Enhanced solar cell performance of Cu2ZnSn(S, Se)4 thin films through structural control by using multi-metallic stacked nanolayers and fast ramping process for sulfo-selenization. (December 2016)

• Record Type: Journal Article
• Authors: Chen, Wei-Chao; Chen, Cheng-Ying; Tunuguntla, Venkatesh; Lu, Shao Hung; Su, Chaochin; Lee, Chih-Hao; Chen, Kuei-Hsien; Chen, Li-Chyong
• Is Part Of: Nano energy. Volume 30(2016:Dec.)
• Page Start: 762
• Page End: 770
• Publication Date: 2016-12
• Subjects: CZTSSe -- Thin films solar cells -- Multi-metallic stacked precursor; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2016.09.022
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: In this paper, Cu2 ZnSn(S, Se)4 (CZTSSe) thin-films were prepared by sulfo-selenization of metal precursors in H2 S environment instead of using metal selenides/sulfides as precursors. High quality CZTSSe thin films were obtained using multi-stacking metallic nanolayer precursors undergoing a fast ramping process. For the preparation of metallic stacked nanolayer precursors, we have developed a 9-layer sequential deposition of Sn/Zn/Cu metal stack onto Mo-coated soda lime glass substrate by RF-sputtering. Due to inevitable metal inter-diffusion during the sulfo-selenization, we further studied the effect of the Sn/Zn/Cu metal stacking number (therefore, the layer thickness) on the quality of thin film with respect to its device performance. In the device prepared with conventional 3-layer stack, due to insufficient inter-diffusion of precursors, excessive Cu-rich secondary phase was formed at the back contact region and resulted in poor performance of devices. By using the modified 9-layer stacked precursor and fast ramping heating process the device efficiency can be improved from 4.9% to 7.7% and open circuit voltage from 0.44 to 0.5 V. This improvement can be ascribed to a compact, smooth microstructure, presence of bronze formation and the suppression of Cu-rich bi-layer formation in the 9-layer approach. Graphical abstract: By using the modified 9-layer metal-nanostacked precursor and fast ramping heating sulfo-selenization process, the device efficiency can be significantly improved, due to homogenous crystalline phase formation and uniform grain size distribution throughout the whole metal chalcogenides thin film. Highlights: High quality Cu2 ZnSn(S, Se)4 thin films have been obtained by rapid-ramping sulfo-selenization of 9-layer stacked metallic nanolayer precursors (9LYS). Nanolayers stacking facilitate the easy inter-diffusion of metallic precursors. Uniform and homogenous grain size distribution of CZTSSe thin film is achieved. Insufficient inter-diffusion of metallic precursors and excessive Cu-rich secondary phase can be suppressed. The 9LYS-CZTSSe device exhibits a 58% enhancement in efficiency from 4.9 to 7.7%.