Claudia Longo

Dye sensitized TiO2 solar cells were assembled using rigid or flexible transparent electrodes (a conductive film deposited on glass or poly(ethylene terephthalate) as substrates and a polymer electrolyte based on I3-/I2 and poly(epichlorohydrin-co-ethylene oxide). The cells were characterized by current-potential curves and electrochemical impedance spectroscopy under different light intensities. Under 100 mWcm-2 illumination, the rigid cell exhibited an open circuit

ABSTRACT ZnO nanowires (NWs) grown by the hydrothermal method on fluorine-doped tin oxide glass substrate were characterized by scanning electron microscopy, optical absorption, photoelectrochemical photocurrent density, and ultrafast transient absorption pump probe spectroscopy. The as-grown NWs were annealed in air, pure hydrogen atmosphere, or annealed first with air annealing followed by hydrogen treatment. By TA spectroscopy, the samples exhibited a triple exponential transient bleach recovery with lifetimes on the fast (10–15 ps), medium (100–200 ps), and slow (>1 ns) time scale, attributed to shallow donor mixed with electron hole plasma recombination, donor bound recombination, and donor–acceptor pair recombination (DAP), respectively. The as-grown samples were dominated by donor and DAP recombination. Air annealing improved the crystal structure but had little effect on hole trapping. Significantly, the hydrogen-treated NWs showed a reduction in hole trapping and DAP recombination. Hole trapping was attributed to zinc vacancies (VZn) and hydrogen was proposed to passivate these defects. The photocurrent density of the air annealed and cotreated NWs were measured, the latter of which showed improved performance which was attributed to, in part, decreased hole trap states and improved electrical conductivity. In situ ultrafast TA spectroscopy was used to study the photoanodes under working conditions as a function of applied bias. For both samples, the medium time constant became faster with increasing applied bias. A model was proposed to extract the electron–hole separation time constant.

Alternative electrolytes for application in dye-sensitized TiO2 solar cells were investigated. The electrolytes were prepared with NaI and I2 as redox couple in a matrix consisting of poly(ethylene oxide-co-diethyleneglycolglicidyl methylether) and/or the ionic liquid N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide. Cyclic Voltammetry and Electrochemical Impedance Spectroscopy revealed that, increasing the relative amount of ionic liquid in the electrolytes, the impedance decreased and the ionic

The activity of transparent and highly porous nanocrystalline TiO2 electrodes for phenol degradation by heterogeneous photocatalysis was investigated. Electrochemical characterization, performed for electrodes with areas=1.0cm2, revealed that the capacitance values increased under irradiation. Electrodes with areas=9.0cm2 were used for remediation of 10mL of an aqueous solution containing 50mgL−1 of phenol. Irradiated by a solar simulator, removal of 48% of total

ABSTRACT ZnO nanowires (NWs) grown by the hydrothermal method on fluorine-doped tin oxide glass substrate were characterized by scanning electron microscopy, optical absorption, photoelectrochemical photocurrent density, and ultrafast transient absorption pump probe spectroscopy. The as-grown NWs were annealed in air, pure hydrogen atmosphere, or annealed first with air annealing followed by hydrogen treatment. By TA spectroscopy, the samples exhibited a triple exponential transient bleach recovery with lifetimes on the fast (10–15 ps), medium (100–200 ps), and slow (>1 ns) time scale, attributed to shallow donor mixed with electron hole plasma recombination, donor bound recombination, and donor–acceptor pair recombination (DAP), respectively. The as-grown samples were dominated by donor and DAP recombination. Air annealing improved the crystal structure but had little effect on hole trapping. Significantly, the hydrogen-treated NWs showed a reduction in hole trapping and DAP recombination. Hole trapping was attributed to zinc vacancies (VZn) and hydrogen was proposed to passivate these defects. The photocurrent density of the air annealed and cotreated NWs were measured, the latter of which showed improved performance which was attributed to, in part, decreased hole trap states and improved electrical conductivity. In situ ultrafast TA spectroscopy was used to study the photoanodes under working conditions as a function of applied bias. For both samples, the medium time constant became faster with increasing applied bias. A model was proposed to extract the electron–hole separation time constant.