Enhanced performance of dye-sensitized solar cells with activated carbons.

Photovoltaic performance of dye-sensitized solar cells having counter electrodes of different activated carbons (coconut shells (CC), pine trees (PN) and coals (CL)) was compared with each other and also with the performance of DSSC having conventional Pt counter electrode. The counter electrodes prepared by dispersing activated carbons in sodium carboxymethyl cellulose through grinding and subsequent ultrasonication and fabricated on fluorine doped tinoxide (FTO) glass by the D-blade method. The activated carbons showed good adhesion to substrates. The DSSCs with activated carbons counter electrodes exhibited a good light-to-electricity conversion efficiency which was also comparable with that of conventional platinum (Pt) counter electrode. The DSSCs with CC and PN activated carbon counter electrode exhibited a good performances due to their large surface area. Brunauer-Emmett-Teller (BET) values of CC and PN are 1, 111.32 m2 g(-1) and 963.03 m2 g(-1), respectively. In contrast, DSSC with the CL counter electrode showed a negative performance for its small surface area. The BET value of CL is 754.12 m2 g(-1). The good photovoltaic performances of these DSSCs were found to be related to the excellent electrochemical catalysis of the activated carbons on the redox of the iodide/tri-iodie complex, as shown by AC impedance spectroscopy.

Photoanode using hollow spherical TiO2 for duel functions in dye-sensitized solar cell.

We report a new fabrication method of a bilayer photoanode for dye sensitized solar cell having highly crystalline TiO2 with hollow spherical nanoparticles. The hollow spherical TiO2 nanoparticles in DSSC work not only as scattering layer but also as channel of electrolyte. This is due to the fact that incident light is scattered by the hollow spherical nanoparticle according to Mie theory and spherical hollow spheres allow the empty space inside each sphere to circulate the electrolyte more effectively. The nanoparticles were synthesized by hydrothermal method. The space inside the spheres was fully developed by Ostwald Ripening process and the size of hollow spheres was controlled by concentration of PVPs and hydrothermal synthesis conditions (time and temperature). The nanoparticle size and photoanode morphology of the hollow spheres were measured by scanning electron microscope (SEM). Finally, the power conversion efficiency of 6.26% has been achieved under AM 1.5G simulated sunlights (100 mW cm(-2)).

Enhanced power conversion efficiency of dye-sensitized solar cells using nanoparticle/nanotube double layered film.

To enhance the power conversion efficiency of dye-sensitized solar cell, a new type of double layered photoanode was prepared using TiO2 nanoparticle in under layer and TiO2 nanotube in upper layer. TiO2 nanotubes were synthesized by hydrothermal polymerization. The morphology and the properties were investigated and characterized by Field Emission-Scanning Electron Microscopy (FE-SEM), Field Emission-Transmission Electron Microscopy (FE-TEM), Wide Angle X-ray Diffraction (WAXD), Thermogravimetric analysis (TGA) and, Brunauer-Emmett-Teller test (BET). The light-to-electricity conversion efficiency was improved with the double-layered TiO2 film, which in turn, significantly increases the power conversion efficiency of dye-sensitized solar cells (DSSCs). This is due to large dye adsorption of light-scatters as well as TiO2 main layer. Moreover, rapid electron transport and light-havesting efficiency contributed to high conversion efficiency. The power conversion efficiency of an optimized cell (photoanode consisting of 13-15 microm main-layer and TNT over-layer) was 8.06% under simulated Air mass 1.5 (AM 1.5) global sunlight (1 Sun, 100 mW/cm2).