Technical Topic Area: Topic 1 Photovoltaic Component Reliability Models In CdTe solar cells, the most commonly alleged causes of CdTe device instability, such as migration of Cu, have been interrogated 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. 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 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 defect. 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.
|Effective start/end date||9/30/13 → 6/30/17|
- DOE: Office of Energy Efficiency and Renewable Energy (EERE): $1,534,467.00
energy of formation