The Preparation Of TiO₂/WO₃Composite Photoanode And Performance Investigation Of Dye-sensitized Solar Cells

Abstract:Dye-sensitized solar cell (DSSC) has drawn much attention on account of its low cost, simple fabrication process and potentiality of high efficiency. The semiconductor film in photoanode is vital for the photoelectric properties of DSSC, so it’s important to improve it. TiO2is the most-studied semiconductor material in DSSC for its stable performance and low cost. However, electron recombination rate is high in TiO2material, which restricts the further improvement of DSSC performance. In order to solve this problem and explore the new way to improve photoelectric properties of DSSC, good electron transporter WO3and electron acceptor phosphotungstic acid (PTA) were choosed to composite with pure TiO2to retard recombination and accelerate charge transfer.WO3and PTA-TiO2composite (PT) nanopartices were preprared through solution based method and sol-gel method, respectively. WO3and PT were added into TiO2pastes consisted of P25, DI water, dispersants, emulsifier and pore-forming agent. WO3/TiO2composite films and PTA/WO3/TiO2composite films were prepared by dotor-blading pastes onto FTO substrates and sintering subsequently. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Ultraviolet-visible absorption spectra (UV-vis) were used to investigate the as-preprared products and the influences caused by the introduction of WO3and PT. The results show that WO3particles were monoclinic, with particle size distribution35～50nm. As-preprared PT particles were anatase predominatly, with particle size distribution8～12nm. PTA was introduced into TiO2successfully. The introduction of WO3and PT didn’t affect the crystalline phase and had few influences on light absorption ablity of TiO2films.DSSCs were fabricated using pure TiO2films, WO3/TiO2composite films and PTA/WO3/TiO2composite films as working electrodes individually. The I3-/T-redox couple and Pt coated conducting glass were used as electrolyte and counter electrode, respectively. The influences on the performance of solar cell caused by the introduction of WO3and PT were studied by I-V, incident photo to current conversion efficiency (IPCE) and electrochemical impedance spectroscopy (EIS) measurements. It was found that the introduction of WO3and PT can reduce the charge transfer resistance, retard recombination and improve the conversion efficiency of DSSC. For DSSCs based on WO3/TiO2films, the best performance is Voc=0.62mV, Jsc=12.10mA/cm, η=4.65%. For the DSSCs based on PTA/WO3/TiO2films, the conversion efficiencies get higher than the DSSCs based on WO3/TiO2films and the best conversion efficiency has reached to4.94%, which is39.5%higher than the DSSCs based on pure P25films.