Dye sensitised solar cells with nickel oxide photocathodes prepared via scalable microwave sintering

Photoactive NiO electrodes for cathodic dye-sensitized solar cells (p-DSCs) have been prepd. with thicknesses ranging between 0.4 and 3.0 μm by spray-depositing pre-formed NiO nanoparticles on fluorine-doped tin oxide coated glass substrates. The larger thicknesses were obtained in sequential sintering steps using a conventional furnace (CS) and a newly developed rapid discharge sintering method. The latter procedure is employed for the first time for the prepn. of p-DSCs. In particular, rapid discharge sintering represents a scalable procedure that is based on microwave-assisted plasma formation that allows the prodn. in series of mesoporous NiO electrodes with large surface areas for p-type cell photocathodes. Rapid discharge sintering possesses the unique feature of transmitting heat from the bulk of the system towards its outer interfaces with controlled confinement of the heating zone. The use of rapid discharge sintering results in a drastic redn. of processing times with respect to other deposition methods that involve heating/calcination steps with assocd. reduced costs in terms of energy. P1-dye sensitized NiO electrodes obtained via the rapid discharge sintering procedure have been tested in DSC devices and their performances have been analyzed and compared with those of cathodic DSCs derived from CS-deposited samples. The highest conversion efficiencies (0.12%) and incident photon-to-current conversion efficiencies (50%) were obtained with sintered NiO electrodes having thicknesses of about 1.5-2.0 μm. In all the devices, the photogenerated holes in NiO live significantly longer (τh ∼1 s) than have previously been reported for P1-sensitized NiO photocathodes. In addn., P1-sensitized sintered electrodes give rise to relatively high photovoltages (up to 135 mV) when the triiodide-iodide redox couple is used.