Photovoltaic performance improvement of dye-sensitized solar cells through introducing In-doped TiO_2 film at conducting glass and mesoporous TiO_2 interface as an efficient compact layer

摘要

In-doped TiO_2 thin film was introduced at the interface of fluorine-doped tin oxide (FTO) substrate and mesoporous TiO_2 film by spin-coating method, and its application as a new compact layer material for dye-sensitized solar cells (DSSCs) was investigated. The scanning electron microscopy (SEM), UV-visible spectroscopy, current-voltage characteristics, Mott-Schottky analysis, electrochemical impedance spectroscopy (EIS) analysis and open-circuit voltage decay (OCVD) technique are used to characterize the morphology, optical transmittance and flat-band potentials (V_(fb)) of In-doped titania compact film and its effect to the photoelectron conversion process. It was found that In-doping increased the transmittance of TiO_2 compact layer, the interfacial resistance between FTO substrate and porous TiO_2 film and the flat-band potential of TiO_2 film. The In-doped TiO_2 compact layer effectively suppressed the charge recombination from FTO to the electrolyte, increased the optical absorption of dye and then increased the short-circuit photocurrent density (J_(sc)). Furthermore, In-doped TiO_2 compact layer acted as a weak energy barrier, which increased the electron density in the mesoporous TiO_2 film, thus improved open-circuit photovoltage (V_(oc)). As a result, the overall energy conversion efficiency of the DSSC with In-doped TiO_2 compact layer was enhanced by 11.9% and 6.9% compared to the DSSC without compact layer and with pure TiO_2 compact layer, respectively. It indicated that In-doped TiO_2 is a promising compact layer material for dye-sensitized solar cells.