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

Abstract In the present work, we fabricated solid solution of Cd in the Cu 2 SnS 3 (CTS:Cd) and Cu 2 CdSnS 4 (CCTS) thin film by Cd doping in the Cu 2 SnS 3 (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 E g 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.