High surface area electrospun prickle-like hierarchical anatase TiO2 nanofibers for dye-sensitized solar cell photoanodes

In this study, a prickle-like hierarchical anatase TiO2 nanofiber (HTF) was synthesized via an electrospinning method followed by a template-free alkali hydrothermal process and calcination. It was found that dense nanotube prickle-like branches were grown on the HTF with a surface area of up to 154 m(2)g(-1) and this was similar to 4.3 times larger than that of the pure electrospun TiO2 nanofiber (TNF). When applied in a dye sensitized solar cell (DSSC), the highest power conversion efficiency (7.86%) was achieved using a HTF-based bi-layer device. This result was similar to 26% higher than that achieved using the TNF-based bi-layer device (6.24%). The significant improvement in DSSC efficiency was investigated using intensity-modulated photocurrent spectroscopy (IMPS), intensity-modulated photovoltage spectroscopy (IMVS) and electrochemical impedance spectroscopy (EIS) measurements. Examining the results of these measurements, we attribute the improvement to the hierarchical structure of HTF, as it results in greater dye loading and better light scattering, leading to higher light harvesting, as well as faster electron transport and less charge recombination, resulting in a higher charge collection efficiency.