Defect diffusion in CdTe and CdSe

Recent progress in the development of CdTe solar cells has involved the use of CdTe absorber layers combined with CdSe and/or CdTe_xSe_1-x layers. One area of particular interest is the interdiffusion between the CdSe layer and the CdTe layer. As a first step in understanding this, we have carried out molecular dynamics (MD) simulations of interstitial and defect diffusion in both zincblende CdTe and wurtzite CdSe over a range of temperatures using an empirical bond-order potential which has been fitted to experimental measurements and density functional theory calculations. These results were then used to determine the effective activation barriers and prefactors for Cd, Te, and Se interstitial diffusion and vacancy diffusion. Since our MD simulations reveal a wide range of different processes, including hopping and exchange, which depend on temperature and the local environment, we have also carried out additional nudged-elastic-band calculations to determine the activation energies for the key mechanisms. A summary of these results will be presented along with a discussion of their impact on the kinetics of interdiffusion between CdTe and CdSe.