3 layer using co-evaporation. Additionally, CTGS prepared by doping with Na showed enlarged CTGS crystals compared to Na-free CTGS. The fabricated CTGS solar cells achieved a power conversion efficiency of more than 4.5% after doping with Na.
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Cu2SnS3 (CTS) thin-film solar cells were fabricated by the co-evaporation of the precursors, and the effect of annealing in N2 atmosphere on their photovoltaic properties was investigated by varying ...the annealing temperature after the chemical bath deposition of CdS. The characteristics of the solar cells improved as the annealing temperature was increased in the 250 °C–275 °C range (annealing time: 30 min). However, annealing temperatures exceeding 275 °C caused the deterioration of the device characteristics. Therefore, annealing in the 250 °C–275 °C range after CdS deposition is important for forming an optimum p–n junction at the CTS/CdS interface for manufacturing the CTS solar cells evaluated in this study. The best-performing solar cell fabricated using a CTS film annealed at 275 °C after CdS deposition exhibited an open circuit voltage of 0.181 V, with a short circuit current density of 20.9 mA cm−2, fill factor of 0.462, and power conversion efficiency of 1.74%.
Temperature‐dependent optical absorption spectra from transmittance and reflectance measurements of Cu2SnS3 (CTS) thin films which are promising material for solar cells were investigated. Thin film ...CTS samples with Cu‐poor, near‐stoichiometric, and Cu‐rich compositions were prepared on glass substrates by thermal co‐evaporation and sulfurization. At low temperature, three band‐to‐band (BB) transitions that are allowed between triple upper valence bands and a single lower conduction band were observed for all samples. The square of the product of the absorption coefficient and the photon energy was plotted to estimate the band gap energy for three bands of the Cu‐poor sample. On the other hand, excitonic (EX) transitions that corresponded to three bands were observed for the Cu‐rich and near‐stoichiometric samples. Temperature‐dependent optical absorption spectra with the triple BB and EX transitions were resolved using a simplified fitting equation with Lorentzian functions as the EX transitions. The band gap, EX transition, and exciton binding energies for the lowest energy band of the Cu‐rich sample were determined to be 0.945 eV, 0.936 eV, and 8.9 meV at 6 K, respectively. In the low‐temperature region, anomalous blue‐shifts of the estimated band gap energy with increasing temperature were obtained for three bands of all samples.
Temperature‐dependent optical absorption spectra of Cu2SnS3 thin films which are promising material for solar cells were investigated. Three excitonic and band‐to‐band transitions that are allowed between triple upper valence bands and a single lower conduction band were observed. In the low‐temperature region, anomalous blue‐shifts of the band gap energy with increasing temperature were obtained for three bands.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Ag8SnS6 (ATS) has been reported to have a band gap of 1.33 eV and is expected to be a suitable material for the light-absorbing layers of compound thin-film solar cells. However, studies on solar ...cells that use ATS are currently lacking. The objective of this study is to obtain high-quality ATS thin films for the realization of compound thin-film solar cells using vacuum deposition and sulfide annealing. First, glass/SnS/Ag stacked precursors are prepared by vacuum deposition. Subsequently, they are converted to the ATS phase via sulfide annealing, and various process conditions, namely, annealing time, annealing temperature, and number of steps, are studied. By setting the heat treatment temperature at 550 °C and the heat treatment time at 60 min, a high-quality ATS thin film could be obtained. Multi-step heat treatment also produces thin films with nearly no segregation or voids.
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