Cu migration and its impact on the metastable behavior of CdTe solar cells

In this work we report on development of a 1D reaction-diffusion simulator of Cu kinetics in CdTe solar cells to investigate its role in the observed device performance changes. Evolution of intrinsic and Cu-related defects in CdTe solar cell has been studied in time-space domain self-consistently with free carrier transport. The simulation successfully predicts decelerating reductions of device performance for open-circuit stress and steadier reductions for short-circuit stress under elevated temperature, in agreement with experimental findings. The simulation results indicate that the movement of Cu interstitials could be responsible for such changes. Although 1D simulation has intrinsic limitations when applied to polycrystalline films, the results presented here imply that the 1D approach is still suitable in better understanding of the performance and metastabilities of CdTe photovoltaic device.