The properties of surface textured ZnO:Al films grown in hydrogen atmosphere

2008 
ZnO is used as a transparent conducting oxide (TCO) for the front electrode in silicon thin film solar cells because of its low resistivity and high optical transmittance. Hydrogenated Al-doped zinc oxide (AZO:H) thin films were grown on glass by rf magnetron sputtering using a ceramic target (98 wt. % ZnO, 2 wt.% Al 2 O 3 ) in H 2 /Ar ambient. We changed the ratio of H 2 /(Ar+H 2 ) and the substrate temperature from RT to 250 °C. As results, a resistivity of 3.21 × 10 −4 Ω·cm was obtained at the 2% H 2 with the substrate temperature of 150□. UV-measurement showed that the optical transmission of AZO:H films was above 85% in the visible range with a widened optical band gap. After deposition, AZO:H films were etched in diluted HCl (0.5%) to investigate the variation of optical properties and surface morphology. The etched films had excellent scattering properties (spectral haze: 52%) and low reflectance. We will present results that demonstrate an improved light trapping due to the textured surface by an etching technique.
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