Coevaporated Cd1-xMgxTe thin films for CdTe solar cells. (January 2020)

• Record Type: Journal Article
• Authors: Feng, Ye; Wang, Taowen; Yu, Mingzhe; Huang, Jian; Li, Wei; Hao, Xia; Zhang, Jingquan; Wu, Lili
• Is Part Of: Renewable energy. Volume 145(2020)
• Page Start: 13
• Page End: 20
• Publication Date: 2020-01
• Subjects: Cd1-xMgxTe -- Electron reflector -- Interface recombination -- CdTe solar cell; Renewable energy sources -- Periodicals; Power resources -- Periodicals; Énergies renouvelables -- Périodiques; Ressources énergétiques -- Périodiques; 333.794
• DOI: 10.1016/j.renene.2019.05.139
• Languages: English
• ISSNs: 0960-1481

Abstract

Abstract: Substantial improvement of the open-circuit voltage of thin film solar cells has been investigated by applying an electron reflector strategy. Cd1- x Mg x Te has a strong potential as an electron reflector to keep minority carriers away from the CdTe back surface to reduce the back surface recombination. In this paper, SCAPS simulations were first used to investigate device performance for CdTe solar cells with the electron reflector layers. The theoretical results indicate that the ∼0.4 eV electron barrier height for CdTe solar cells with Cd1- x Mg x Te ( E g ∼1.85 eV) is sufficient to decrease the back surface recombination and improve device performance, especially the open-circuit voltage. Thus the variation of energy gap of the Cd1- x Mg x Te thin films prepared by coevaporation as a function of x was investigated from the transmittance spectra. Then Cd1- x Mg x Te ( x ∼0.3) thin films were used as the electron reflectors for the CdTe thin film solar cells. It is found that CdTe solar cells with Cd1-x Mgx Te yielded open-circuit voltage of 804 mV and fill factor more than 70% after an 425 °C anneal, which is higher than those without Cd1- x Mg x Te. The electron reflector in CdTe solar cells can effectively reduce the carrier surface recombination, thereby resulting in the increase of the fill factor and the open-circuit voltage. Graphical abstract: The wide bandgap material, CMT with a negligible valence band offset to CdTe, was proposed to be inserted prior to the back contact to reduce the recombination of the photo-generated carriers by reflecting them back to the main junction. Significant improvements in cell performance have been achieved for CdTe solar cells.Image 10816 Highlights: SCAPS simulations were used to investigate device performance for CdTe solar cells with an electron reflector layer. The ∼0.4 eV barrier height for CdTe solar cells with CMT (∼1.85 eV) is sufficient to decrease the back surface recombination. CMT thin films were prepared by vacuum coevaporation. Significant enhancements in open-circuit voltage and fill factor for CdTe solar cells were achieved. Enhanced device performance is ascribed to the introduction of an electron reflector structure.