Mesoporous sub-microsphere assembly of TiO2 nanocubes with highly exposed (101) facets and improved photovoltaic performance

Abstract

In this study, TiO2 nanocubes constructed mesoporous submicrospheres (TCMS) with highly exposed {101} facets were synthesized via a facile route. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy and N2 adsorption–desorption isotherms. Field-emission scanning electron microscopy and transmission electron microscopy images indicate that TCMS with a diameter of 460 nm are assembled by interconnected 20 nm TiO2 nanocubes with exposed (101) facets. The interconnected 20 nm TiO2 nanocubes constructed ~18 nm mesopores. Raman spectroscopy shows that the intensity of the Eg (143 and 638 cm−1) peaks is much stronger than the A1g (515 cm−1) and B1g (395 cm−1) peaks for the anatase TiO2, indicating a higher percentage of exposed (101) facets. The UV–Vis spectrum shows that TCMS exhibit high scattering ability. As reflected by diffusion reflection spectra and intensity of the modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS), this hierarchical structure not only enhance light harvesting, but also facilitate electron transport and improve electron collection efficiency. When used in DSSCs, a high light-to-electricity conversion efficiency of 7.28% was achieved after introducing the TCMS as the top scattering layer, indicating a 25% increase when compared to P25 benchmark photoanode. The excellent photovoltaic performance is mainly attributed to its better light scattering and mesoporous structures in the TCMS, which contributes to higher photocurrent and photovoltaic performance.