Effects of thermal annealing on polymer photovoltaic cells with buffer layers and in situ formation of interfacial layer for enhancing power conversion efficiency

We have investigated the effects of thermal annealing before and after cathode deposition on poly(3-hexylthiophene)(P3HT)/[6,6]-phenyl C61-butyric acid methyl ester (PCBM) blend photovoltaic cells with different cathode buffer layers. The introduction of cathode buffer layer such as lithium fluoride (LiF) and calcium oxide (CaO) in pre-annealing cells can increase the open-circuit voltage (V-oc) and the power conversion efficiency (PCE). Post thermal annealing after cathode deposition further enhanced the PCE of the cells with LiF/Al cathode.

Preparation and photovoltaic property of a new polyfluorene derivative/ZnO nanoparticles hybrid composites

A new kind of polyfluorene copolymers, poly(2,7-(9,9-dioctyl-fluorene)-alt-5,5 -(4',7'-di-2-thienyl-2',1',3',-benzothiadiazole) (PFDTBT), was prepared. The introduction of ZnO nanoparticles with perfect wurtzite crystal character into PFDTBT makes the resulted single-layer photovoltaic device to perform a significant photovoltaic response. Among the tested devices, the best performance is observed for that containing 60 wt% of ZnO nanoparticles, which has a photocurrent density of 1.17 mu A/cm(2), an open circuit voltage of 0.81 V. a fill factor of 0.09 and a power conversion efficiency of 0.009%. The results show that the polyfluorene derivatives/ZnO nanoparticles hybrid composites are excellent fluorescence and photovoltaic materials. (C) 2009 Elsevier B.V. All rights reserved.

Preparation and photovoltaic property of a new polyfluorene derivative/ZnO nanoparticles hybrid composites

A new kind of polyfluorene copolymers, poly(2,7-(9,9-dioctyl-fluorene)-alt-5,5 -(4',7'-di-2-thienyl-2',1',3',-benzothiadiazole) (PFDTBT), was prepared. The introduction of ZnO nanoparticles with perfect wurtzite crystal character into PFDTBT makes the resulted single-layer photovoltaic device to perform a significant photovoltaic response. Among the tested devices, the best performance is observed for that containing 60 wt% of ZnO nanoparticles, which has a photocurrent density of 1.17 mu A/cm(2), an open circuit voltage of 0.81 V. a fill factor of 0.09 and a power conversion efficiency of 0.009%. The results show that the polyfluorene derivatives/ZnO nanoparticles hybrid composites are excellent fluorescence and photovoltaic materials.

Highly ordered mesoporous carbons-based glucose/O-2 biofuel cell

This study demonstrates a novel compartment-less glucose/O-2 biofuel cell (BFC) based on highly ordered mesoporous carbons (OMCs) with three-dimensionally (3D) interconnected and ordered pore structures. OMCs are used as supports for both stably confining the electrocatalyst (i.e., meldola's blue, MDB) for NADH oxidation and the anodic biocatalyst (i.e., NAD(+)-dependent glucose dehydrogenase, GDH) for glucose oxidation, and for facilitating direct electrochemistry of the cathodic biocatalyst (i.e., laccase, LAC) for O-2 electroreduction. In 0.10 M pH 6.0 PBS containing 20 mM NAD(+) and 60 mM glucose under the air-saturated atmosphere, the open circuit voltage (0.82 V) and the maximum power output (38.7 mu W cm(-2) (at 0.54V)) of the assembled compartment-less OMCs-based BFC are both higher than those of carbon nanotubes (CNTs)-based BFC (0.75 V and 2.1 mu W cm(-2) (at 0.46 V)).

Efficient tandem polymer photovoltaic cells with two subcells in parallel connection

Tandem polymer photovoltaic cells with the subcells having different absorption characteristics in series connection are widely investigated to enhance absorption coverage over the solar spectrum. Herein. we demonstrate efficient tandem polymer photovoltaic cells with the two stacked subcells comprising different band-gap conjugated polymer and fullerene derivative bulk heterojunction in parallel connection. A semitransparent metal layer combined with inorganic semiconductor compounds is utilized as the intermediate electrode of the two stacked subcells to create the required built-in potential for collecting photo-generated charges. The short-circuit current of the stacked cell is the sum of the subcells and the open-circuit voltage is similar to the subcells.

