Porous “sponge-like” anatase TiO2 via polymer templates: synthesis, characterization, and performance as a light-scattering material
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The synthesis of porous “sponge-like” TiO2 via a polymer gel coating technique is presented. The experimental procedure involves the preparation of a gelled polymerizable microemulsion. The polymerization of the latter leads to porous poly-N-isopropylacrylamide which forms a hydrogel in the presence of water. Via solvent exchange, a suitable TiO2 precursor is infiltrated into this structure after which its in situ hydrolysis is triggered to form porous amorphous TiO2. The subsequent calcination step allows the removal of the polymer template and the transformation of amorphous TiO2 into porous, crystalline anatase with domain sizes ranging from 200 to 250 nm. As a means of verification and proof of concept, this material is tested as light-scattering layer in dye-sensitized solar cells (DSSC), and it is found that the resulting solar cell performance is comparable to commercially available TiO2. However, an increased tendency to form rutile during DSSC fabrication was noticed when compared to commercial TiO2. As there is a large potential for optimizing the synthesis, the proposed procedure is a promising route towards porous TiO2 that performs significantly better as scattering layer in light-harvesting and optical devices.