Growth of hierarchical TiO2 flower-like microspheres/oriented nanosheet arrays on a titanium mesh for flexible dye-sensitized solar cells

Abstract

A triple-layer TiO₂ (TiO₂-TL) structure was synthesized with an over-layer composed of TiO₂ flower-like microspheres (MSs), a middle layer of TiO₂ nanosheet arrays (NSAs) and an under-layer of TiO₂ compact film (CF) on a flexible titanium (Ti) mesh substrate using a one-step hydrothermal route followed by calcination post-treatment and used to make a series of flexible dye-sensitized solar cells (DSSCs). The dependence of the physical features (diameter and length) of this hierarchical TiO₂ structure on the NaOH concentration, temperature and hydrothermal duration is systematically studied. The fully flexible DSSCs employing such a hierarchical triple-layer TiO₂ structure as a photoanode and poly-aniline film (PANI) on the indium doped tin oxide/polyethylene naphthalate (ITO/PEN) substrate as a counter electrode exhibited a power conversion efficiency of 5.04%, which mainly benefited from the enhanced capacity for effective light scattering of MSs and fast charge transfer of NSAs.