Electron Lifetimes in Hierarchically Structured Photoelectrodes Biotemplated from Butterfly Wings for Dye-Sensitized Solar Cells

Hierarchical structures for TiO2 photoelectrodes, biotemplated from Parpilio paris butterfly wings, were synthesized and applied to dye-sensitized solar cells (DSSCs). The synthesized samples were characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). The adsorption kinetics of N719 dye molecules on thin TiO2 films was measured and interpreted using a pseudo-second order model. Open-circuit voltage-decay (OCVD) measurements were employed to investigate the recombination kinetics of the fine hierarchical structure. The electron lifetimes, determined by EIS, in films prepared with TiO2 nanoparticles only or with a mixture of TiO2 nanoparticles and hierarchical butterfly-wing-templated structures were respectively 6.1 and 7.4 ms, with photovoltaic conversion efficiencies of 3.48 and 4.32%, respectively. The morphology of films therefore plays an important role in their light harvesting behavior and hierachical structures lead to increased absorption.