Proceedings of 6th International Conference on Hybrid and Organic Photovoltaics (HOPV14)
Publication date: 1st March 2014
TiO2 electrodes with hierarchical porous structures (HPS) incorporating the macropores in the mesoporous materials have shown the potential to improve the efficiency of the dye-sensitized solar cell. In HPS, the macroporous channels could facilitate the infiltration of the electrolyte solution and promote mass transport, and the mesopores could provide the high surface area. In the present study, we have developed a method to prepare TiO2 film electrodes with HPS by combining the sol-gel reaction of titania precursor sol and the polymerization of organic monomer in the absence of any surfactant and colloidal templates. Firstly, the gel TiO2 film containing monomer POGTAwas irradiated with the ultraviolet light for some time. During the irradiation process, the polymerization of the photo monomer was induced, which resulted in the phase separation in the film system, one was the emerging polymer rich phase, and another was the residual monomer-TiO2 oligomer rich phase. After heat-treatment, the entire polymer decomposed and a well-defined TiO2 films with HPS could be obtained. Numerous interconnected macro/mesopores with the pore size from 30nm-1µm were embedded in the films. The photovoltaic properties of the as-prepared electrodes were optimized by varying the monomer concentration or the polymerization reaction condition. Electron transport was investigated using impedance spectroscopy. The result showed that the maximum efficiency of 5.68% was observed with the film thickness only of 3 μm. The electrodes of smaller mesopores diameters and continuous TiO2 skeleton yielded the higher photocurrent density due to the decrease in the electron transport resistance at the TiO2/dye interface. The as-prepared electrodes showed much better ionic paths for electrolyte diffusion comparing with the nanoparticles electrodes.
Fig. 1. SEM images of the films prepared with hierarchical porous structures (a) low magnification, (b) high magnification
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