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학술지 Reactively Sputtered Zn(O,S) Buffer Layers for Controlling Band Alignment of Cu(In,Ga)Se2 Thin-film Solar Cell Interface
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조대형, 이우정, 김명언, 김기환, 윤재호, 정용덕
Journal of Alloys and Compounds, v.842, pp.1-6
20JB1900, 무독성 버퍼층을 갖는 다색 플렉서블 박막 태양전지 기술 개발, 정용덕
© 2020 Elsevier B.V. Buffer layers in Cu(In,Ga)Se2 (CIGS) solar cells are highly preferable to be vacuum-compatible and use non-toxic materials not only for the film but also for the manufacturing process. Moreover, high controllability for the energy levels of buffer layers is greatly desirable for achieving higher solar cell efficiency because the buffer layer is formed directly onto the absorber layer which generates carriers. In this study, the S/(O + S) composition ratio of the Zn(O,S) thin films was finely controlled by varying O2/(Ar + O2) gas flow ratio using a reactive sputtering method including an Ar/O2 mixture gas and a single ZnS sputter target. The structural, electrical, and photovoltaic performance properties of the Zn(O,S) thin films and their CIGS solar cells were investigated at varied S/(O + S) composition ratios. As the S/(O + S) composition ratio of the Zn(O,S) films increased, bandgap bowing occurred with the increase of the conduction band and valence band energy levels. The photovoltaic performance was greatly influenced by the difference of the conduction band energies between the Zn(O,S) buffer and the CIGS absorber. When the conduction band energy of the Zn(O,S) was too high or too low compared to that of the CIGS, it increased the carrier recombinations or series resistance, respectively, which induced losses of the open-circuit voltage and the fill factor. The controlling and optimizing the energy levels at the Zn(O,S)/CIGS interface were crucial for improved solar cell performances.
Band alignment, Reactive sputtering, Thin-film solar cell, Zn(O,S)
KSP 제안 키워드
Augmented reality(AR), Band energy levels, Bandgap bowing, Buffer layer, CIGS absorber, CIGS solar cell, Composition ratio, Gas flow ratio, Manufacturing processes, Mixture gas, Open circuit voltage(VOC)