Pre-incorporation of Na into flexible Cu(In, Ga)Se2 thin film solar cells. (October 2018)

• Record Type: Journal Article
• Authors: Ma, Xuhang; Ma, Yaping; Yang, Shihang; Yang, Chunlei; Lin, Tao; Wang, Kedong; Xiao, Xudong
• Is Part Of: Solar energy. Volume 173(2018)
• Page Start: 1080
• Page End: 1086
• Publication Date: 2018-10
• Subjects: Cu(In -- Ga)Se2 -- Flexible -- Titanium -- Na doping; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2018.08.048
• Languages: English
• ISSNs: 0038-092X

Abstract

Highlights: Optimization of Na source and CIGS growth conditions in constructing flexible CIGS solar cells. NaF as Na source is better than SLGTF because of the high CIGS growth temperature. A PCE of 15.09% is achieved on flexible Ti foil. Na diffusion and Ga gradient in the absorption layer are responsible for the cell performance. Abstract: Incorporation of sodium into the Cu(In, Ga)Se2 (CIGS) absorber layer is a key step for the growth of high conversion efficiency CIGS solar cells. However, the doping of Na into CIGS layer on a flexible substrate, i.e. Titanium foil, is still a challenge. In this paper, we report our results on comparing two different Na pre-incorporation methods in constructing flexible CIGS solar cells on Ti substrates: i) by sputtering a soda-lime glass thin film (SLGTF) onto Ti substrates prior to the growth of CIGS and Mo back contact layers and ii) by evaporating a NaF precursor layer on the Mo layer before the CIGS growth. By carefully optimizing the growth conditions, the conversion efficiencies of 13.47% and 15.02% are achieved for the SLGTF sample and the NaF sample, respectively. The NaF precursor method shows a better effect. The diffusion of Na and the gradient of Ga play important roles in the performance of the solar cells.