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
The electrical and optical properties of electron or proton-irradiated Cu2ZnSnS4 (CZTS) solar cells were investigated. The normalized efficiency of CZTS solar cells decreased when fluence was greater ...than ~1015cm−2 for electron irradiation or 1012cm−2 for proton irradiation. This tendency is quantitatively the same as that of Cu(In,Ga)Se2 (CIGS) solar cells, and better than that of Si solar cells. One of the origins of degradation is the formation of deep defects such as Cu atoms substituted at Zn sites and nonradiative recombination centers in the CZTS layer, as suggested by the decreasing photoluminescence peak intensity at 1.2eV with increasing irradiation fluence. On the other hand, the solar cell performance improved in the case of a small amount of electron or proton irradiation due to the bombardment soaking effect. These results indicate that the CZTS solar cells show excellent tolerance of electron and proton radiation, similar to a CIGS solar cell.
•The degradation properties of electron or proton-irradiated CZTS solar cells are investigated.•The degradation tendency is quantitatively better than that of Si solar cells.•The solar cell performance improved in the case of a small amount of irradiation•CZTS solar cells show excellent tolerance of electron and proton radiation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Cu2SnS3 (CTS) p-type semiconductors are expected to be applied as a light absorption material for low-cost thin-film solar cells due to their advantageous physical properties. The influence of sodium ...addition to CTS thin films was investigated by comparing Na-free CTS and Na-doped CTS fabricated on alkali-free glass substrates. Grain growth for Na-free CTS, which has a Cu/Sn composition ratio of approximately 2.0, did not occur below 570 °C. In contrast, the addition of sodium to the CTS increased the grain sizes with an increase in the annealing temperature. Even with Na-free and Na-doped CTS, the grain sizes increased with a decrease in the Cu/Sn composition ratio. These results show that an excess of Sn combined with the presence of sodium accelerate the grain growth of CTS. Photovoltaic cells using the Na-doped CTS with a Cu/Sn ratio of 1.81 exhibited an open-circuit voltage of 242 mV, a short-circuit current density of 26.5 mA/cm2, a fill factor of 0.523, and a conversion efficiency of 3.35%. The cells using CTS without sodium did not exhibit good photovoltaic characteristics due to the small grain sizes.
To enlarge the bandgap of Cu2SnS3 (CTS), Ag‐incorporating CTS thin films are successfully deposited by sulfurizing Ag‐Cu‐Sn precursors featuring various Ag contents and the constant Cu/Sn ratio of ...1.75, which is the optimal value for CTS thin‐film solar cells. To control the Ag content of the films, the thickness of the Ag layers of the precursors is varied from 0 to 200 nm, which corresponds to the Ag/(Ag + Cu) ratio of the films varying from 0 to 0.32. The films featuring Ag/(Ag + Cu) ratios smaller than 0.16 are solid solutions of CTS and Ag2SnS3, that is, (Cu,Ag)2SnS3 (CATS), while the film featuring the Ag/(Ag + Cu) ratio of 0.32 appears to be a mixture of CATS and Ag‐Sn‐S related crystals, such as Ag8SnS6. The grain size and bandgap increase as the Ag/(Ag + Cu) ratio increases up to 0.16. The highest power conversion efficiency (PCE) of 3.6% is obtained for the cell featuring the Ag/(Ag + Cu) ratio of 0.08. The highest open cell voltage (VOC) for the CATS thin‐film solar cells is obtained to be 0.284 mV. However, the improvement in PCE is attributed to the increase in the short‐circuit current density and fill factor of the cell rather than the increase in VOC.
To enlarge the bandgap of Cu2SnS3 (CTS), Ag‐incorporating Cu2SnS3 thin films are deposited by sulfurizing Ag‐Cu‐Sn precursors featuring various Ag thicknesses and the constant Cu/Sn ratio of 1.75, which is the optimal ratio for CTS thin film solar cells. The highest PEC and VOC of 3.6% and 284 mV, respectively, are obtained for the cell featuring the 50 nm thick Ag layer.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Substrate-type CdTe thin-film solar cells with a carbon/CdTe/CdS/ZnO:Al/Ag structure were fabricated. For promoting the formation of the CdSxTe1-x mixed crystal layer in the CdS/CdTe interface, the ...heat treatment (a face-to-face annealing at 600 °C and the second CdCl2 treatment at 415 °C) of the CdS/CdTe:Cu structure was performed after the CdS deposition. Junction photoluminescence and the compositional depth profile revealed that the CdSxTe1-x mixed crystal layer was formed in the CdS/CdTe interface as a result of the heat treatment after the CdS deposition. The cell performance was slightly improved due to the heat treatment after the CdS deposition, but the conversion efficiency remained low (less than 2%), probably due to the decrease in the acceptor concentration in CdTe layer. For improving cell performance, Cu diffusion was performed after the heat treatment of the CdS/CdTe structure (second Cu doping), in addition to the Cu doping before the CdS deposition (first Cu doping). The conversion efficiency increased with increasing Cu concentration in the second Cu doping, and approximately 10% efficiency was achieved.
