Electrochemical Deposition of ZnO Thin Films and Nanowires for Photovoltaic Applications

The electrochemical deposition of ZnO thin films (2D layers) and nanowires on glass substrates covered with transparent conductive oxide (TCO) was studied with the purpose to use them in nanostructured solar cells. It was shown that the bath temperature and the electrolyte concentration played an important role on the ZnO layer morphology, composition, crystallization and optical properties. It was found that the thin films deposited from electrolytes with lower potassium chloride (KCl) concentration (0.1 M) and at temperatures higher than 50°C exhibit very good optical and structural properties. The rapid thermal annealing step at 500°C improves the ZnO film properties whereas the conventional annealing did not bring a real improvement. These 2D layers could be used subsequently for the electrodeposition of ZnO nanowires which dimensions could be tailored by the seed layer (2D layer) morphology and thickness. The supporting electrolyte (KCl) concentration and the passed charge density during the electrodeposition process could be additionally used to control their dimensions. Thus grown ZnO nanowires exhibit interesting optical and structural properties and therefore could be further integrated in nanostructured extremely thin absorber (eta) and hybrid (dye sensitized or polymer) solar cells.