Influence of the conditions of sensitization on the characteristics of p-DSCs sensitized with asymmetric squaraines

The effect of the conditions of sensitization on the photoelectrochemical performance of p-type dye-sensitized solar cells (p-DSCs) with screen-printed nickel oxide (NiO) photocathodes is analyzed. The dye-sensitizers employed in the present study are asymmetric squaraines. The conditions of sensitization differ for the relative concentration of the anti-aggregating agentCDCA(chenideoxycholic acid) with respect to the concentration of the dye-sensitizer. The co-adsorption of CDCA onto NiO electrode brings about a decrease in the surface concentration of the anchored dye as well as a blueshift of the characteristic wavelengths of optical absorption of the asymmetric squaraines considered here. Beside this, the employment of CDCA as co-adsorbent reduces the overall conversion performance of the resulting squaraine-sensitized p-DSCs with consequent diminution of the short-circuit current density. This result is ascribed to the acid action of CDCA toward the amminic nitrogen of the squaraines. Quantum efficiency spectra show that CDCA acts as a quencher of the intrinsic photoelectrochemical activity of NiO. Moreover, CDCA does not interfere with the mechanism of charge injection effectuated by the photoexcited squaraines. The photoelectrochemical impedance spectra was analyzed employing a model of equivalent circuit developed for semiconducting nanostructure electrodes

Twofold co-ordinated Ge defects induced by gamma-ray irradiation in Ge-doped SiO2.

We report an experimental study by photoluminescence, optical absorption and Electron Paramagnetic Resonance measurements on the effects of exposure of Ge-doped amorphous SiO2 to gamma ray radiation at room temperature. We have evidenced that irradiation at doses of the order of 1 MGy is able to generate Ge-related defects, recognizable from their optical properties as twofold coordinated Ge centers. Until now, such centers, responsible for photosensitivity of Ge-doped SiO2, have been induced only in synthesis procedures of materials. The found result evidences a role played by gamma radiation in generating photosensitive defects and could furnish a novel basis for photosensitive pattern writing through ionizing radiation