Jinghuai Fang

Sensitization of nanocrystalline TiO2 electrode with quantum sized CdSe and ZnTCPc molecules

Abstract The transparent titanium dioxide (TiO 2 ) electrode with large surface roughness factor was prepared on a conducting glass support. Modification of the TiO 2 electrode with Q-CdSe particles could extend the optical absorption spectrum and photocurrent action spectrum into visible range. Q-CdSe/TiO 2 electrode not only could the photoresponse be further extended into red region by sensitization with phthalocyanine dye molecules, but also facilitates the photon-to-photocurrent conversion efficiency of the electrode. This is the first report about co-sensitization of TiO 2 electrode by combination of Q-sized particles and phthalocyanine dye molecules.

Co-sensitization of microporous TiO2 electrodes with dye molecules and quantum-sized semiconductor particles

Abstract The microporous titanium dioxide (TiO2) film has been prepared on a conducting glass substrate. A seven-fold enhancement in energy conversion efficiency of the dye-sensitized solar cell was achieved by pre-depositing a closely packed TiO2 thin film on the surface of the conducting glass. Moreover, FeS2 particles were coated on TiO2 electrode by chemical reaction of iron pentacarbonyl with sulfur in xylene. Both atomic force microscope (AFM) and photoelectric studies suggest that the FeS2 quantum-sized particles play a dominate role in the photoelectric conversion of FeS2/TiO2 electrode, while the FeS2 large particles have less or even no contribution to the photo-current. Furthermore, the TiO2 electrode has been co-modified with phthalocyanine dye molecules and quantum-sized semiconductor particles. Co-sensitization of the TiO2 electrode with CdSe particles and ZnTCPc dye molecules not only extends the photoresponse of CdSe/TiO2 electrode further into red region, but also improve the quantum efficiency of photoelectric conversion. We believe that such a co-sensitization technique should be of general importance in designing novel solar energy conversion devices.

The photovoltaic study of co-sensitized microporous TiO2 electrode with porphyrin and phthalocyanine molecules

Abstract A TiO2 microporous electrode is modified simultaneously with porphyrin dye molecules and phthalocyanine dye molecules by chemical adsorption. Since porphyrin and phthalocyanine dye have a different spectral region for absorption of visible light, the TiO2 electrode modified with these two dyes could more effectively absorb visible light. Experimental results show that the sensitization of TiO2 electrode with porphyrin and phthalocyanine dyes effectively extends the optical absorption spectrum and photocurrent spectrum into a wider visible range and exhibits a significant improvement of photoresponse compared to the of a single dye modified electrode.

Investigation of alignment properties of Langmuir-Blodgett monolayers by scanning tunneling microscopy

Abstract The surface structures of lecithin Langmuir-Blodgett monolayers are directly observed by scanning tunneling microscopy (STM). At high surface pressures the monolayers show close structures, while at low surface pressures the monolayers show loose structures. The different surface structures have different efficacies for aligning the nematic liquid crystal MBBA. A possible alignment mechanism is proposed based on the STM results.

Investigation of Alignment Mechanism of Polyimide Langmuir-Blodgett Films on Liquid Crystal

Abstract The homogeneous alignment of liquid crystals, 4′-n-octyl-4-cyanobipheny(8CB), was achieved by polyimide Langmuir-Blodgett(LB) films. The surfaces of the polyimide LB films were examined by scanning electron microscopy and scanning tunneling microscopy. Experimental results indicate that the alignment of the polyimide L.B films with grooveless surfaces occur due to the orientation of polyimide chains.

Photovoltaic study of nanocrystalline TiO2 film modified with dye molecules

The nanocrystalline TiO2 film is modified simultaneously with porphyrin dye molecules and phthalocyanine dye molecules by chemical adsorption. Since porphyrin and phthalocyanine dye have different absorption character in the visible range, the TiO2 electrode sensitized by a combination of porphyrin and phthalocyanine dye molecules not only obtains a better spectral match to the solar spectrum, but also the photoresponse of the electrode is extended to cover most of the visible range. This kind of electrode exhibits a significant improvement of energy conversion efficiency.

Ultrathin conductive films prepared by pyrolysis of photosensitive polyimide langmuir-Blodgett films

The ultrathin conductive films were prepared by pyrolysis of photosensitive polyimide LB films at 1000°C in hydrogen atmosphere. The conductivity of these pyrolyzed LB films increased with the film thickness and reached the stable value of 180 s cm-1. The pyrolyzed LB films on the silicon dioxide substrate were studied by scanning tunneling microscope.

Investigation of alignment mechanism of liquid crystal on polyimide Langmuir-Blodgett films by scanning tunnelling microscopy

Abstract The homogeneous alignment of a liquid crystal material, 4′-n-octyl-4-cyanobiphenyl (8CB), was achieved by polyimide Langmuir-Blodgett (LB) films. Scanning electron microscopy and scanning tunnelling microscopy measurements show that the alignment of the polyimide LB films with a grooveless surface occurs due to the orientation of the polyimide chains. We directly observe 8CB monolayers on oriented polyimide LB films. We find that the monolayers form a two dimensional crystalline structure and the 8CB molecules are always aligned along the chain direction of the polyimide. The results show that the alignment of 8CB molecules arises by an epitaxial growth on the oriented polyimide LB films.

Fabrication, characterization and photovoltaic study of a GaTSPc–CdS/TiO2 particulate film

Quantum-sized cadmium sulfide (CdS) particles have been deposited onto the surface of a microporous titanium dioxide (TiO 2 ) electrode by the chemical growth method, followed by modification with gallium tetrasulfophthalocyanine (GaTSPc) molecules to prepare a co-modified TiO 2 electrode. Low bandgap semiconductor CdS particles and GaTSPc have different spectral ranges in the visible range. The co-modified TiO 2 electrode effectively absorbed visible light. Experimental results showed that the sensitization of the TiO 2 electrode with CdS and GaTSPc extended the optical absorption spectrum and photocurrent action spectrum into a wider visible range; moreover, the CdS/TiO 2 coupled structure facilitated the photon-to-photocurrent conversion efficiency.

Homogeneous Alignment of a Nematic Liquid Crystal by a Pyrolyzed Polyimide Langmuir-Blodgett Film

Abstract The pyrolyzed polyimide Langmuir-Blodgett film can provide an aligning layer and an electrode for liquid crystal cells. The LB film surface is characterized by Scanning electron microscopy, scanning tunneling microscopy and optical absorption spectra. We find that the aligning and conducting mechanism is due to the presence of carbon enriched islands in the LB film. The electrooptical effects in twisted nematic liquid crystal cells using the films as electrodes and aligning layers are observed.