The Application of Heterostructured SrTiO3-TiO2 Nanotube Arrays in Dye-Sensitized Solar Cells

Abstract

Heterostructured SrTiO3-TiO2 nanotube arrays (ST-TNTAs) on fluoride doped SnO2 conductive glass (FTO) were synthesized through a three-step in-situ hydrothermal reaction. TiO2 nanotubes in ST-TNTAs vertically grew on the FTO substrate in single crystallized rutile phase, while SrTiO3 grains in cubic perovskite phase dispersed evenly on the surface of TiO2. The sandwich shaped all-solid-state dye-sensitized solar cells (DSSCs) were assembled with TiO2 nanorods, nanotubes and ST-TNTAs as the photoanode, respectively. Once SrTiO3 deposited, the position of Fermi level of the composited semiconductor raised, resulting in the increase of open circuit voltage (VOC). Meanwhile, both short-circuit current density (JSC) and photoelectrical conversion efficiency (η) increased first and then decreased with the amount of SrTiO3. In comparison to TiO2 nanorods and nanotubes, ST-TNTAs demonstrated the highest photoelectrical conversion efficiency (5.42%) under the irradiation of solar simulator and external quantum efficiency (EQE) at visible region, and also the lowest electron transfer resistance, which further proved that SrTiO3 acted as a good medium for electron transfer between TiO2 and photosensitizer. As a result, both the increased surface area of the nanotube relative to the nanorod and the matched bandgap structure in the composited structure of TiO2 and SrTiO3 improve the performance of the DSSCs.