High deposition rate aluminium-doped zinc oxide films with highly efficient light trapping for silicon thin film solar cells

Aluminium-doped zinc oxide films were deposited on glass substrates at high rates by reactive mid-frequency sputtering. The in-line sputter system allows oxygen influx along the middle and sides of a dual-cathode system. The effect of varying the oxygen flow from the sides on the electrical and optical properties together with the surface morphology after wet chemical etching was investigated. Increasing the amount of oxygen flow from the sides improved the resistivity profile of static prints and gave highly conductive and transparent films in dynamic deposition mode. The etched films developed rough surface textures with effective light scattering that could be controlled by the oxygen balance between the middle and sides. Optimally textured films were used as front contacts in 1 cm(2) single junction microcrystal line solar cells yielding an initial efficiency of 8.4%. The improvement in light trapping led to short circuit densities higher than that of the reference solar cells. (C) 2007 Elsevier B.V. All rights reserved