Diffusion Length Studies in CuXS/CdS Solar Cells

摘要

Minority carrier diffusion lengths were determined on both sides of the Cu(x)S/CdS heterojunction in thin film polycrystalline solar cells by an Electron Beam Induced Current (EBIC) method. The experiments were performed on sections of cell exposed to the atmosphere for various lengths of time. Compositional analyses of the Cu(x)S layers of these cells were obtained by Auger Electron Spectroscopy (AES) and the texture of the underlying CdS film was found using x-ray diffraction. The electron diffusion lengths in Cu(x)S ranged from 0.11 micrometer to 0.57 micrometer. The values less than 0.2 micrometer were associated with the growth of a copper oxide layer over the Cu(x)S. The hole diffusion lengths in the CdS films ranged between 0.06 micrometer and 0.3 micrometer in the bulk and from 0.79 micrometer to very large values in the space charge layer (SCL) near the heterojunction. The films were highly textured with the (0001) direction of CdS nearly normal to the film surface. All of these results indicate that chemical and electronic inhomogeneities are not uncommon in these thin film solar cells.