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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 Cu2SnS3thin filmsare 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 VOCof 3.6% and 284 mV, respectively, are obtained for the cell featuring the 50 nm thick Ag layer.

(Cu,Ag)2SnS3thin films and solar cells are prepared by sulfurization of KF/Sn/(Cu + Ag) stacked precursors in a sulfur and tin mixing atmosphere. Their properties are investigated. Stacked KF/Sn/(Cu + Ag) precursors are deposited on Mo/soda lime glass substrate by sequential evaporation of Cu + Ag, Sn elements, and KF. The molar ratios of the evaporation materials are held constant at (Cu + Ag):Sn = 1.0:0.6 and Ag/(Cu + Ag) = 0.05, and the KF/Cu molar ratio is changed from 0 to 0.05. The precursors are crystallized by annealing for 30 min at 570 °C in a sulfur and tin mixing atmosphere. The compositions are approximately constant, and the dependence of the composition ratio on the KF addition quantity is not observed. For all samples, the X‐ray diffraction patterns and the Raman spectra corresponding to CATS are obtained. The values of Vocincreased with increasing KF/Cu molar ratio until KF/Cu = 0.03. The best solar cell in this study showed a Vocof 248 mV. (Cu,Ag)2SnS3 thin filmsare successfully fabricated by sulfurization processes of evaporated KF/Sn/(Cu+Ag) precursors in a sulfur and tin mixing atmosphere. The addition of KF to the (Cu,Ag)2SnS3 thin‐film solar cell can be considered a useful technique for the improvement of Voc, because the Vocof the samples which added KF are larger than the Vocof a KF‐free.

SnS thin films were fabricated using a co-evaporation method, and the optimization of SnS thin films in terms of substrate temperature and the dependence of their properties on Sn/S ratio were investigated. The substrate temperature was adjusted in the range of 250-350 degC. On the other hand, the SnS thin films with Sn/S compositional ratios of 0.88-1.28 were fabricated. The resulting SnS films were then used to fabricate solar cells with the structure glass/Mo/SnS/CdS/ZnO:Al/Al. It was found that the optimal substrate temperature for SnS thin films was 300 degC. The highest performance was obtained for solar cells containing a SnS thin film with a Sn/S ratio that was slightly lower than the stoichiometric value.

We investigated the effect of H2S annealing on Sb-doped Cu--In--S thin films prepared using a vacuum evaporation method. These CuInS2thin films were grown successfully when annealed above 350 °C in H2S atmosphere. It was found that the thin films were closer to stoichiometry at lower annealing temperatures compared with the undoped thin films. The carrier concentrations, resistivities and mobilities of Sb-doped thin films annealed at 400 °C were approximately $1\times 10^{18}$ cm-3, 30 $\Omega$ cm, and 1 cm2V-1s-1, respectively.

We investigated the effect of H2S annealing on Ag--In--S thin films prepared by vacuum evaporation. In thin films annealed above 350 °C, diffraction peaks except chalcopyrite AgInS2phase were not observed for a starting material ratio of 1.0 but observed for that of 1.2. Thin films annealed at 400 °C with a starting material ratio of 1.5 contained several phases. We found that the Ag/In ratios of the films could be controlled by changing the starting material ratio. Grains of films with composition ratios of 1.0 and 1.2 were nonuniform, whereas those with a composition ratio of 1.5 were uniform.