Electrosynthesis of organic–inorganic compounds (p–n heterojunction)

An electrochemical deposition procedure by cyclic voltammetry, in an electrolyte solution was adopted for the preparation of thin films of polypyrrole–gallium arsenide composite materials. The properties of the composite layers were studied by cyclic voltammetry, electrochemical impedance spectroscopy and photoelectrochemical measurements. The p- and n-type semiconductor behaviour of the polypyrrole (PPy) and gallium arsenide (GaAs) were studied by photocurrent measurements. It was found that the composite material (PPy–GaAs) had a (p–n) heterojunction behaviour

Optical and photo-electrochemical characterization of organic-inorganic photosensitive materials

This work reports on the optical and photoelectrochemical properties of polybithiophene (PBiTh) films electrochemically synthesized onto indium-tin oxide (ITO) substrates and modified with incorporation of indium phosphide (InP) when present in solution during polymerization. The properties of the composite layers were studied by electrochemical method (cyclic voltammetry), scanning electron microscopy (SEM), UV-vis spectroscopy and photocurrent measurements. From UV-vis spectroscopy studies, the absorbance of the composite is larger than the polybithiophene absorbance in the UV region. The cathodic photocurrent reflected the p-type semiconductor behaviour of the electrosynthesized polybiththiophenes. Addition of InP semiconductors the improves the photocurrent at cathodic potential ( 4 ¿A/cm2 at 100 mW/cm2) indicating the acceptor molecule acts as an exciton dissociation center, improving the number of charge carriers transported through the polymer to reach the solid-liquid electrolyte interface. It was found that the photosensitive composite material (PBiTh-InP) has good photoelectrochemical and optical properties

Electro-synthesis, characterization and photoconducting performance of ITO/polybithiophene–MnO2 composite

International audiencetManganese dioxide is synthesized by reduction reaction of potassium permanganate with hydrogenperoxide. The as-synthesized -MnO2is characterized by powder X-ray diffraction and infrared spec-troscopy. The MnO2particles are used to prepare composite films containing polybithophene (PBTh) onindium tin oxide (ITO) glass substrates. The composite films ITO/PBTh–MnO2are obtained by electro-polymerization of bithiophene in the presence the -MnO2particles dispersed in the electrolytic solution.The XRD and SEM analyses show that the -MnO2particles of size in the range 100–300 nm are incorpo-rated in the polymer. The films are characterized by cyclic voltammetry impedance spectroscopy, UV–visspectroscopy and scanning electron microscopy. As a result, the electrochemical gap and the opticalgap are shifted by the incorporation of MnO2from 2.15 eV for ITO/PBTh to 1.88 eV for ITO/PBTh–MnO2,while the electrical conductivity decreases from 195.35 S/cm for ITO/PBTh down to 0.047 S/cm forITO/PBTh–MnO2at the highest MnO2investigated. The photo-electrochemical measurements also indi-cate that the ITO/PBTh–MnO2films show a photocurrent that is three times higher than that of ITO/PBThsubstrate to reach 20.6 A cm−2, so that such a composite can be used as a new active material insolar cells

Effects of pulsed electrodeposition parameters on the properties of zinc oxide thin films to improve the photoelectrochemical and photoelectrodegradation efficiency

International audienceZinc oxide (ZnO) thin films were synthesized on ITO glass substrates by electrochemical deposition from a nitrate solution. The deposition potential, bath temperature and annealing temperature were fixed at -1.1 V versus SCE, 80 and 400 degrees C, respectively. Firstly, we prepared the ZnO thin films by two different electrochemical methods: direct (DE) and pulsed electrodeposition (PE). The results indicate that pulse electrodeposition improves the properties of ZnO thin films compared to direct electrodeposition technique. Secondly, we chose the PE method for the elaboration of ZnO thin films and we varied the time-On (t(on)) from 7 to 1 s. Deposited ZnO thin films were characterized using XRD, SEM, optical and photocurrent measurement. X-ray diffraction results indicate that the synthesized ZnO has a pure hexagonal wurtzite structure with a marked preferential orientation along the (002) plane perpendicular to the substrate. SEM analysis reveals that the electrodeposited nanosheets at time-On of 7 s are only hexagonal. A remarkable change in ZnO morphology from nanosheets to nanosheets/nanorods and decrease in gap energy is observed with the decrease in electrodeposition time-On. After optimization in electrodeposition time (t(on)), a significant improvement in photocurrent and Methylene Blue (MB) photoelectrocatalytical degradation were observed