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http://dx.doi.org/10.21218/CPR.2019.7.1.001

Preparation of a Dense Cu(In,Ga)Se2 Film From (In,Se)/(Cu,Ga) Stacked Precursor for CIGS Solar Cells  

Mun, Seon Hong (Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology)
Chalapathy, R.B.V. (Department of Physics, Vel Tech High Tech Dr Rangarajan Dr Sakunthla Engineering College)
Ahn, Jin Hyung (R&D Division, Hyundai Heavy Industries Green Energy)
Park, Jung Woo (R&D Division, Hyundai Heavy Industries Green Energy)
Kim, Ki Hwan (Photovoltaic Team, Korea Institute of Energy Research)
Yun, Jae Ho (Photovoltaic Team, Korea Institute of Energy Research)
Ahn, Byung Tae (Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology)
Publication Information
Current Photovoltaic Research / v.7, no.1, 2019 , pp. 1-8 More about this Journal
Abstract
The $Cu(In,Ga)Se_2$ (CIGS) thin film obtained by two-step process (metal deposition and Se annealing) has a rough surface morphology and many voids at the CIGS/Mo interface. To solve the problem a precursor that contains Se was employer by depositing a (In,Se)/(Cu,Ga) stacked layer. We devised a two-step annealing (vacuum pre-annealing and Se annealing) for the precursor because direct annealing of the precursor in Se environment resulted in the small grains with unwanted demarcation between stacked layers. After vacuum pre-annealing up to $500^{\circ}C$ the CIGS film consisted of CIGS phase and secondary phases including $In_4Se_3$, InSe, and $Cu_9(In,Ga)_4$. The secondary phases were completely converted to CIGS phase by a subsequent Se annealing. A void-free CIGS/Mo interface was obtained by the two-step annealing process. Especially, the CIGS film prepared by vacuum annealing $450^{\circ}C$ and subsequent Se annealing $550^{\circ}C$ showed a densely-packed grains with smooth surface, well-aligned bamboo grains on the top of the film, little voids in the film, and also little voids at the CIGS/Mo interface. The smooth surface enhanced the cell performance due to the increase of shunt resistance.
Keywords
CIGS solar cell; (In,Se)/(Cu,Ga) precursor; Vacuum pre-annealing and selenization; Dense CIGS film; Smooth surface;
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