A plasma sputtering decoration route to producing thickness-tunable ZnO/TiO2 core/shell nanorod arrays

We report a radio frequency magnetron sputtering method for producing TiO2 shell coatings directly on the surface of ZnO nanorod arrays. ZnO nanorod arrays were firstly fabricated on transparent conducting oxide substrates by a hydrothermal route, and subsequently decorated with TiO2 by a plasma sputtering deposition process. The core/shell nanorods have single-crystal ZnO cores and anatase TiO2 shells. The shells are homogeneously coated onto the whole ZnO nanorods without thickness change. This approach enables us to tailor the thickness of the TiO2 shell for desired photovoltaic applications on a one-nanometer scale. The function of the TiO2 shell as a blocking layer for increasing charge separation and suppression of the surface recombination was tested in dye-sensitized solar cells. The enhanced photocurrent and open-circuit voltage gave rise to increased photovoltaic efficiency and decreased dark current, indicating successful functioning of the TiO2 shell.

Progress in polymer solar cell

This review outlines current progresses in polymer solar cell. Compared to traditional silicon-based photovoltaic (PV) technology, the completely different principle of optoelectric response in the polymer cell results in a novel configuration of the device and more complicated photovoltaic generation process. The conception of bulk-heterojunction (BHJ) is introduced and its advantage in terms of morphology is addressed. The main aspects including the morphology of photoactive layer, which limit the efficiency and stability of polymer solar cell, are discussed in detail. The solutions to boosting up both the efficiency and stability (lifetime) of the polymer solar cell are highlighted at the end of this review.

Surface-modified Nafion (R) membrane by casting proton-conducting polyelectrolyte complexes for direct methanol fuel cells

Surface-modified Nafion (R) membrane was prepared by casting proton-conducting polyelectrolyte complexes on the surface of Nafion (R). The casting layer is homogeneous and its thickness is about 900 nm. The proton conductivity of modified Nafion (R) is slightly lower than that of plain Nafion (R); however, its methanol permeability is 41% lower than that of plain Nafion (R). The single cells with modified Nafion (R) exhibit higher open circuit voltage (OCV = 0.73 V) and maximal power density (P-max = 58 mW cm(-2)) than the single cells with plain Nafion (R) (OCV = 0.67 V, P x = 49 mW cm-2). It is a simple, efficient, cost-effective approach to modifying Nafion (R) by casting proton-conducting materials on the surface of Nafion (R).

Low temperature preparation and fuel cell properties of rare earth doped barium cerate solid electrolytes

The solid electrolytes, BaCe(0.8)Ln(0.2)O(2.9) (Ln: Gd, Sm, Eu), were prepared by the sol-gel method. XRD indicated that a pure orthorhombic phase was formed at 900 degrees C. The synthesis temperature by the sol-gel method was about 600 degrees C: lower than the high temperature solid phase reaction method. The electrical conductivity and impedance spectra were measured and the conduction mechanism was studied. The grain-boundary resistance of the solid electrolyte could be reduced or eliminated by the sol-gel method. The conductivity of BaCe0.8Gd0.2O2.9 is 7.87 x 10(-2) S.cm(-1) at 800 degrees C. The open-circuit voltage of hydrogen-oxygen fuel cell using BaCe0.8Gd0.2O2.9 as electrolyte was near to 1 V and its maximum power density was 30 mW.cm(-2).

DEVELOPMENT OF CYLINDRICAL SECONDARY LITHIUM POLYANILINE BATTERIES

The cylindrical 'D'-size batteries were fabricated by polyaniline paste cathode and lithium foil anode sandwiched with microporous polypropylene separator. The electrolyte used was LiClO4 dissolved in a mixed solvent of propylene carbonate and dimethoxyethane. The results of charge/discharge curves, charge/discharge cycles, the short-circuit current, the open-circuit voltage storage and the change of discharge capacity with temperature, discharge current are reported.

A WOUND-TYPE LITHIUM POLYANILINE SECONDARY CELL

A wound-type cell with a polyaniline (PAn) positive electrode, a LiClO4-propylene carbonate (PC) electrolyte, and a lithium foil negative electrode has been constructed. The two electrodes are separated by a polypropylene separator. The PAn is deposited on carbon felt from a HClO4 solution containing aniline by galvanostatic or potentiostatic electrolysis. Using cyclic voltammetry charge/discharge cycles and charge/retention tests, the following results have been obtained: (i) reversibility of the charge/discharge reaction of the PAn electrode is very good; (ii) more than 50 charge/discharge cycles at 80% charge/discharge efficiency and 260 W h kg-1 discharge energy density can be achieved at 50 mA between 2 and 4 V; (iii) the open-circuit voltage and the capacity retention of the battery after storage at open-circuit for 60 days are 3.4 V and 33%, respectively.

