Effect of Cd content and sulfurization on structures and properties of Cd doped Cu2SnS3 thin films

• Published in: Journal of alloys and compounds 2017-10, Vol.721, p.92-99
• Main Authors: Jiang, Yuhong, Yao, Bin, Li, Yongfeng, Ding, Zhanhui, Xiao, Zhenyu, Yang, Gang, Liu, Ruijian, Liu, Kaisi, Sun, Yaming
• Format: Article
• Language: English
• Subjects: Band gap; Cadmium; Chemical compounds; Copper compounds; Crystal structure; Cu2CdSnS4; Cu2SnS3; Doping; Photovoltaic cells; Solar cells; Solid solutions; Solution process; Sulfurization; Thin film; Thin films
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2017.05.291

In the present work, we fabricated solid solution of Cd in the Cu2SnS3 (CTS:Cd) and Cu2CdSnS4 (CCTS) thin film by Cd doping in the Cu2SnS3 (CTS) with a simple solution approach and sulfurization process, and investigated the effects of Cd content and sulfurization on crystalline structure and quality as well as bandgap (Eg). It was found that a face-centered cubic CTS (C-CTS) film with Eg of 0.82 eV can be prepared by the solution approach. The C-CTS transformed into CTS:Cd with tetragonal structures (T-CTS:Cd) when the Cd contents are in the range of 4.18–13.38 at%, and further transform into T-CTS:Cd and CdS as the Cd content is between 13.38 and 19.57 at%. The Eg can be tuned from 0.82 to 1.26 eV by changing the Cd doping content for the as-fabricated samples. The sulfurization process made the C-CTS dissolve into C-CTS and T-CTS, and the T-CTS:Cd transformed into the CCTS in the Cd content of 7.30–13.54 at%. A single phase of CCTS film with Eg of 1.37 eV was obtained in the content of 10.18–13.54 at%. The sulfurization process can change crystalline structure, improve crystalline quality and tune band gap of the CTS and CCTS films at the same Cd doping content compared with the as-prepared films. It is believed that the single phase of C-CTS, T-CTS:Cd and CCTS films will be promising absorber materials of solar cells. The Cu-Sn-S-Cd alloy thin fims with different Cd contents were prepared by spin-coating the precursor solution with different Cd/Sn ratios (x = 0–1.5) follow by sulfurizing at 540 °C for 30 min. The bandgap of the CTS:Cd is related to the Cd doping content for the as-prepared Cu-Sn-S-Cd fims. While, the sulfurization process can change crystalline structure, improve crystalline quality and tune band gap of the CTS and CCTS films at the same Cd doping content compared with the as-prepared films. [Display omitted] •We fabricated high-quality Cu-Sn-S-Cd alloy thin fims with different Cd contents followed by sulfurization.•Discovered the relationship between level of Cd doping, structure and band gap of the CTS:Cd in the Cu-Sn-S-Cd films.•Found the effect of sulfurization on phase transition and bandgap of the T-CTS:Cd.•Optimized experimental conditions of preparation of high crystal quality CCTS film.