ELECTRODEPOSITED CADMIUM ZINC-SULFIDE FILMS FOR SOLAR-CELLS

CdxZn1-xS thin films were made by cathodic electrodeposition. Film composition was altered by changing the concentration of ions in the deposition solution and by altering the deposition potential. Films with x from 1 to 0.53 were hexagonal polycrystals with grain size about 0.16-mu-m and grew with the c axis normal to the film surface. The lattice parameters varied with x. The as-deposited films had resistivities which decreased with increasing x. There was a near linear relationship between the composition of films determined from X-ray photoelectron spectroscopy and band gaps determined from transmission spectroscopy. Films with composition near Cd0.7Zn0.3S were used as a window layer in solar cells based on the n-CdxZn1-xS/p-CdTe heterojunction. The spectral dependence of the electron quantum efficiency was significantly better at energies above 2.0 eV for cells with these window layers compared with cells with CdS layers, illustrating the advantage of the window material with the larger band gap.