Blue TiO2 polymorph: An efficient material for dye-sensitized solar cellsfabricated using a low-temperature sintering process

Recently, surface-disordered or non-stoichiometric TiO₂, such as blue TiO₂ (B-TiO₂), has received much attention owing to its unique properties, such as structural disorder near the surface and the existence of Ti³⁺ ions and oxygen vacancies. Therefore, surface-disordered TiO₂ has been applied for microwave absorption, photocatalysis, in photoelectrochemical sensors and rechargeable lithium-ion batteries. In this work B-TiO₂, a polymorph consisting of nanoparticles, nanotubes and nanosheets, was successfully synthesized and employed as a semiconductor layer in dye-sensitized solar cells (DSSCs) fabricated using a low-temperature heat treatment process (120?°C). Based on the analyses of the experimental results regarding the structure and those from the characterization of B-TiO₂, and its application to DSSCs, it has been found that the B-TiO₂ material has an effect on electron-hole pair separation. The conversion efficiency of the B-TiO₂ DSSC (BTiO₂-DSSC) was 6.18%, whereas that of the TiO₂-P25 DSSC (P25-DSSC) was 3.61%, and that of the TiO₂ polymorph DSSC (PTiO₂-DSSC) which is the precursor of B-TiO₂ was 4.51%.