Development of transparent conductive oxide for thin-film silicon solar cells

Gallium-doped zinc oxide (GZO) films were deposited by DC magnetron sputtering using a GZO ceramic target at various substrate temperatures from 298 to 573 K in order to apply the films to amorphous silicon thin film solar cells. A low resistivity (∼4.28 x 10^-4 Ωcm) and a high transmittance (>90%) were obtained from the film deposited at 573 K. From X-ray diffraction, the films had columnar structures oriented along the c-axis, regardless of the substrate temperature. The lattice images and the grains were observed by using a field emission transmission electron microscope. A grain was overlapped by the crystallite of 10-15 nm, and the size of a grain was about 70 nm. Finally, the texturing conditions of the GZO films were optimized as a function of deposition temperature for potential applications to tandem solar cells and single junction amorphous silicon thin film solar cells.