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To improve the quality and obtain single-phase monoclinic Cu2SnS3 (CTS) thin films, precursors, which were deposited by a non-vacuum dual-source fine-channel mist chemical vapor deposition (CVD) process, were annealed by covering them with a soda lime glass (SLG) substrate or other precursors. After annealing with a cover, the annealed precursor showed X-ray diffraction (XRD) peaks attributable only to monoclinic CTS; however, the chemical composition of the annealed precursor covered by other types of precursors deviated from the stoichiometry. The SLG substrate was found to be suitable for the cover, and the annealing temperature dependence of cover annealing on the SLG substrate was investigated. When annealing the CTS thin film at 550 °C, only a single-phase monoclinic CTS was found in the XRD and Raman measurements. The bandgap of the CTS thin film was estimated to be approximately 0.91 eV from the α h ν 2 plots. Thus, the deposition results showed that a Cu-poor CTS thin film suitable for high-efficiency solar cells can be prepared using a non-vacuum process without the sulfurization treatment. [ABSTRACT FROM AUTHOR]

Cu2SnS3 (CTS) thin films were prepared by a dual-source mist chemical vapor deposistion (CVD) method. Cu–Sn and S mist sources were prepared separately, without a vacuum apparatus or sulfurizing process to reduce cost and to prevent exfoliation of the deposited CTS thin film. The hot plate temperature was varied in the range 350–400 ℃, and CTS thin films with a suitable morphology for solar cells were produced at 370 ℃. However, the composition ratio varied significantly upstream and downstream of the mist flow. Moreover, the S/metal ratio for all obtained films was too low, as a result of a temperature drop due to the low-temperature mist flow. Therefore, the effect of reducing the lift gas flow rate for the Cu–Sn mist source on the CTS films was investigated to prevent this temperature drop. Samples fabricated with a reduced lift gas flow rate exhibited showed X-ray diffraction peaks attributed to the (200), ( 1 ¯ 31 ), ( 1 ¯ 33 ), and ( 3 ¯ 33) planes of monoclinic CTS, as well as monoclinic CTS Raman peaks. In addition, the estimated bandgap energy for the CTS thin films was 0.93–0.96 eV, which corresponds to that reported for monoclinic CTS. This indicates that the fabricated samples were monoclinic CTS deposited by dual-source fine channel mist CVD without the need for a sulfurization process. [ABSTRACT FROM AUTHOR]