Properties of double-layered Ga-doped Al-zinc-oxide/titanium-doped indium-tin-oxide thin films prepared by dc magnetron sputtering applied for Si-based thin film solar cells

In this article, Ga-doped Al-zinc-oxide (GAZO)/titanium-doped indium-tin-oxide (ITIO) bi-layer films were deposited onto glass substrates by direct current (dc) magnetron sputtering. The bottom ITIO film, with a thickness of 200 nm, was sputtered onto the glass substrate. The ITIO film was post-annealed at 350 degrees C for 10-120 min as a seed layer. The effect of post-annealing conditions on the morphologies, electrical, and optical properties of ITIO films was investigated. A GAZO layer with a thickness of 1200 nm was continuously sputtered onto the ITIO bottom layer. The results show that the properties of the GAZO/ITIO films were strongly dependent on the post-annealed conditions. The spectral haze (T-diffuse/T-total) of the GAZO/ITIO bi-layer films increases upon increasing the post-annealing time. The haze and resistivity of the GAZO/ITIO bi-layer films were improved with the post-annealed process. After optimizing the deposition and annealing parameters, the GAZO/ITIO bilayer film has an average transmittance of 83.20% at the 400-800 nm wavelengths, a maximum haze of 16%, and the lowest resistivity of 1.04 x 10(-3) Omega cm. Finally, the GAZO/ITIO bi-layer films, as a front electrode for silicon-based thin film solar cells, obtained a maximum efficiency of 7.10%. These encouraging experimental results have potential applications in GAZO/ITIO bi-layer film deposition by in-line sputtering without the wet-etching process and enable the production of highly efficient, low-cost thin film solar cells. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3651099]