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Proceedings Paper

Nanophase semiconductors embedded within transparent conductive oxides matrices as optical sensitizers for photovoltaic applications
Author(s): C. G. Allen; G. H. Shih; R. J. Beal; B. G. Potter
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Paper Abstract

The optical absorption of a transparent conductive oxide (TCO), which is often used as the basis for junction or contact layers in thin film photovoltaics, can be tailored by incorporating a nanophase semiconductor (SC) component. Using a, dual-source, sequential R.F. magnetron sputter deposition technique, we manipulate the optical and electronic properties of SC:TCO composites by varying the local and extended nanophase assembly and composition. The present study explores nanocomposite systems based on Ge:ZnO and Ge:ITO. The impact of host material (ITO vs. ZnO) on the evolution of nanostructure is investigated. Heat treatment of the as-deposited films results in an increased crystallinity of the TCO and SC components, confirmed by X-ray diffraction and Raman spectroscopy studies. The presence of the SC phase is found to influence TCO grain growth and crystallographic orientation, and modification of the SC phase distribution is coincident with the morphological development of the TCO phase in both composite systems. Upon heattreatment, the high-energy optical absorption edge of the nanocomposite is blue-shifted compared to that of the corresponding as-deposited material. This indicates the development of quantum-confinement conditions for photocarriers within the Ge phase which leads to an increased energy gap over that expected for the more bulk-like, asdeposited Ge material. Under the deposition and thermal treatment conditions used in the present study, the spectral absorption response is consistent between the ZnO and ITO-based thin films examined. This suggests that carrier confinement conditions are mediated by the development of similar Ge-phase local spatial extent and Ge:TCO interfacial structures in both systems, regardless of TCO identity.

Paper Details

Date Published: 24 August 2010
PDF: 7 pages
Proc. SPIE 7772, Next Generation (Nano) Photonic and Cell Technologies for Solar Energy Conversion, 77721L (24 August 2010); doi: 10.1117/12.859875
Show Author Affiliations
C. G. Allen, The Univ. of Arizona (United States)
G. H. Shih, The Univ. of Arizona (United States)
R. J. Beal, The Univ. of Arizona (United States)
B. G. Potter, The Univ. of Arizona (United States)

Published in SPIE Proceedings Vol. 7772:
Next Generation (Nano) Photonic and Cell Technologies for Solar Energy Conversion
Loucas Tsakalakos, Editor(s)

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