High open voltage and superior light-harvesting dye-sensitized solar cells fabricated by flower-like hierarchical TiO2 composed with highly crystalline nanosheets

The morphology, microstructure and crystallography of titanium dioxide (TiO 2 ) have great effect on the photoelectric performance of dye-sensitized solar cells (DSSCs). Herein, flower-like 3D TiO 2 microstructures based on well-defined high-crystalline nanosheets are synthesized through a facile hydrothermal method . Especially, morphological evolution process and mechanism of this hierarchical structure are investigated. Due to the highly crystalline nature and smaller surface area of these nanosheets , the corresponding device shows an extremely high open-current voltage up to 0.84 V, which results from the less electron recombination. When applied as a scattering layer on top of the nanoparticle layer, the power conversion efficiency (PCE) can be significantly improved and give birth to a PCE value of 9.6%, which is 24.6% higher than that of an analogous device using nanoparticles (NP) (7.7%). As reflected by diffusion reflection spectra, intensity of the modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS) and electrochemical impedance spectra (EIS), this hierarchical structure can not only enhance light harvesting, but also reduce electron recombination, facilitate electron transport and improve electron collection efficiency.