Synthesis and formation mechanism of mesoporous TiO2 microspheres for scattering layer in dye-sensitized solar cells

This report describes a facile method for preparing mesoporous TiO2 microspheres (TMs) for scattering layer in DSSCs. In this method, TMs can be synthesized by direct hydrolysis of TiCl4 in ethanol aqueous solution at 40 degrees C, and the microspheres size could be easily controlled by varying the adding amount of CTAB. The TMs were characterized by scanning electron microcopy (SEM), X-ray diffraction (XRD), and nitrogen sorption analysis. A possible formation mechanism of the TMs was proposed on the basis of time-dependent measurements by TEM. Photoanodes consisting of the TMs as scattering layers were then fabricated. The use of TMs largely enhances the dye loading and gives highly effective light scattering. Using TMs with a diameter of 400 nm (TM400), a high photon to electricity conversion of 9.33% has been achieved, indicating a 24% increase in the conversion efficiency compared to the photoanode without scattering layer (7.54%). The charge transport behavior of the cells was investigated by intensity-modulated photocurrent and photovoltage spectroscopic analysis (IMPS and IMVS), and the results indicates that the DSSCs with TM400 as a scattering layer has a higher eta(cc) (80.2%) value than the DSSCs without a scattering layer (71%). This method provides a feasible way for fabricating low-cost scattering layers in DSSCs. (C) 2013 Elsevier Ltd. All rights reserved.