Photoelectrochemical properties of mesoporous NiO x deposited on technical FTO via nanopowder sintering in conventional and plasma atmospheres

Nanoporous nickel oxide (NiOx) has been deposited with two different procedures of sintering (CS and RDS). Both samples display solid state oxidation at about 3.1 V vs Li+/Li. Upon sensitization of CS/RDS NiOx with erythrosine b (ERY), nickel oxide oxidation occurs at the same potential. Impedance spectroscopy revealed a higher charge transfer resistance for ERY-sensitized RDS NiOx with respect to sensitized CS NiOx. This was due to the chemisorption of a larger amount of ERY on RDS with respect to CS NiOx. Upon illumination the photoinduced charge transfer between ERY layer and NiOx could be observed only with oxidized CS. Photoelectrochemical effects of sensitized RDS NiOx were evidenced upon oxide reduction. With the addition of iodine RDS NiOx electrodes could give the reduction iodine → iodide in addition to the reduction of RDS NiOx. p-type dye sensitized solar cells were assembled with RDS NiOx photocathodes sensitized either by ERY or Fast Green. Resulting overall efficiencies ranged between 0.02 and 0.04 % upon irradiation with solar spectrum simulator (Iin: 0.1 W cm−2).