CATHODIC DYE-SENSITIZED SOLAR CELLS WITH PHOTOACTIVE NIO ELECTRODES DEPOSITED VIA PLASMA-ASSISTED MICROWAVE SINTERING

The use of microwave (MW) radiation to sinter metal oxide nanoparticles in plasma atmosphere has been successfully demonstrated for the production of p-type semiconductors to be utilized as photoactive materials in cathodic dye-sensitized solar cells (p-DSCs).[1] In particular, the preparation of NiO thin films[1,2] has been realized with this innovative method. In the adopted procedure NiO nanoparticles with diameter 20-50 nm are first sprayed onto a transparent and conductive layer of fluorine-doped tin oxide, and successively sintered at about 400 °C in plasma atmosphere for less than 10 mins with MW using a characteristic frequency of 2.45 GHz.[2] NiO layers with mesoporous morphology could be obtained via MW-sintering process as demonstrated by SEM and FIB images of NiO films with thickness in the range 0.2-15 µm. The electrochemical characterization of the NiO films thus prepared was conducted in aqueous and anhydrous electrolytes. The results were compared to those obtained with samples of compact NiO having similar thickness and with nanostructured NiO films prepared with wet methods. Successively the mesoporous NiO samples were sensitized with various organic/organometallic dyes either commercial or not, and tested in sealed cells with the redox couple I2/I-. The resulting p-DSCs displayed optimum efficiencies of about 0.3 % [3] when NiO cathode had a thickness value comprised between 2 and 4 µm. Studies about the photo-electrochemical behaviour of tandem DSCs based on both MW-sintered NiO photocathodes and TiO2 photoanodes are in progress.