Light trapping by hydrothermally deposited zinc oxide nanostructures with high haze ratio

Surface morphology of the front transparent conductive oxide film is critical to achieve high short circuit current density in amorphous silicon (a-Si) thin film solar cells due to its high electrical conductivity and transparency accompanying excellent light scattering. Here, we present a low cost hydrothermal route to deposit zinc oxide nanoflowers and nanoflakes exhibiting low sheet resistance and high haze ratio for a-Si thin film solar cells. Zinc oxide nanoflowers and nanoflakes with various aspect ratios were grown on standard fluorine doped tin oxide glass by modulating growth time and hydrogen doping. Zinc oxide nanoflowers and nanoflakes exhibited superior light scattering compared to conventional zinc oxide nanostructures due to a higher surface area and displayed a higher haze ratio compared to the commercially available fluorine doped tin oxide films. Moreover, electrical conductivity and crystallinity of zinc oxide nanoflowers and nanoflakes could be enhanced by annealing in hydrogen atmosphere at 350 °C. We also observed that zinc oxide nanoflowers with high aspect ratio showed high transmittance spectra for a wider wavelength range. Therefore, we propose a low cost scale up synthesis of high haze ratio zinc oxide nanoflowers and nanoflakes for the enhanced performance of thin film solar cells.