Mesocrystal TiO2 films: in situ topotactic transformation and application in dye-sensitised solar cells

Abstract

Thin film ceramics and semiconductors play an important role in energy- and environment-related areas such as photovoltaics, energy storage and water purification. The morphology and structure of materials significantly affect their properties and performance in applications. Mesocrystal materials with a hierarchical structure and designable overall shape possess not only the properties from nanosized building-blocks but also collective functions from the crystallographically ordered assembly, meeting the criteria of high performance candidates in various applications. In this study, a facile and versatile method was developed to prepare mesocrystal films by simply making a printable paste of the topotactic precursor, followed by in situ topotactic transformation of printed films. Using TiO₂ as the model material, mesocrystal TiO₂ films made from NH₄TiOF₃ paste possess high surface area, crystallographic orientation of anatase nanoparticles and overall large particle size, performing well in dye-sensitised solar cells (DSSCs) as either single-layer photoanodes or additional scattering layers.