Synthesis of simple, low cost and benign sol-gel Cu2In x Zn1- x SnS4 alloy thin films: influence of different rapid thermal annealing conditions and their photovoltaic solar cells

Yingrui Sui; Yanjie Wu; Yu Zhang; Fengyou Wang; Yanbo Gao; Shiquan Lv; Zhanwu Wang; Yunfei Sun; Maobin Wei; Bin Yao; Lili Yang

doi:10.1039/c7ra12289f

Synthesis of simple, low cost and benign sol-gel Cu₂In _x Zn_{1- x} SnS₄ alloy thin films: influence of different rapid thermal annealing conditions and their photovoltaic solar cells

RSC Adv. 2018 Feb 28;8(17):9038-9048. doi: 10.1039/c7ra12289f.

Authors

Yingrui Sui¹, Yanjie Wu¹, Yu Zhang¹, Fengyou Wang¹, Yanbo Gao¹, Shiquan Lv¹, Zhanwu Wang¹, Yunfei Sun¹, Maobin Wei¹, Bin Yao², Lili Yang¹

Affiliations

¹ Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University Siping 136000 Jilin China llyang@jlnu.edu.cn +86 434 3294566 +86 434 3294566.
² State Key Laboratory of Superhard Materials and College of Physics, Jilin University Changchun 130012 P. R. China.

Abstract

Cu₂In _x Zn_1-x SnS₄ (x = 0.4) alloy thin films were synthesized on soda lime glass (SLG) substrate by a simple low-cost sol-gel method followed by a rapid annealing technique. The influence of sulfurization temperature and sulfurization time on the structure, morphology, optical and electrical properties of Cu₂In _x Zn_1-x SnS₄ thin films was investigated in detail. The XRD and Raman results indicated that the crystalline quality of the Cu₂In _x Zn_1-x SnS₄ alloy thin films was improved, accompanied by metal deficiency, particularly tin loss with increasing the sulfurization temperature and sulfurization time. From absorption spectra it is found that the band gaps of all Cu₂In _x Zn_1-x SnS₄ films are smaller than that (1.5 eV) of the pure CZTS film due to In doping, and the band gap of the Cu₂In _x Zn_1-x SnS₄ films can be tuned in the range of 1.38 to 1.19 eV by adjusting the sulfurization temperature and sulfurization time. Hall measurement results showed that all Cu₂In _x Zn_1-x SnS₄ alloy thin films showed p-type conductivity characteristics, the hole concentration decreased and the mobility increased with the increase of sulfurization temperature and sulfurization time, which is attributed to the improvement of the crystalline quality and the reduction of grain boundaries. Finally, the Cu₂In _x Zn_1-x SnS₄ film possessing the best p-type conductivity with a hole concentration of 9.06 × 10¹⁶ cm^-3 and a mobility of 3.35 cm² V^-1 s^-1 was obtained at optimized sulfurization condition of 580 °C for 60 min. The solar cell using Cu₂In _x Zn_1-x SnS₄ as the absorber obtained at the optimized sulfurization conditions of 580 °C for 60 min demonstrates a power conversion efficiency of 2.89%. We observed an increment in open circuit voltage by 90 mV. This work shows the promising role of In in overcoming the low V _oc issue in Cu-kesterite thin film solar cells.