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.

No abstract

In this paper, we demonstrated the synthesis and electrochemical properties of macro-/ microporous carbon foams (MMCFs) for application as supercapacitor electrode materials. By using Span 80 and Tween 80 as emulsifiers, resorcinol/formaldehyde solution as aqueous phase, and 1iquid paraffin as oil phase, an O/W emulsion was obtained. Macroporous carbon foams were prepared by the polymerization of the emulsion, followed by drying and carbonization. The macroporous carbon foams then were activated at 1273 K by using KOH as an activated agent to obtain MMCFs. The resultant MMCFs were characterized by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analyzer. The results indicate that the MMCFs have specific surface areas of 529-670 m2/g, total pore volumes of 0.27-0.33 cm3/g and possess dual pore size distributions with macropore sizes of 0.5-5.0 μm and micropore sizes of 1.72-1.86 nm dependent on the specific experiment parameters. The hierarchical pore structure is propitious to decreases the diffusion resistance of electrolyte and accelerate the ion transfer within the pore channel, and thus improve the electrochemical properties of MMCFs. The electrochemical properties of the MMCFs have been investigated by cyclic voltammetry (CV) and galvanostatic charge-discharge with a three-electrode system in electrolyte of 6 mol/L KOH solution. The CV curves of the MMCFs show quite rectangular curve shape without observation of obvious oxidation-reduction evolution peaks, suggesting a typical nonfaradic adsorption/desorption reaction. The MMCFs present linear galvanostatic charge-discharge curve under the current densities of 1.0-4.0 A/g and their specific capacitance values are 89-110 F/g. The MMCFs has good electrochemical performance and they are good candidates as electrode materials for supercapacitors.

We reported the preparation and electrochemical properties of fluorinated mesoporous carbon foams (F-MCFs) for application as electric double-layer capacitors (EDLCs). By using fluorinated resol which was obtained from the polymerization of formaldehyde, phenol, and 3-fluorophenol as the carbon source and fluorin precursor, and triblock copolymer F127 as a template, F-MCFs were prepared through evaporation induced self-assembly strategy. The F-MCFs were characterized by N2 adsorption and desorption, transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). The results indicate that the F-MCFs possess highly ordered mesostructure with a specific surface area of 675 m2/g, a uniform pore size of 2.2 nm and a pore volume of 0.12 cm3/g. The wettability of F-MCFs was investigated by contact angle analysis. The contact angle of F-MCFs for water is 111.5o, much lower than that of mesoporous carbon foams (MCFs) (141o), indicating that the surface wettability of F-MCFs is improved by the introduction of fluorin into the carbon matrix. The enhancement of wettability would increase the surface contact of electrolyte and electrode and accelerate the ion transfer within the pore channel, and thus improve the electrochemical properties of F-MCFs. The electrochemical properties of the F-MCFs have been investigated by cyclic voltammetry (CV) and galvanostatic charge/discharge in electrolyte of 6 mol/L KOH with a three-electrode system. F-MCFs present linear galvanostatic charge-discharge curve at a loading current of 10 mA, and possess good charge-discharge efficiency over 98%. The specific capacitance of the F-MCFs is 220 F/g, significantly higher than that of the MCFs (140 F/g). F-MCFs show important prospect as electrode materials for the application in EDLCs.

Abstract. In this paper, we report the fabrication and photoelectric properties of CdTe/TiO 2 nanocrystal multilayer. Negatively charged CdTe nanocrystal hydrosols were synthesized in the aqueous phase with 3-mercaptopropionic acid as a surface modifier. The characterization of transmission electron microscopy (TEM) and UV-visible absorption spectrum indicates the resultant CdTe nanocrystal hydrosols are monodisperse and have a very narrow size distribution with a mean diameter of about 5 nm. Clear TiO 2 aqueous colloidal nanocrystals with positive surface charges were prepared by using tetrabutyl titanate as precursor. Through the electrostatic interaction between the positive surface charges on TiO 2 nanocrystals and those on CdTe nanocrystal hydrosols, multilayer of CdTe/TiO 2 nanocrystals were fabricated on the pretreated quartz substrate by layer-by-layer electrostatic self-assembly method. UV-Vis absorption spectrum and atomic force microscopy (AFM) were used to characterize the as-prepared CdTe/TiO 2 multilayer. The results show that the surface of the CdTe/TiO 2 multilayer are flat and the adsorption intensity in UV-Vis spectrum increases with the layer numbers of the CdTe/TiO 2 complex, indicating that CdTe/TiO 2 multilayer could be fabricated successfully on the surface of quartz glass and the resultant multilayer have good quality. In the same way, CdTe/TiO 2 multilayer were fabricated on the surface of Indium Tin Oxides (ITO) substrate disposed by the poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS). The CdTe/TiO 2 complex is measured under AM1.5G simulated solar illumination with 100mWcm -2 in air. The results show the maximum open circuit current density (Voc) and short circuit current density (Isc) of CdTe/TiO 2 complex on ITO substrate is 0.45V and 0.050mA, which were better than TiO 2 or CdTe nanocrystal hydrosols individual due to the interfacial hole-electron converter between the adjacent layers of CdTe and TiO 2 nanocrystals.