Because of the advantages of both rapid electron transport of graphitic carbon and high catalytic performance of Fe3C nanoparticle, highly crystalline graphitic carbon (GC)/Fe3C nanocomposites have been prepared by a facile solid-state pyrolysis approach and used as counter electrode materials for high-efficiency dye-sensitized solar cells (DSSCs). The content of Fe3C in the composites can be modified by different hydrochloric acid treatment time. In comparison with pure highly crystalline GC, the DSSC based on GC/Fe3C nanocomposite with 13.5 wt % Fe3C content shows higher conversion efficiency (6.04%), which indicates a comparable performance to the Pt-based DSSC (6.4%) as well. Moreover, not only does our DSSCs have comparable performance to that of the Pt-based DSSC (6.4%), but also is more cost-effective as well. To evaluate the chemical catalysis and stability of nanocomposite counter electrodes toward I3(-) reduction and the interfacial charge transfer properties, GC/Fe3C nanocomposites have been quantitatively characterized by cyclic voltammetry, electrochemical impedance spectra, and Tafel polarization curve. All the results have revealed that the GC/Fe3C nanocomposite counter electrodes can exhibit high catalytic performance and fast interfacial electron transfer, which can be acted as a very promising and high cost-effective materital for DSSCs.
With a facile electrophoretic deposition and chemical bath process, CoS nanoparticles have been uniformly dispersed on the surface of the functionalized graphene nanosheets (FGNS). The composite was employed as a counter electrode of dye-sensitized solar cells (DSSCs), which yielded a power conversion efficiency of 5.54 %. It is found that this efficiency is higher than those of DSSCs based on the non-uniform CoS nanoparticles on FGNS (4.45 %) and built on the naked CoS nanoparticles (4.79 %). The achieved efficiency of our cost-effective DSSC is also comparable to that of noble metal Pt-based DSSC (5.90 %). Our studies have revealed that both the exceptional electrical conductivity of the FGNS and the excellent catalytic activity of the CoS nanoparticles improve the conversion efficiency of the uniformly FGNS-CoS composite counter electrode. The electrochemical impedance spectra, cyclic voltammetry, and Tafel polarization have evidenced the best catalytic activity and the fastest electron transport. Additionally, the dispersion condition of CoS nanoparticles on FGNS plays an important role for catalytic reduction of I3 (-) .
TiO 2 microspheres with a large surface area, high crystallinity, uniform nanostructure and good light scattering properties were synthesized in an acetone-phenol mixed solvent via a simple solvothermal process. X-ray diffraction patterns and electron microscopy images indicated that the prepared TiO 2 microspheres had a highly mesoporous structure and were composed of highly crystalline anatase nanoparticles. By tuning the ratio of the mixed solvent, high-quality TiO 2 microspheres were obtained with controllable surface areas of 122-168 m 2 g À1 . Then, the mesoporous anatase TiO 2 microspheres were used as the scattering layer of the photoelectrode, which is expected to produce high efficiency dye-sensitized solar cells (DSSCs). Compared with photoelectrodes with pure TiO 2 nanoparticles or mesoporous anatase TiO 2 microspheres, DSSCs based on a photoelectrode with a TiO 2 nanoparticle underlayer and a microsphere scattering layer yield the highest photoelectrical conversion efficiency of 7.94%. This is because the obtained TiO 2 microspheres have a large surface area and exhibit excellent light scattering, allowing for fast interfacial charge transfer, low series resistance, and superior charge collection efficiency. This has been systematically observed by the electrochemical impedance spectroscopy, intensity-modulated photocurrent spectroscopy and intensity-modulated photovoltage spectroscopy.
Herein, with the purpose of improving the efficiency of p-type dye-sensitized solar cells (DSSCs), a new layered photocathode (LP) is fabricated from irregular overlapping wrinkled porous NiO nanosheets. The LP was sensitized by using a commonly used dye, coumarin 343(C343), and then assembled into p-type DSSCs through coupling with a platinum photoanode. Photoelectochemical characterization showed that the LP cell exhibited a clearly enhanced power-conversion efficiency (by a factor of 4) compared with a cell with a NiO-nanoparticle photocathode (NP). This excellent performance could be attributed to the overlapping layered structure, which favored hole transport, as confirmed by electrochemical impedance spectroscopy, and to the large surface area of the porous NiO nanosheets, which were favorable for dye adsorption.
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