Fabrication of SrTiO3–TiO2 heterojunction photoanode with enlarged pore diameter for dye-sensitized solar cells

Abstract

We have demonstrated the N719 dye-SrTiO3–TiO2 system for the application in dye-sensitized solar cells, which is thermodynamically more favorable for electron transport and charge separation efficiency. The heterojunction SrTiO3–TiO2 photoanode with an enlarged pore diameter was fabricated by anodization of a Ti foil substrate and sequential hydrothermal reaction. Their photoelectrochemical properties were investigated as dye-sensitized solar cells for the first time. The optimal conditions for enlarged pore diameter of anodized TiO2 nanotube arrays (TNTAs) were suggested using a tetraethylene glycol based electrolyte, and SrTiO3 for the heterojunction photoanode was hydrothermally reacted on TNTAs. The structure and pore size of the hetero-structured SrTiO3–TiO2 nanotubes arrays (ST-TNTAs) were studied comparatively for their photocatalytic activity in parallel with various SrTiO3 morphologies. The enhanced photocatalytic property of ST-TNTAs compared with TNTAs could be attributed to the enhanced suppression of charge recombination by the heterojunction of ST-TNTAs due to easier crossing of the interface of ST-TNTAs by more the negative conduction band potential of SrTiO3. This is also possible because of the optimized interfacial area and the distance between SrTiO3 nanoparticles and TNTAs. With electrochemical impedance spectroscopy, we report promising applications of dye-sensitized solar cells with the hetero-structured photoanode of ST-TNTAs for the first time.