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Proceedings Paper

Light trapping effect from randomized textures of Ag/ZnO back reflector on hydrogenated amorphous and nanocrystalline silicon based solar cells
Author(s): Baojie Yan; Guozhen Yue; Laura Sivec; Jessica M. Owens; Ken Lord; Jeffrey Yang; Subhendu Guha; Chun-Sheng Jiang
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Paper Abstract

We report our progress in the optimization of Ag/ZnO back reflectors (BR) for a-Si:H and nc-Si:H solar cells. Theoretically, a BR with a smooth metal surface and a textured dielectric surface would be more desirable. A smooth metal/dielectric interface reduces the plasmonic resonance loss and parasitic losses due to light trapped in sharp angles; a textured dielectric/semiconductor interface provides scattering for light trapping. In order to obtain sufficient light scattering at the ZnO/silicon interface, a highly textured ZnO layer is normally used. However, a highly textured ZnO surface causes deterioration of nc-Si:H material quality. In addition, to make a highly textured ZnO surface, a thick ZnO layer is needed, which could introduce additional absorption in the bulk ZnO layer and reduce the photocurrent density. Therefore, Ag/ZnO BR structures for nc-Si:H solar cells needs to be optimized experimentally. In this study, we found that an optimized Ag/ZnO BR for nc-Si:H solar cells is constructed with textured Ag and thin ZnO layers. Although a textured Ag layer might cause certain losses resulting from plasmonic absorption, the enhanced light scattering by a moderately textured Ag layer makes it possible to use a thin ZnO layer, where the absorption in the ZnO layer is low. With such a BR, we achieved a short-circuit current density of over 29 mA/cm2 from a nc-Si:H single-junction solar cell. Using the high performance nc-Si:H cell in an a-Si:H/nc- Si:H/nc-Si:H triple-junction structure, we achieved an initial active-area efficiency of 14.5% with a total current density exceeding 30 mA/cm2.

Paper Details

Date Published: 1 September 2010
PDF: 7 pages
Proc. SPIE 7771, Thin Film Solar Technology II, 777102 (1 September 2010); doi: 10.1117/12.859867
Show Author Affiliations
Baojie Yan, United Solar Ovonic, LLC (United States)
Guozhen Yue, United Solar Ovonic, LLC (United States)
Laura Sivec, United Solar Ovonic, LLC (United States)
Jessica M. Owens, United Solar Ovonic, LLC (United States)
Ken Lord, United Solar Ovonic, LLC (United States)
Jeffrey Yang, United Solar Ovonic, LLC (United States)
Subhendu Guha, United Solar Ovonic, LLC (United States)
Chun-Sheng Jiang, National Renewable Energy Lab. (United States)

Published in SPIE Proceedings Vol. 7771:
Thin Film Solar Technology II
Alan E. Delahoy; Louay A. Eldada, Editor(s)

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