Thermally activated resonant grating using a vanadium dioxide waveguide

International audienceIn this work, we report on the design of a one-dimensional subwavelength resonant grating comprised of a fused silica substrate and a bi-layer waveguide, consisting of a solgel synthetized anatase TiO 2 layer followed by a thin VO 2 layer that is applied using pulsed laser deposition and rapid thermal annealing. A TE waveguide mode is excited under normal incidence in the VO 2 /TiO 2 bi-layer via a positive photoresist based grating printed on top, leading to high resonant reflection at room temperature. Increasing the temperature to about 68°C causes the VO 2 to undergo a dielectric to metallic transition accompanied by optical modifications in the IR region, canceling the resonance effect. This thermally triggered absorber/emitter tunable configuration enabling the on and off switching of optical resonant excitation in a reversible manner is proposed for passive Q-switching self-protecting devices for high power lasers in the IR wavelength range. Modeling of the optimized temperature dependent resonant waveguide and preliminary experimental results are presented

3,4-Ethylenedioxythiophene-based cobalt complex: An efficient co-mediator in dye-sensitized solar cells with poly(3,4-ethylenedioxythiophene) counter-electrode

© 2015 Elsevier Ltd. All rights reserved. A mixture of Co(phen)3+/2+ and Co(EtPy)3+/2+ complexes, where EtPy is a terpyridine ligand bearing an 3,4- ethylenedioxythiophene (EDOT) substituent, has been used as redox mediator in dye-sensitized solar cells. This combination of cobalt complexes allows an electron cascade leading to enhanced cell efficiency. To explain this result, we propose a synergy between the EDOT-functionalized cobalt complex and the PEDOT counter-electrode, which favors electron transfer and reduces recombination