High photo-conversion efficiency in double-graded Cu(In,Ga)(S,Se)2 thin film solar cells with two-step sulfurization post-treatment
- 주제(키워드) Bandgap grading , CIGSSe solar cell , Kelvin probe force microscopy , Raman scattering spectroscopy
- 등재 SCIE, SCOPUS
- 발행기관 John Wiley and Sons Ltd
- 발행년도 2016
- 총서유형 Journal
- URI http://www.dcollection.net/handler/ewha/000000139548
- 본문언어 영어
- Published As http://dx.doi.org/10.1002/pip.2833
- 저작권 이화여자대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
Sulfur is extensively used to increase the bandgap of Cu(In,Ga)(S,Se)2 (CIGSSe) solar cells and to improve the open circuit voltage (VOC) in order to optimize the characteristics of the devices. This study uses a sulfurization process to obtain a double-graded bandgap profile. Selenization was carried out on Cu(In,Ga) precursors, followed by one sulfurization process or two consecutive sulfurization processes on top of the CIGSe absorber layer surface. The optimum two-step sulfurization process provides an increase of VOC of 0.05V and an improvement of conversion efficiency of 1.17%. The efficiency of the 30×30cm2 monolithic module, which has 64 CIGS cells connected in series (aperture area: 878.6cm2), is 15.85%. The optical and electrical properties of the phase and the work function distribution were investigated using the depth profiles of the absorber layer as a function of the sulfurization conditions. The CIGSSe thin film formed by two-step sulfurization with a high sulfur concentration exhibits a single work function peak, better crystallinity, and higher conversion efficiency than those of the thin film formed by two-step sulfurization at low sulfur concentration. In terms of the Raman spectra depth profile, the phase areas for the CIGSSe thin film that underwent the optimized high sulfur concentration two-step-sulfurization appeared to have less of Cu2-xSe phase than that with low sulfur concentration. Consequently, surface and interface phase analysis is an essential consideration to improve cell efficiency. © 2016 John Wiley & Sons, Ltd.
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