Properties of the CdCl 2 Air-annealed CSS CdTe Thin Films

Thin 7-9μm CdTe films have been deposited on soda lime glass by close-spaced sublimation (CSS). By controlling the CSS temperature-time profile of source and substrate the pinhole-free CdTe films with a good adhesion on roughened glass were prepared. The classical solution-based CdCl2 was applied to enhance the film crystallinity and optoelectronic properties of the CdTe layers. The layers were characterized by X-ray diffraction, Raman and Photoluminescence spectroscopy, scanning microscopy (SEM), energy dispersive X-ray microanalysis and Van der Paw method. CdCl2 heat treatment is a key step in CdTe device processing. Howeverthe process leaves a significant amount of chlorine-rich residue on the CdTe surface that decreases performance of the solar cell.Annealing of the CdCl2-treated polycrystalline CdTeimproves the optoelectronic properties and thus enhances the performance of CdTe/CdS solar cells. A correlation between the structural and optoelctronic properties of CdTe layers and annealing conditions in nitrogen atmosphere at 250, 400 and 450oC for 60min of the CdCl2treated layers has been found.