Facile Bioanchoring Strategy for the Preparation of Hierarchical Multiple Structured ZnO Crystals and Its Application as a Photoanode in Dye Sensitized Solar Cells

This paper demonstrates a facile bioanchoring strategy for controlling the crystal growth process of ZnO crystals during calcination to form hierarchical multiple structures. Crystalline phase and morphology of ZnO was investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. Results revealed the evolution of ZnO nanocrystallites from nanosize to hierarchical self-assembly of polydispersed microstructures of bars/sheets/spheres/hollow spheres in wurzite hexagonal phase. ZnO exhibited photoluminescence attributed to the presence of various defects which was further supported by Raman spectroscopy and energy-dispersive X-ray spectroscopy. On the basis of the various experimental results, a plausible growth mechanism for the formation of multiple structures of ZnO crystals is proposed. Further demonstrated is the application of the polydispersed submicrometer sized ZnO crystals as photoanode in dye sensitized solar cells for improving the power conversion efficiency (∼5.3%) through high dye loading and enhanced light absorption edge via inherent light reflection mechanism