In this study, we prepared Ga-doped ZnO (GZO) films with qualified opto-electric properties through chemical vapor deposition of an inexpensive solution of diethylzinc in n-hexane (ca. 17 wt. %). The GZO films exhibited low resistivity (3.61 × 10−4 Ω cm) and high transmittance (85%) in the visible range. Interestingly, post-annealing treatment of the GZO films under N2 at 525 °C for just 10 min increased the number of carbon-interstitial oxygen defects (CZn + 2Oi)″, which played the role of acceptors and enhanced the film properties significantly. This approach potentially allows the fabrication of inexpensive transparent conducting oxides for use in solar cells.
We have explored the effective approach to fabricate GZO/ZnO films that can make the pyramidal surface structures of GZO films for effective light scattering by employing a low temperature ZnO buffer layer prior to high temperature GZO film growth. The GZO thin films exhibit the typical preferred growth orientations along the (002) crystallographic direction at deposition temperature of 400°C and SEM showed that column-like granule structure with planar surface was formed. In contrast, GZO films with a pyramidal texture surface were successfully developed by the control of (110) preferred orientation. We found that the light diffuse transmittance of the film with a GZO (800 nm)/ZnO (766 nm) exhibited 13% increase at 420 nm wavelength due to the formed large grain size of the pyramidal texture surface. Thus, the obtained GZO films deposited over ZnO buffer layer have high potential for use as front TCO layers in Si-based thin film solar cells. These results could develop the potential way to fabricate TCO based ZnO thin film using MOCVD or sputtering techniques by depositing a low temperature ZnO layer to serve as a template for high temperature GZO film growth. The GZO films exhibited satisfactory optoelectric properties.
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