Gallium-doped magnesium zinc oxide (GMZO) transparent conducting oxide layers for CdTe thin-film photovoltaics

Zinc oxide-based TCO films have high mobility and transmission, but are limited by a bandgap of approximately 3.5 eV. High-efficiency CdTe thin-film solar cells often use window layers which are transparent over the entire spectrum. In these cells, TCO absorption can be a significant source of current loss. Relative to ZnO, MgxZn1-xO (MZO) has a higher optical bandgap and and a lower electron affinity, both of which are desirable for the front contact. MZO doped with gallium showed high conductivity and transmission over a broad range, indicating that it is suitable for high-performance CdTe thin-film solar cells. Window layer band alignment and device results are presented.