Understanding copper diffusion in CuInSe2 with first-principles based atomistic and continuum models

We investigate the diffusion of copper in CuInSe 2 using thermodynamic and kinetic models based on density functional theory calculations, attempting to reconcile large differences in reported experimental diffusivities. We find that observations of rapid chemical diffusion can be explained by large thermodynamic factors, which we calculate using a compositionally constrained model of intrinsic point defect formation. We further characterize how copper diffusion coefficients depend on material synthesis conditions and exhibit their variation across the CuInSe 2 secondary phase diagram. In doing so, we identify stable off-stoichiometries that are dominated by either vacancy- or interstitial-mediated diffusion mechanisms. These results are employed in the development of a continuum reaction-diffusion model, which we use to simulate experimental depth profiles.

Automated summary

The diffusion of copper in CuInSe2 was investigated using thermodynamic and kinetic models based on density functional theory calculations. Stable off-stoichiometries dominated by either vacancy- or interstitial-mediated diffusion mechanisms were identified. The findings were used to develop a continuum reaction-diffusion model for simulating experimental depth profiles.