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Organic Devices (organic + device)

Distribution by Scientific Domains

Polymers and Materials Science	76%

Selected Abstracts

Hybrid Nanoparticle/Organic Devices with Strong Resonant Tunneling Behaviors

ADVANCED FUNCTIONAL MATERIALS, Issue 16 2009
Tianhang Zheng
Abstract A hybrid nanoparticle/organic device consisting of small molecule organic semiconductors and Ag nanoparticles is reported. The single device exhibits unusual properties of organic resonant tunneling diode (ORTD) at low driving voltage region and offers light emission at high voltage. For ORTD, a strong negative differential resistance behavior is demonstrated at room temperature. The current resonance with the peak-to-valley current ratio of over 4.6 and narrow linewidth of only ,1.4,V is achieved. A detailed operating mechanism of the charging and emission modes is proposed, which can be discussed in terms of the strong charge-trapping effect of Ag nanoparticles. The repeatable operations of hybrid device show the mutual influences between two modes and the light emission properties of the ORTD are also discussed. [source]

Noninvasive Semiconductor Field Imaging: Imaging the Electric-Field Distribution in Organic Devices by Confocal Electroreflectance Microscopy (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 8 2009
Mater.
Noninvasive methods for diagnosis of organic devices are based on optical probes. At Politecnico di Milano, M. Celebrano et al. have developed a new method to optically map the electric field inside organic planar devices, as described on page 1180. Their technique involves the combination of electroreflectance spectroscopy with confocal microscopy to achieve high spatial resolution. The cover image shows an artistic impression of the optical probing of a CuPcF16 -based device. [source]

Imaging the Electric-Field Distribution in Organic Devices by Confocal Electroreflectance Microscopy

ADVANCED FUNCTIONAL MATERIALS, Issue 8 2009
Michele Celebrano
Abstract Space resolved Stark spectroscopy is introduced as a non invasive optical technique for imaging electric field distribution in organic semiconductors. Stark spectroscopy relies on the electric field induced change in the absorption/reflection. It is shown that local monitoring of Stark shift with confocal spatial resolution provides quantitative information on the strength of the local field as well as charge distribution within the transport channel. [source]

High Definition Digital Fabrication of Active Organic Devices by Molecular Jet Printing,

ADVANCED FUNCTIONAL MATERIALS, Issue 15 2007
J. Chen
Abstract We introduce a high resolution molecular jet (MoJet) printing technique for vacuum deposition of evaporated thin films and apply it to fabrication of 30,,m pixelated (800,ppi) molecular organic light emitting devices (OLEDs) based on aluminum tris(8-hydroxyquinoline) (Alq3) and fabrication of narrow channel (15,,m) organic field effect transistors (OFETs) with pentacene channel and silver contacts. Patterned printing of both organic and metal films is demonstrated, with the operating properties of MoJet-printed OLEDs and OFETs shown to be comparable to the performance of devices fabricated by conventional evaporative deposition through a metal stencil. We show that the MoJet printing technique is reconfigurable for digital fabrication of arbitrary patterns with multiple material sets and high print accuracy (of better than 5,,m), and scalable to fabrication on large area substrates. Analogous to the concept of "drop-on-demand" in Inkjet printing technology, MoJet printing is a "flux-on-demand" process and we show it capable of fabricating multi-layer stacked film structures, as needed for engineered organic devices. [source]

Vertical-type organic device using thin-film ZnO transparent electrode

ELECTRICAL ENGINEERING IN JAPAN, Issue 2 2007
Hiroyuki Iechi
Abstract We propose a double heterojunction organic light-emitting diode (OLED) using a zinc oxide (ZnO) film, which works as a transparent and electron injection layer. The crystal structure of the ZnO films as a function of Ar/O2 flow ratio and the basic characteristics of the OLED depending on the ZnO sputtering conditions are investigated. Excellent characteristics of the novel OLED were obtained, as high as 470 cd/m2 at 22 V and 7.6 mA/cm2. The results obtained here demonstrate that the vertical organic light-emitting transistor (OLET) using a ZnO layer as an electron injection layer is promising as a key element for flexible sheet displays. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(2): 49,55, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20151 [source]

Noninvasive Semiconductor Field Imaging: Imaging the Electric-Field Distribution in Organic Devices by Confocal Electroreflectance Microscopy (Adv. Funct.

