Deposition of large area, directly textured, ZnO:Al films by reactive-environment, hollow cathode sputtering

Aluminum-doped zinc oxide (ZnO:Al) is a promising transparent conducting oxide (TCO) for the second generation, thin film based solar cells. Moderately large area, directly textured ZnO:Al films were successfully deposited by reactive-environment, hollow cathode sputtering (RE-HCS) using metal targets. The morphology, structural, electrical, and optical properties of the films have been investigated and comparisons are made with the properties of commercially available textured SnO2:F. Higher haze and reduced absorption could be obtained with the textured ZnO:Al films. Besides the textured surface, these films (∼1030nm thick) also have a low sheet resistance of 2.8 ohms/square. Hall effect measurements on these films yielded a record high mobility of 49.5 cm²/V-s and carrier concentration of 4.42 × 10²⁰ cm⁻³. The use of these textured ZnO:Al films as a TCO for single junction a-Si cells resulted in increased Voc, Jsc, and FF. The novel deposition method of RE-HCS provides a possible and promising pathway to a relatively low cost, large area production process for a textured ZnO TCO for thin-film PV manufacturing.