RECRYSTALLIZATION AND SULFUR DIFFUSION IN CDCL2-TREATED CDTE CDS THIN-FILMS/

The role of CdCl2 in prompting recrystallization, grain growth and int erdiffusion between CdS and CdTe layers irt physical vapor-deposited C dS/CdTe thin-film solar cells is presented, Several CdTe/CdS thin-film samples with different CdTe flint thicknesses were treated in air at 415 degrees C for differ ent times with and without a surface canting of CdCl2. The samples were characterized by scanning electron microsco py, transmission electron microscopy, energy dispersive x-ray spectros copy, x-ray diffractometry and optical absorption. The results show th at CdCl2 treatment enhances the recrystallization and diffusion pl pro cesses, leading to a compositional variation within the CdTe layer due to diffusion of sulfur from the CdS, The highest sulfur concentration s observed after 30 min treatments with CdCl2 at 415 degrees C are nea r the solubility limit for sulfur in CdTe, The compositional distribut ions indicated by x-ray diffraction measurements of samples with diffe rent CdTe thickness show that the S-rich CdTe1-xSx region lies near th e CdTe/CdS interface, A multiple-step mixing process mast be inferred to account for the diffraction profiles obtained. (C) 1997 John Wiley & Sons, Ltd.