Ethanol crossover phenomena and its influence on the performance of DEFC

In the present work, Nafion (R) membrane porosity changes were determined in aqueous ethanol solutions with different concentrations by weighing vacuum-dried and ethanol aqueous solution equilibrated membranes at room temperature. The ethanol crossover rate through Nafion (R)-115 membrane at different temperatures and different concentrations had been investigated in a fuel cell test apparatus by using membrane gets higher as ethanol solution gas chromatography analysis. The experimental results show that the swelling degree of Nafion (R) concentration increases. The ethanol crossover rate increases with ethanol concentration and temperature increment. The single direct ethanol fuel cell (DEFC) tests were carried out to investigate the effect of ethanol concentration on ethanol crossover and consequently, on the open circuit voltage and the cell performance of DEFC. It can be found that ethanol crossover presented a negative effect on the OCV and the cell performance of DEFC. It can also be found that an improved DEFC performance was obtained as temperature increased although the ethanol crossover rate increased with temperature increment. (c) 2005 Elsevier B.V. All rights reserved.

A novel PTFE-reinforced multilayer self-humidifying composite membrane for PEM fuel cells

A novel polytetrafluoroethylene (PTFE)-reinforced multilayer self-humidifying composite membrane is developed. The membrane is composed of Nafion-impregnated porous PTFE composite as the central layer and nanosized SiO2 supported Pt catalyst imbedded into Nafion as the two side layers. The proton exchange membrane (PEM) fuel cells employing the self-humidifying membrane (20 mu m thick) under dry H-2/O-2 gave a peak power density of 0.95 W/cm(2) and an open-circuit voltage of 1.032 V. The good membrane performance is attributed to hygroscopic Pt-SiO2 catalyst at the two side layers, which results in enhanced anode side self-humidification function and decreased cathode polarization. (c) 2005 The Electrochemical Society.

Quantum Efficiency And Temperature Coefficients Of Gainp/Gaas Dual-Junction Solar Cell

GaInP/GaAs dual-junction solar cell with a conversion efficiency of 25.2% has been fabricated using metalorganic chemical vapor deposition (MOCVD) technique. Quantum efficiencies of the solar cell were measured within a temperature range from 25 to 160A degrees C. The results indicate that the quantum efficiencies of the subcells increase slightly with the increasing temperature. And red-shift phenomena of absorption limit for all subcells are observed by increasing the cell's work temperature, which are consistent with the viewpoint of energy gap narrowing effect. The short-circuit current density temperature coefficients dJ (sc)/dT of GaInP subcell and GaAs subcell are determined to be 8.9 and 7.4 mu A/cm(2)/A degrees C from the quantum efficiency data, respectively. And the open-circuit cell voltage temperature coefficients dV (oc)/dT calculated based on a theoretical equation are -2.4 mV/A degrees C and -2.1 mV/A degrees C for GaInP subcell and GaAs subcell.

Quantum efficiency and temperature coefficients of GaInP/GaAs dual-junction solar cell

GaInP/GaAs dual-junction solar cell with a conversion efficiency of 25.2% has been fabricated using metalorganic chemical vapor deposition (MOCVD) technique. Quantum efficiencies of the solar cell were measured within a temperature range from 25 to 160A degrees C. The results indicate that the quantum efficiencies of the subcells increase slightly with the increasing temperature. And red-shift phenomena of absorption limit for all subcells are observed by increasing the cell's work temperature, which are consistent with the viewpoint of energy gap narrowing effect. The short-circuit current density temperature coefficients dJ (sc)/dT of GaInP subcell and GaAs subcell are determined to be 8.9 and 7.4 mu A/cm(2)/A degrees C from the quantum efficiency data, respectively. And the open-circuit cell voltage temperature coefficients dV (oc)/dT calculated based on a theoretical equation are -2.4 mV/A degrees C and -2.1 mV/A degrees C for GaInP subcell and GaAs subcell.