Preparation and characterization of nanocrystalline Pt/TCG counterelectrodes for dye-sensitized solar cells

International audienceTransparent counter electrodes were prepared on transparent conductive glass (TCG) substrates from a hexachloroplatinic acid (H2PtCl6) solution applying the thermal decomposition method in combination with the spin-coating deposition technique. The effect of the precursor concentration and the number of deposited platinum layers on the surface characteristics of the Pt films was examined, and the relation between those surface characteristics and the electrochemical properties of the corresponding modified Pt/TCG electrodes was defined. Four types of counterelectrodes were prepared, differing in the concentration of the H2PtCl6 solution (0.03M and 0.15M) and in the number of Pt layers (one or two Pt layers); their performance as counterelectrodes was evaluated after their incorporation into dye-sensitized solar cells (DSSCs) employing a solid state redox electrolyte. The obtained results show that solar cells using counterelectrodes prepared from the 0.03MH2PtCl6 solution and consisting of two Pt layers (Pt032 electrode) exhibited the best performance characteristics (diffusion coefficient D*I3−=1.58×10−5cm2s−1, conversion efficiency η=2.16%, fill factor ff=62.14%, and short circuit photocurrent Isc=4.71mAcm−2). The electrochemical behavior of the modified counterelectrodes is consistent with the surface characteristics of the Pt film that formed on the conductive glass substrate, which seems to be significantly affected by the adopted method and the adjusted experimental parameters (Pt concentration and number of Pt layers). Specifically, this type of electrodes beside their low roughness (Rq=11.5nm), also presents a high complexity (Df=2.3). As a result, for this kind of solid state DSSCs, the less rough but the more complex the Pt/TCG electrode surface, the higher the efficiency of the corresponding solar cells

Nanostructured TiO2 films for DSSCS prepared by combining doctor-blade and sol-gel techniques

International audienceNanostructured TiO2 films were prepared by combining commercial titania powder (Degussa P25) with a titanium alkoxide sol. The produced composite paste was deposited on conductive glass substrates by the doctor-blade technique forming high surface area electrodes. The hydrolysis and the polymerization of the alkoxide within the clusters of the semiconductor's powder, followed by effective thermally induced sintering of the titania particles, led to nanocrystalline thin films characterized by controlled porosity, high roughness and complex surface features. The modified films were efficiently incorporated in the fabrication process of dye-sensitized solar cells (DSSCs), where an overall energy conversion efficiency (η) as high as 1.9% was achieved

Efficient photocatalysts by hydrothermal treatment of TiO2

International audienceMixed phase nanocrystalline TiO2 powders (anatase–rutile) (Degussa P25) were prepared by hydrothermal modification. The preparation procedure took place at 200 °C for 1–10 days in an autoclave system with water as the solvent. Thus, different degrees of modification were achieved. TiO2 water modified nanocrystalline thin films were immobilized on glass substrates by applying a doctor-blade's deposition technique. A variety of spectroscopic [UV–vis reflectance, infra-red (IR), Raman, structural X-ray diffraction (XRD), N2 absorption (BET)] and microscopic [atomic force microscopy (AFM), scanning electron microscopy (SEM)] techniques were applied to characterize the modified films. A model textile industry pollutant (methyl orange) was used in order to evaluate the photocatalytic efficiency of the modified material. Our results show that the photocatalytic activity of the modified films is improved by a factor of 2 when we extend the hydrothermal treatment up from 1 to about 4 days in the autoclave system. Scratch tests revealed favorable interconnection of the titania nanoparticles as well as significantly higher adhesion to the glass substrate for the modified films, in comparison to the original P25 material