Cu(In,Ga)Se 2 Solar Cells with Amorphous In 2 O 3 -Based Front Contact Layers

• Published in: ACS applied materials & interfaces Vol. 9; no. 35; pp. 29677 - 29686
• Main Authors: Koida, Takashi, Ueno, Yuko, Nishinaga, Jiro, Higuchi, Hirohumi, Takahashi, Hideki, Iioka, Masayuki, Shibata, Hajime, Niki, Shigeru
• Format: Journal Article
• Language: English
• Published: United States 06.09.2017
• Subjects: photovoltaic cells; photovoltaic modules; amorphous; oxide semiconductor; In2O3; chalcopyrite compound; a-IGZO; transparent conducting oxide
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.7b07092

Amorphous (a-) In O -based front contact layers composed of transparent conducting oxide (TCO) and transparent oxide semiconductor (TOS) layers were proved to be effective in enhancing the short-circuit current density (J ) of Cu(In,Ga)Se (CIGS) solar cells with a glass/Mo/CIGS/CdS/TOS/TCO structure, while maintaining high fill factor (FF) and open-circuit voltage (V ). An n-type a-In-Ga-Zn-O layer was introduced between the CdS and TCO layers. Unlike unintentionally doped ZnO broadly used as TOS layers in CIGS solar cells, the grain-boundary(GB)-free amorphous structure of the a-In-Ga-Zn-O layers allowed high electron mobility with superior control over the carrier density (N). High FF and V values were achieved in solar cells containing a-In-Ga-Zn-O layers with N values broadly ranging from 2 × 10 to 3 × 10 cm . The decrease in FF and V produced by the electronic inhomogeneity of solar cells was mitigated by controlling the series resistance within the TOS layer of CIGS solar cells. In addition, a-In O :H and a-In-Zn-O layers exhibited higher electron mobilities than the ZnO:Al layers conventionally used as TCO layers in CIGS solar cells. The In O -based layers exhibited lower free carrier absorption while maintaining similar sheet resistance than ZnO:Al. The TCO and TOS materials and their combinations did not significantly change the V of the CIGS solar cells and the mini-modules.