Papers by Keyword: Photoelectric Property

Abstract: The principle and experimental setup of photoelectric property measurement withTime of Flight (TOF) method are described. Si sample is used to affirm thevalidity of the experiment setup. The photoelectric property of MEH-PPVmaterials is measured and the mobility is accounted base on TOF method. Moreover,the attention items of using TOF method are proposed. The results consist well with the theoretical value.

Abstract: In this paper, TiO₂ thin film with MSM (metal-semiconductor-metal) structure was used to fabricate ultraviolet (UV) detector. The film was fabricated via sol-gel method on silicon wafer with 300nm oxide layer and annealed at four different temperatures (400oC, 500oC, 600oC and 800oC). The quality of the thin films was characterized by means of X-ray diffraction and scanning electron microscope. Then a pair of symmetric Ag electrodes were deposited by thermal evaporation through a shade mask of interdigital structure. The photo-electric properties of the device including I-V characteristic, transfer characteristic and time response et.al. were studied with or without explored to 254nm UV light. The electrical measurements of the device show a big increase of current when explored the device to 254nm UV light, and the rise time of the device is very quick, but the fall time is relatively long. The detector with simple fabrication process, low cost, and superior performance would provide a potential application in UV detectors.

Abstract: Anatase TiO2- thin films on glass substrates were prepared by sol-gel dip-coating method. We designed a multi-round annealing process which was under the air pressure of 5 Pa and then 5×10-2 Pa for one hour each at 550 °C, and such process was repeated for three times. The special designed annealing process can obviously improve the conductivity of the udoped TiO2- thin films. The minimum resistivity of the undoped TiO2- thin films reached 0.8 Ω cm after being treated by the multi-round annealing process. It was demonstrated that such annealing process was an effective way to increase the defects in TiO2- thin films such as oxygen vacancies. The average transmittances of the films were approximately 60~80% in the visible range with the forbidden gaps of 3.25~3.35 eV. After the multi-round annealing process, the optical forbidden gaps of the films became narrowed slightly, which might be also related to the defects introduced during the multi-annealing process.

Abstract: Indium tin oxide (ITO) films were deposited on glass substrates by using the homemade spray pyrolysis system. Orthogonal test was designed to examine the optimal conditions for preparation of the ITO films. The results showed that the ITO thin films can be prepared by the homemade spray pyrolysis device successfully. The device is simple in structure and easy to use. The substrate temperature is the main factor on the photoelectric properties of the ITO films. The optimal conditions for preparing the ITO thin films were as following: the substrate temperature is 300oC, the carrier gas flow of the air was 1.5 L•min-1, the annealing temperature was 500oC, the proportion of the indium and tin was 10:1, the distance between substrate and nozzle was 8 cm, and the deposition time was 3.5 min. The average optical transmittance in the visible range and sheet resistance of the ITO film were 93% and 2786Ω/□, respectively.

Abstract: Experiments with ZnO Metal-Oxide-Semiconductor （MOS） under different circumstances were made to get four different I-V curves. There were four conditions: dark, and tests with the green, blue, ultraviolet LED light. According to references, three parameters B，V_B0 and N_barr could be acquired by fitting lines of the I-V curves using MATLAB and LabVIEW. From their definitions, B, V_B0 and N_barr indicate photoelectric properties of ZnO cooperatively under concrete conditions. V_B0, grain boundary potential, is parameter of extrinsic properties of ZnO determined by both ZnO and testing conditions. So V_B0 is critical to control the photoelectric properties of ZnO. A smaller V_B0, the stronger the photoelectric response of ZnO and the lager the efficiency of photoelectric conversion. Besides, this theory can be expanded to test the photoelectric properties of the other semiconductor materials. And I-V curves can direct the application of these materials efficiently.

Abstract: The critical material of photo-anode, the TiO₂ nano-particles, as the most important component in dye sensitized solar cells (DSSCs) was studied in this paper. The TiO₂ nanoparticles were prepared by the method of micro-emulsion. In the process of preparation, the factors including the kinds of surfactant, and the molar ratio of water to titanium (R value) were investigated. Finally, the optimal condition for the preparation of the TiO₂ nano-particles was determined. When Tx-100 was used as the surfactant and R was 35, the TiO₂ nano-particles were prepared and used as photo-anode in the DSSCs, which were sensitized by N719, test under AM1.5G sunlight. The highest photoelectric conversion efficiency was achieved: Short-circuit photocurrent (Isc) =13.91mA/cm², open-circuit photo voltage (Voc) =0.83V, fill factor (FF) =55.06%, photoelectric conversion efficiency (η) =6.36%.

