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DYE SENSITISED SOLAR CELLS: NEW CHALLENGES FROM GRAPHENE CATHODE AND IODINE-FREE ELECTROLYTE
Kavan, Ladislav
Graphene nanoplatelets (GNP) in the form of thin semitransparent film on F-doped SnO2 (FTO) exhibit high electrocatalytic activity for Co(L)2; where L is 6-(lH-pyrazol-l-yl)- 2,2‘-bipyridine. GNP films with optical transmission below 88% are outperforming the activity of platinized FTO for the Co2+/3+(L)2 redox reaction. Dye-sensitized solar cells with Y123 dye adsorbed on TiO2 photoanode achieved energy conversion efficiencies between 8 to 10 % for both GNP and Pt-based cathodes. However, the cell with GNP cathode is superior to that with Pt-FTO cathode in fill factors and in the efficiency at higher illumination intensities.
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Electrochemical and spectroelectrochemical study of nanocrystalline TiO2 anatase with exposed (001) faces
Lásková, Barbora ; Zukalová, Markéta ; Bouša, Milan ; Kavan, Ladislav ; Liska, P. ; Grätzel, M.
The electrochemical and spectroelectrochemical behavior ot TiO2 anatase with a predominant (001) face was studied and compared to a reference anatase material with dominating (101) face. The electrochemical measurements indicate that Li-ion insertion/extraction is facilitated for TiO2 anatase with (001) faces as compared to (101) one. The performance of both different crystal morphologies as a photoanode material in DSC (dye sensitized solar cell) was tested too. The (001) face adsorbed smaller amount of the used dye sensitizer (C101) but provides larger open circuit voltage (Uoc) of the solar cell. The different band energetics of both particular morphologies was suggested to be the reason for the voltage enhancement of the device employing (001) anatase. To prove our hypothesis and determine their flatband potential, a spectroelectrochemical study of transparent films of nanocrystalline (001) and (101) anatase on coaducting glass was carried out. UV/Vis spectra were measured at potentials between 0 and -1.4V vs SCE and confirmed the negative shift of flatband potential for (001) anatase as compared to (101) one.
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Electrostatic assembly of alumina nanoparticles on nanocrystalline diamond films
Verveniotis, Elisseos ; Kromka, Alexander ; Rezek, Bohuslav
We apply atomic force microscope for local electrostatic charging of oxygen-terminated nanocrystalline diamond (NCD) thin films deposited on silicon, to induce electrostatically driven self-assembly of colloidal alumina nanoparticles into micro-patterns. The NCD films have sub-100 nm thickness and 60% relative sp2 phase content. We characterize charge contrast and stability in air, fluorocarbon oil and water by Kelvin force microscopy. We discuss factors influencing the charging process and demonstrate that the contrast of more than ± 1 V is needed to induce selfassembly of the nanoparticles via coulombic and polarization forces.
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