One-step ammoniahydrothermal synthesis of single crystal anatase TiO2nanowires for highly efficient dye-sensitized solar cells

Abstract

The single crystal anatase TiO₂ nanowires are of considerable interest for use as photoanodes in dye-sensitized solar cells (DSCs) since they can provide direct pathways for efficient charge transport and collection. The alkali hydrothermal route has been studied extensively to achieve these nanostructures, but is limited by a relatively complex procedure, requiring at least three steps including hydrothermal growth, ion exchange, and calcinations. In this study, a facile one-step ammonia hydrothermal approach was developed for the first time to grow single crystal anatase TiO₂ nanowires in the absence of exotic reagents or templates. The growth parameters such as growth time, reaction temperature, and ammonia concentration have been investigated in detail to achieve the morphology control. A growth mechanism controlled by a dissolution–recrystallization process has been proposed for formation of anatase TiO₂ nanowires. An overall power conversion efficiency of 7.10% has been achieved by using these anatase TiO₂ nanowires under simulated air mass 1.5 global sunlight, is significantly higher than that derived from P25 nanoparticles (5.57%). The electrical impedance spectroscopy analysis reveals that the great improvement in the photovoltaic performance of DSCs based on TiO₂ nanowires is mainly attributed to an effective retardation of the charge recombination and consequently enhanced electron lifetime.