Muli-Bath Electrodeposition of CTZS Increasing Sulfur Ratio Close to Back Contact

Abstract

Cu2(ZnSn)(S)4 (CTZS) has several good optical properties compared with other thin solid films. Producing CTZS cell layers by electrodeposition techniques is mostly attractive due to its low cost compared with other common deposition methods. According to literature review, there are serious challenges to deposit CTZS by electrochemical technique. The most challenging issue is sulfur atomic ratio which is about 50% of CTZS alloy. We introduce in this work multi-steps electrodepostion techniques on order to obtain the desired atomic composition. First step is electroplating sulfur layer on the molybdenum back contact for 5 minutes followed by CTZS low sulfur layer, the third step is electroplating sulfur again for 8 minutes, the final step is electroplating CTZS low sulfur layer for 12 minutes. Electrolyte composition of sulfur electrodeposition: was 0.085 M CuSO4 and 0.074 M Na2S2O3. Electrolyte composition of CTZS electrodeposition is similar to the previous work used in the literature 1-4. The bath composition is: 0.053 M CuSO4, 0.04 M ZnSO4, 0.086 M SnCl2, 0.075 M Na2S2O3, and 0.055 M Na2S2O3. PHydrion is used to buffer the electrolyte to pH=2, and supporting electrolyte is 0.6 M LiCl. Experiments were conducted at a rotating disk electrode in order to control and characterize the flow (Ambient temperature). The annealing post treatment is conducted on tube furnace under sulfur atmosphere for 55 minutes with no extra material addition on gas phase. Alloy surface analyses of CTZS from single bath and from multi-steps electrodeposition are in Fig. 1 and 2. The effects of both, bath composition and the electroplating time were optimized and discussed on this work. The amount of sulfur on the absorber layer was optimized by different run of multi-step electroplating technique. The alloy composition was examined using Energy-dispersive X-ray spectroscopy technique (EDS). XRD analysis method was used to characterized CTZS thickness and final crystallography. Acknowledgements Case Western Reserve University for using their instruments References [1] M. Cao, L. Li, B. L. Zhang, J. Huang, L. J. Wang, Y. Shen, Y. Sun, J. C. Jiang, G. J. Hu, Sol. Energy Mater. Sol.Cells, 93, 583 (2009). [2] Y. Lin, S. Ikeda, W. Septina, Y. Kawasaki, T. Harada, M. Matsumura, Sol. Energy Mater. Sol. Cells, 120, 218 (2014). [3] Lee SG, Kim J, Woo HS, Jo Y, Inamdar AI, et al. Current Applied Physics 14: 254-258 (2014. [4] R. Bhattacharya , J. Kim. The Open Surface Science Journal 4: 19-24 (2012). Figure 1