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Research Papers

Stable Cu-Based Back Contacts for CdTe Thin Film Photovoltaic Devices

[+] Author and Article Information
R. A. Enzenroth, K. L. Barth, W. S. Sampath, A. T. Kirkpatrick

Department of Mechanical Engineering, Materials Engineering Laboratory, Colorado State University, Fort Collins, CO 80523

V. Manivannan1

Department of Mechanical Engineering, Materials Engineering Laboratory, Colorado State University, Fort Collins, CO 80523mani@engr.colostate.edu

P. Noronha

 AVA Solar Inc., Fort Collins, CO 80523

1

Corresponding author.

J. Sol. Energy Eng 131(2), 021012 (Apr 09, 2009) (4 pages) doi:10.1115/1.3090820 History: Received August 17, 2007; Revised January 24, 2008; Published April 09, 2009

Cadmium telluride (CdTe) thin film photovoltaic devices fabricated in a-line process developed at Colorado State University (CSU) have shown stability during long-term (over a 5 year period) accelerated stress testing. These devices have a copper (Cu) containing back contact. The Cu profile as measured by secondary ion mass spectrometry characterization shows, for the maximum stressed device (23,399 h), that there is a significant (two times) change in the concentration of secondary Cu ions in the bulk of the material; however, the Cu concentration gradient at the back of the device has no significant change, and the CdS layer has no significant Cu concentration increase at open-circuit bias and 65°C temperature conditions. This indicates that with a proper CdCl2 treatment, Cu can be used to form the back contact for CdTe devices with acceptable stability. These devices have a projected field lifetime of greater than 60 years.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Initial JV characteristics of CdTe devices before stress

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Figure 2

JV characteristics of CdTe devices before and during stress. These same devices were analyzed by SIMS as shown in Fig. 3.

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Figure 3

SIMS characteristics of CdTe devices before and during stress. These same devices were analyzed for efficiency changes, as shown in Fig. 4.

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Figure 4

Efficiency change as a function of time for CdTe devices

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