Ga-doped ZnO conducting antireflection coatings for crystalline silicon solar cells

Transparent, conductive gallium-doped ZnO thin films are evaluated for application as conducting antireflection coatings (ARC) for crystalline silicon solar cells as a means to enhance efficiency by reducing the overall resistivity of the photovoltaic circuit. All Ga-doped ZnO thin films in this study were deposited using pulsed laser deposition. Synthesis conditions were first optimized for maximum electrical resistivity and minimal visible light absorption. The ideal combination contained 1 mol. % Ga doping and exhibited ∼90% transmission, with resistivity in the 1 × 10^-3 ohm-cm range. Optimized films were prepared on reference flat silicon wafers with known dopant densities and on commercially obtained solar cell emitters without ARCs. Circular transmission line method measurements were used to measure specific contact resistivity (ρ_c). For n-type doped solar cell emitters, contact resistivity values of 0.1 mΩ cm² were observed repeatedly. These values are consistent with, or lower than, contact resistivities associated with conventional silver paste metallization.