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. Hence, understanding the underlying reasons of instabilities remains clouded due to the lack of ability to characterize materials at the atomistic levels and lack of the interpretation from the most fundamental material science. The most commonly alleged causes of metastability in CdTe device, 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 concentrate-on. 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.
The goal of the proposed work is to eliminate the ambiguity between the observed performance changes under stress and their physical root cause by enabling a depth of modeling that takes account of diffusion and drift at the atomistic level coupled to the electronic subsystem responsible for a PV device’s function.
The novelty of the proposed research is that the proposed Unified Solver has the opportunity to enable improved prediction of long-term solar-cell performance as well as the separation of reversible and irreversible changes. Overall, the confidence in the prediction of thin-film module reliability has the opportunity to move away from empirical observation to scientific understanding. Based on the detailed understanding, approaches will be proposed to overcome the long-term instability of the CdTe solar cell under stress.