engleski

Zinc oxide for photovoltaic applications

Zinc oxide as a wide bandgap II-IV semiconductor is a promising material for many device applications such as solar cells, thin film transistors, chemical and biological sensors. For the application of ZnO as a transparent conducting electrode in solar cells it is important to develop low resistivity films with high transparency in the visible region and high stability against heat. ZnO films have a lot of advantages over widely used indium tin oxide film such as low cost, non- toxicity and high stability in atmosphere with good electrical and optical properties. The influence of preparation procedure and morphology on the electrical properties of the ZnO thin films modified by doping with aluminium were studied. The ZnO and Al doped ZnO (AZO) films were prepared on glass substrates by the sol- gel spin coating method using zinc acetate dihydrate-isopropanol- monoethanolamine sol doped with 1, 2, or 3 at % of Al with respect to Zn. The sol was aged for 24, 48, 72 h and 7 days before the spin coating process. The films were deposited 5, 10, 15, 20, 25, 30 times, with heating for 5 minutes on 150 °C between the layers. When the desired number of layers was deposited, the films were annealed at different temperatures and different heating rates to investigate the influence of the annealing process on the morphological, structural and electrical properties. The morphological, structural, electrical and optical properties of post- annealed films were investigated. For the morphological and structural characterization scanning electron microscopy (SEM) techniques, grazing incidence X-ray diffraction (XRD), Raman spectroscopy and FTIR were used. For the optical characterization, UV/VIS spectroscopy measurements of transmittance and absorbance were performed. AZO transparent conductive films with low resistivity and excellent transparency in the visible range were prepared by the sol-gel method. The fabricated films are believed to have great potential in the solar cell applications instead of the commonly used ITO and FTO substrates. Moreover, it was observed that the post- annealing temperature and rate of heating influence morphology of the AZO (Figure 1 and Figure 2). Therefore, the sol-gel procedure combined with post-annealing treatment could be also used as the new method for preparation of electron transport layers in solar cells.

zinc oxide ; sol-gel ; SEM

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