Abstract: ZnSe is a kind of important semiconductor photo-electricity materials, which has received common attentions. The preparation and photoelectric property of high quality ZnSe single crystal have become the focus on current research fields. In this paper, the preparation methods were discussed emphatically and optical and electrical properties were analyzed on these bases. Furthermore, the application prospective was discussed. Therefore, this paper provided research basis for preparation and application of ZnSe.

Abstract: SnS and Ag films were deposited on glass substrates by vacuum thermal evaporation successively, and then the thin films were annealed at 260°C in N2 for different times (60min, 120min, 180min) in order to investigate the influence of annealing time on the silver-doped SnS (SnS:Ag) films. The obtained films annealed at different times are polycrystalline SnS with orthogonal structure, and the crystallites in the films are exclusively oriented along the {111} direction. With the increase of annealing time, the uniformity and crystallization of the films are improved, the carrier concentration and mobility of the films first rise and then drop, whereas their resistivity and direct bandgap energy Eg show the contrary trend.

Abstract: Nanocrystalline titania porous films were prepared on ITO and glass substrates by polyethylene glycol（PEG）-assisted sol-gel method using Ti(C4H9COO)4 as precursor, ethanol as solvent and NH(C2H2OH)2 as chelating agent and PEG 2000as a template. When the amount of polyethylene glycol is within the range of 0～2. 0g/L ,. The characteristics and microstructure of films as well as the chemical and physical changes taken place during so-gel and heat treatments were analyzed by XRD, SEM and Emission spectra. The Cyclic voltammetry which measurements the films by illumination with a high pressure mercury lamp are employed to analyze photoelectrochemical property the porous titania thin films. The effects of precursor concentration and PEG 2000 contention the characteristic of films were discussed. The Cyclic voltammetry experiment under UV light irradiation indicated that the pores in the TiO2 thin films enhanced its photoelectrochemical activity; the size of the pores thin films obviously affected the photo-current exchanged rate of titania films.

Abstract: This work focuses on studying a novel polymer/nanocrystal multilayer for the fabrication of donor and accepter typed photovoltaic device. Highly luminescent anionic CdTe nanocrystals were prepared by aqueous synthesis method using 3-mercaptopropionic acid as stabilizer. The resultant CdTe served as electron acceptor and poly(p-phenylene vinylene) (PPV) was used as electron donor. Through the electrostatic interactions between cationic PPV precursor poly(p-xylene tetrahydrothiophenium chloride) and anionic poly(sodium4-styrenesulfonate) (PSS), PPV/PSS complex was fabricated on the surface of pretreated quartz substrate by layer-by-layer electrostatic self-assembly method. UV-Vis spectrum shows that PSS in the PPV/PSS complex make PPV precursors thermally convert into PPV at a lower temperature and less time. PPV/ PSS/PPV/CdTe multilayer were fabricated on the surface of quartz substrate by electrostatic self-assembly method. The surface of the polymer/CdTe complex is flat, which was characterized by atomic force microscopy (AFM). UV-Vis spectrum of the polymer/CdTe complex shows that the absorbance increases with the increase of the number of deposition cycles. In the same way, PPV/PSS/PPV/CdTe multilayer were fabricated on the surface of ITO substrate disposed by the poly(3,4- ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS). The resultant polymer/ CdTe complex is measured under AM1.5G simulated solar illumination with 100mW•cm-2 in air. The open circuit current density (VOC) and short circuit current density (JSC) of the polymer/CdTe complex are 0.60 V and 0.305 mA•cm-2 which are better than PPV or CdTe nanocrystal individual. This could be ascribed to interfacial hole-electron converter between the conjugated polymer layer and CdTe nanocrystal layer. Besides, the photovoltaic properties of PPV/CdTe complex can be improved by controlling the layers of PPV/ CdTe nanocrystals complex on the ITO substrate.