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Engineering    2017, Vol. 3 Issue (4) : 452 -459     DOI: 10.1016/J.ENG.2017.04.020
Research |
Review on Alkali Element Doping in Cu(In,Ga)Se2 Thin Films and Solar Cells
Yun Sun1(),Shuping Lin1,Wei Li2,Shiqing Cheng1,Yunxiang Zhang1,Yiming Liu3,Wei Liu1
1. Tianjin Key Laboratory of Thin Film Devices and Technology, College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300071, China
2. Engineering Research Center of Nano-Structured Thin Film Solar Cell, Beijing 102211, China
3. Mads Clausen Institute, University of Southern Denmark, Sønderborg 6400, Denmark
Abstract
Abstract  

This paper reviews the development history of alkali element doping on Cu(In,Ga)Se2 (CIGS) solar cells and summarizes important achievements that have been made in this field. The influences of incorporation strategies on CIGS absorbers and device performances are also reviewed. By analyzing CIGS surface structure and electronic property variation induced by alkali fluoride (NaF and KF) post-deposition treatment (PDT), we discuss and interpret the following issues: ① The delamination of CIGS thin films induced by Na incorporation facilitates CuInSe2 formation and inhibits Ga during low-temperature co-evaporation processes. ② The mechanisms of carrier density increase due to defect passivation by Na at grain boundaries and the surface. ③ A thinner buffer layer improves the short-circuit current without open-circuit voltage loss. This is attributed not only to better buffer layer coverage in the early stage of the chemical bath deposition process, but also to higher donor defect (CdCu+) density, which is transferred from the acceptor defect (VCu) and strengthens the buried homojunction. ④ The KF-PDT-induced lower valence band maximum at the absorber surface reduces the recombination at the absorber/buffer interface, which improves the open-circuit voltage and the fill factor of solar cells.

Keywords Alkali elements      Cu(In,Ga)Se2      Thin-film solar cells      Post-deposition treatment     
Corresponding Authors: Yun Sun   
Issue Date: 13 September 2017
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Yun Sun
Shuping Lin
Wei Li
Shiqing Cheng
Yunxiang Zhang
Yiming Liu
Wei Liu
Cite this article:   
Yun Sun,Shuping Lin,Wei Li, et al. Review on Alkali Element Doping in Cu(In,Ga)Se2 Thin Films and Solar Cells[J]. Engineering, 2017, 3(4): 452 -459 .
URL:  
http://engineering.org.cn/EN/10.1016/J.ENG.2017.04.020     OR     http://engineering.org.cn/EN/Y2017/V3/I4/452
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