Electron Transfer Layer Research Articles

Improved Conversion Efficiency of Organic Solar Cells with CuPc/C60 Heterostructure by Electron Transfer Layers

In this paper, we investigated the role of electron transport layer (ETL) on the organic solar cells. By using 2-(4-Biphenylyl)-5-(4-tert-butylphenyl)-1, 3, 4-oxadiazole (PBD), bathocuproine (BCP) and tris (8-hydroxy-quinolinato) aluminium (Alq3) were used as ETLs. It was observed that the PCE of device with BCP layer was greatly improved compared with devices with other ETLs. The performance improvement was analyzed in terms of energy diagram level, UV/vis absorption spectra.

Improved Conversion Efficiency of Organic Solar Cells with CuPc/C60 Heterostructure by Electron Transfer Layers

not Available.

Reduced efficiency roll-off in phosphorescent organic light emitting diodes at ultrahigh current densities by suppression of triplet-polaron quenching

High-performance phosphorescent organic light emitting devices with reduced efficiency roll-off at ultrahigh current densities were realized. The devices were Ir(ppy)3-based phosphorescent organic light emitting diodes that employed 1,3-bis[2-(2,2′-bipyridine-6-yl)-1,3,4-oxadiazo-5-yl]benzene as a high mobility electron transfer layer. The device’s brightness was enhanced while the efficiency roll-off was reduced. The device exhibits high current efficiency (21cd∕A) at high brightness (80000cd∕m2), with a maximum luminescence of 136000cd∕m2 at over 1A∕m2 (with an efficiency of 13cd∕A). This reduction in efficiency roll-off is attributed to the suppression of the triplet-polaron quenching rate through balancing the charge carrier ratio in the device.

Efficient Organic Light-emitting Diode Using Lithium Tetra-(8-hydroxy-quinolinato) Boron as the Electron Injection Layer

High performance organic light-emitting diodes (OLEDs) with lithium tetra-(8-hydroxy-quinolinato) boron (LiBq 4), instead of LiF, as the electron injection layer, and aluminum as the cathode were fabricated. In the fabrication of the devices, N,N′-bis-(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) was used as the hole transfer layer, and tri-(8-hydroxyquino-line) aluminum (Alq3) as the emitting and electron transfer layer. By using LiBq4 as the electron injection layer, the devices performance with regard to luminance, current efficiency, and turn-on voltage was superior to that of the device using LiF as the electron injection layer. The experimental results could be explained by the improved electron injection and charge balance.

Organic/inorganic heterostructures for enhanced electroluminescence

In this work, organic/inorganic heterostructure electroluminescence devices are fabricated, in which the inorganic layers (ZnO, ZnS) act as the electron transfer layer and the hole blocking layer. Compared to single-organic-layer (MEH-PPV) devices, the heterostructure devices have a significantly enhanced luminous efficiency. The influences of the electric field and the barrier potential on the improvements in performance are analyzed in detail. The results are: (i) the introduction of the inorganic layer makes the injection of electrons easier; (ii) the hole current density is enhanced by the increase of the electric field in the organic layer due to a high dielectric constant of the inorganic layer and accumulation of electrons at the inorganic/organic interface; (iii) the electron–hole current density balance is improved.

Reverse-polarity direct current plasma-driven electro-reduction of refractory metals in molten oxide melts

This work is concerned with the extraction of refractory metals using an electro-reduction process in which a molten oxide melt, instead of halide, is used as the electrolyte. The process may provide an alternative method for producing refractory metals from their ores through the use of a reverse-polarity direct current (DC) plasma arc heating process. In such a process, the plasma torch itself acts as an anode, and the resulting liquid or solid product metals work as a cathode, whereas the molten oxide melt plays the role of an electron transfer layer. The focus of this study is the electro-reduction of scheelite, vanadium pentoxide and chromite. For vanadium pentoxide, the proposed melt is mainly composed of CaO-V2O5/Li2O-B2O3-V2O5 orFeO-CaO-SiO2-V2O5-Li2O with the addition of other alkali and alkaline metal oxides. In the case of scheelite ore, the SiO2-CaO-Li2O-WO3 system is used as melt and metal aluminum or nickel could be used as a collecting media. As for the reduction of chromite ore, SiO2-CaO-Cr2O3-Li2O system with a small amount of CaF2 is used as the melt. As a demonstration, chromium was successfully produced on a laboratory scale through the plasma-driven electro-reduction process. One of the studied slags had a composition of 13.8% CaO, 4.9% CaF2, 36.4% Cr2O3, 6.9% Li2O and 38.0% SiO2. Two observations are significant in this laboratory-scale study. The first was that the amount of Cr2O3 and FeO, which were predominantly electronic conductors in the oxide melt, greatly affected the conducting mechanism of the melt. With high concentrations of Cr2O3 and FeO in the melt, the current efficiency was fairly low. In this case, chromium was found to be slightly reduced due to electronic conducting mechanism. For example, with an initial slag of 60% Cr2O3, no chromium was found reduced. With low concentrations of Cr2O3 and FeO in the studied melt, typically no more than 30% Cr2O3, it was observed that chromium was readily reduced due to the dominant ionic conducting mechanism. The second observation was that the addition of SiO2 to the melt helped to make the oxide melt more ionic, which was apparently desirable to the molten oxide electrolysis. However, a high content of silica had a negative effect on the fluidity of the melt. This was resolved by adding trace amounts of CaF2 to the melt. Therefore, by judicious selection of oxide melt, refractory metal oxides might be dissolved into it, and yet the melt itself retains the required ionicity. A reverse-polarity DC-plasma-driven molten oxide electrolysis may prove to be a viable alternative route for the extractive metallurgy of refractory metals.

Quinolinate zinc complexes as electron transporting layers in organic light-emitting diodes

We describe the synthesis and properties of a bis(8-quinolinolato- N 1, O 8)-zinc(II) complex (Znq 2) which can be used as an efficient electron transfer layer in organic light-emitting diodes. In this material, the electrons are much more mobile at room temperature than in the well-known tris(8-quinolinolato- N 1, O 8)-aluminium(III) complex (Alq 3). Preliminary results concerning a series of related compounds are presented.

Novel main-chain poly-carbazoles as hole and electron transport materials in polymer light-emitting diodes

We report the use of substituted main-chain poly-carbazoles as hole and electron transporting polymers for electroluminescence (EL) applications. The polymers are soluble in common organic solvents and high quality thin films are obtained by spin coating method. A single layer of hole or electron transfer devices with indium tin oxide anode and aluminum cathode shows current densities up to 40–50 mA/cm2, respectively, but no visible emission from either layer. Double-layer structures combining the hole and electron transfer polymers show strong emission originated from the electron transfer layer. The peak of double-layer EL spectrum is about 30 nm redshifted to the peak of corresponding photoluminescence spectrum, which may be due to the formation of an exciplex between the two layers.

EDITORIAL

The German Bunsen Society for Physical Chemistry celebrates its centenary in Berlin in May. Angewandte Chemie extends its congratulations and therefore dedicates this issue, which includes a review by John M. Thomas, to the topic of catalysis. Physical chemistry continues to offer a wide variety of attractive research topics—high‐resolution spectroscopy, electron transfer, clusters, catalysis, and thin layers, to name a few. By publishing many reviews Angewandte Chemie has informed chemists of new developments in physical chemistry and will continue to do so. Communications and highlights provide a forum for the rapid presentation of important new results. The manuscripts that we receive testify that Angewandte Chemie has recently become even more attractive to physical chemists, and we are happy that we can accommodate these fine papers thanks to our expanded volume.