LiFePO_4/TiO_2/Pt composite film used as effective and robust counter electrode for dye sensitized solar cells

摘要

A series of composite films based on LiFePO_4/ TiO_2/Pt were synthesized and used as counter electrodes for dye sensitized solar cells (DSSCs). The composites are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET). These analysis results demonstrate that the crystal structure of LiFePO_4 in composite is not changed, and the prepared LiFePO_4/TiO_2/Pt composite films hold a rough surface and porous structure which provide more catalytic activity sites for I_3~- reduction and more space for I~-/I_3~- diffusion. The DSSC based on LiFePO_4/TiO_2/Pt composite CEs shows a high power conversion efficiency of 6.23% at a low Pt dosage of 2%, comparable to the conventional magnetron sputtering Pt CE (6.31%). The electrochemical analysis reveals that the presented composite CEs have good electrocatalytic activity and low charge transfer resistance. Furthermore, the DSSCs based on LiFePO_4/TiO_2/Pt composite CE exhibit high stability under the continuous tests condition and electrolyte soaking. The results suggest that this LiFePO_4-based composite film could be a perspective electrode for practical application of DSSCs and it maybe provide a potential for further research about photo-charging lithium-ion batteries.