Swift sol–gel synthesis of mesoporous anatase-rich TiO2 aggregates via microwave and a lyophilization approach for improved light scattering in DSSCs

TiO2 aggregates (TAs) were prepared via combination of facile ‘microwave assisted sol–gel synthesis’ and ‘lyophilization based extraction.’ The rapid hydrolysis followed by peptization of titanium iso-propoxide was carried out under microwave irradiation to form TiO2 hydrosol at temperature as low as 90 °C in just 10 min. Further, lyophilization of the as-synthesized TiO2 hydrosol resulted in the formation of loosely packed TAs. The X-ray diffraction and Raman analysis confirmed the crystallinity of TAs with predominant anatase phase. The transmission electron microscopy images of TAs revealed the interlinked aggregated structure of ~10-nm-sized TiO2 nanoparticles. The scanning electron microscopy images further confirmed the agglomerated structure of TAs with the size ranging from 500 to 1000 nm, which composed of several TiO2 nanoparticles. In addition, the Brunauer–Emmett–Teller (BET) analysis of TAs revealed its mesoporous structure and high specific surface area of 95 m2/g. The photoanode films fabricated with TAs proved for its better dye intake and superior light scattering owing to its high surface area and comparable size with incident wavelength, respectively, which in turn significantly improves the light-harvesting ability. In comparison with standard P25 nanoparticle-based DSSCs, short circuit photocurrent density (J sc) and photoconversion efficiency of TA-based DSSCs showed improvement up to ~35 % under simulated AM1.5 G illumination (100 mW/cm2).