Interface morphology and phase distribution in the Cu(2-x)/CdS heterojunction - A transmission electron microscope investigation

Electron-optical techniques were applied to characterizing the structure of single crystal CuS/CdS heterojunction solar cells. An aqueous ion exchange process was used to form the Cu(2-x)S/CdS cells. Scanning the resulting cells with X-ray and TEM instruments revealed a tetragonal phase polymorph with low chalcocite. The planar intersection of the tetragonal phase and the CdS interfacial habit plane was within 30 deg of the CdS basal plane. Absorber layer low chalcocite-CdS interfaces were steeply inclined relative to the CdS basal plane. Lattice misfit, structural compatibility, and nucleation hcp-fcc transformation dislocation features which produced the planar orientations are discussed in terms of techniques for manufacturing high efficiency, extended lifetime CuS/CdS solar cells.