Metastability and reliability of CdTe solar cells

Journal Article · Thu Mar 22 00:00:00 EDT 2018 · Journal of Physics. D, Applied Physics

DOI:https://doi.org/10.1088/1361-6463/aab1e1· OSTI ID:1592012

Guo, Da ^[1]; Brinkman, Daniel ^[2]; Shaik, Abdul R. ^[1]; Ringhofer, Christian ^[1]; Vasileska, Dragica  ^[1]

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1. Arizona State Univ., Tempe, AZ (United States)
2. San Jose State Univ., CA (United States)

Thin-film modules of all technologies often suffer from performance degradation over time. Some of the performance changes are reversible and some are not, which makes deployment, testing, and energy-yield prediction more challenging. Manufacturers devote significant empirical efforts to study these phenomena and to improve semiconductor device stability. Still, understanding the underlying reasons of these instabilities remains clouded due to the lack of ability to characterize materials at atomistic levels and the lack of interpretation from the most fundamental material science. The most commonly alleged causes of metastability in CdTe devices, such as ‘migration of Cu’, have been investigated rigorously over the past fifteen years. Still, the discussion often ended prematurely with stating observed correlations between stress conditions and changes in atomic profiles of impurities or CV doping concentration. Multiple hypotheses suggesting degradation of CdTe solar cell devices due to interaction and evolution of point defects and complexes were proposed, and none of them received strong theoretical or experimental confirmation. We believe it should be noted that atomic impurity profiles in CdTe provide very little intelligence on active doping concentrations. The same elements could form different energy states, which could be either donors or acceptors, depending on their position in crystalline lattice. Defects interact with other extrinsic and intrinsic defects; for example, changing the state of an impurity from an interstitial donor to a substitutional acceptor often is accompanied by generation of a compensating intrinsic interstitial donor defect. Moreover, all defects, intrinsic and extrinsic, interact with the electrical potential and free carriers so that charged defects may drift in the electric field and the local electrical potential affects the formation energy of the point defects. Such complexity of interactions in CdTe makes understanding of temporal changes in device performance even more challenging and a closed solution that can treat the entire system and its interactions is required.

• Research Organization: Arizona State Univ., Tempe, AZ (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
• Grant/Contract Number: EE0007536; EE0006344
• OSTI ID: 1592012
• Journal Information: Journal of Physics. D, Applied Physics, Vol. 51, Issue 15; ISSN 0022-3727
• Publisher: IOP Publishing
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
CdTe solar cells
Cu migration
diffusion–reaction modeling