The diffusion of S in the CdTe layer of a CdS/CdTe solar cell was simulated by using a finite difference algorithm which assumed the existence of a columnar grain structure; as approximated by a cylindrical grain. This differed from previous studies by the inclusion of a so-called dynamic diffusant source rather than the usual constant infinite source. The simulations revealed a rapid diffusion into the grain boundary, as compared with the bulk of the grain. It was also shown that the grain-boundary diffusion could be limited by the rate at which diffusant was supplied to the grain boundary; that is, by the mobility of S in CdS.

Sulphur Diffusion in Cadmium Telluride Thin Films Part 2 - Modelling Grain-Boundary Diffusion. M.A.Cousins, D.W.Lane, K.D.Rogers: Thin Solid Films, 2003, 431-432, 78-83