High Definition Digital Fabrication of Active Organic Devices by Molecular Jet Printing,

Surface-Transfer Doping of Organic Semiconductors Using Functionalized Self-Assembled Monolayers,

ADVANCED FUNCTIONAL MATERIALS, Issue 8 2007
W. Chen
Abstract Controlling charge doping in organic semiconductors represents one of the key challenges in organic electronics that needs to be solved in order to optimize charge transport in organic devices. Charge transfer or charge separation at the molecule/substrate interface can be used to dope the semiconductor (substrate) surface or the active molecular layers close to the interface, and this process is referred to as surface-transfer doping. By modifying the Au(111) substrate with self-assembled monolayers (SAMs) of aromatic thiols with strong electron-withdrawing trifluoromethyl (CF3) functional groups, significant electron transfer from the active organic layers (copper(II) phthalocyanine; CuPc) to the underlying CF3 -SAM near the interface is clearly observed by synchrotron photoemission spectroscopy. The electron transfer at the CuPc/CF3 -SAM interface leads to an electron accumulation layer in CF3 -SAM and a depletion layer in CuPc, thereby achieving p-type doping of the CuPc layers close to the interface. In contrast, methyl (CH3)-terminated SAMs do not display significant electron transfer behavior at the CuPc/CH3 -SAM interface, suggesting that these effects can be generalized to other organic-SAM interfaces. Angular-dependent near-edge X-ray absorption fine structure (NEXAFS) measurements reveal that CuPc molecules adopt a standing-up configuration on both SAMs, suggesting that interface charge transfer has a negligible effect on the molecular orientation of CuPc on various SAMs. [source]

Magnetic-Field Effects in Organic Semiconducting Materials and Devices

ADVANCED MATERIALS, Issue 14-15 2009
Bin Hu
Abstract It has been experimentally discovered that a low magnetic field (less than 500 mT) can substantially change the electroluminescence, photoluminescence, photocurrent, and electrical-injection current in nonmagnetic organic semiconducting materials, leading to magnetic-field effects (MFEs). Recently, there has been significant driving force in understanding the fundamental mechanisms of magnetic responses from nonmagnetic organic materials because of two potential impacts. First, MFEs can be powerful experimental tools in revealing and elucidating useful and non-useful excited processes occurring in organic electronic, optical, and optoelectronic devices. Second, MFEs can lead to the development of new multifunctional organic devices with integrated electronic, optical, and magnetic properties for energy conversion, optical communication, and sensing technologies. This progress report discusses magnetically sensitive excited states and charge-transport processes involved in MFEs. The discussions focus on both fundamental theories and tuning mechanisms of MFEs in nonmagnetic organic semiconducting materials. [source]

Electrical Scanning Probe Microscopy on Active Organic Electronic Devices

ADVANCED MATERIALS, Issue 1 2009
Liam S. C. Pingree
Abstract Polymer- and small-molecule-based organic electronic devices are being developed for applications including electroluminescent displays, transistors, and solar cells due to the promise of low-cost manufacturing. It has become clear that these materials exhibit nanoscale heterogeneities in their optical and electrical properties that affect device performance, and that this nanoscale structure varies as a function of film processing and device-fabrication conditions. Thus, there is a need for high-resolution measurements that directly correlate both electronic and optical properties with local film structure in organic semiconductor films. In this article, we highlight the use of electrical scanning probe microscopy techniques, such as conductive atomic force microscopy (c-AFM), electrostatic force microscopy (EFM), scanning Kelvin probe microscopy (SKPM), and similar variants to elucidate charge injection/extraction, transport, trapping, and generation/recombination in organic devices. We discuss the use of these tools to probe device structures ranging from light-emitting diodes (LEDs) and thin-film transistors (TFT), to light-emitting electrochemical cells (LECs) and organic photovoltaics. [source]

High-Mobility C60 Field-Effect Transistors Fabricated on Molecular- Wetting Controlled Substrates,

ADVANCED MATERIALS, Issue 13 2006
K. Itaka
An atomically flat pentacene monomolecular layer remarkably improved the crystallinity of C60 films, thus enhancing the field-effect mobilities in C60 transistors (FETs) (see figure). They showed a four to five times better performance over devices with C60 films grown without a pentacene buffer. Molecular-wetting-controlled substrates can thus offer a general solution to the fabrication of high-performance crystalline organic devices. [source]

Analysis and modeling of organic devices

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2004
Y. Roichman
Abstract We present self consistent picture of charge injection and transport in low mobility disordered organic based devices. We demonstrate the importance of accounting for charge density effects in both modeling and analysis of devices. We outline a method for the analysis of LEDs and FETs. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Triplet Excitation Scavenging in Films of Conjugated Polymers

CHEMPHYSCHEM, Issue 7 2009
Sarah Schols
Abstract Nonvertical triplet energy transfer in solid conjugated polymer films is demonstrated for the first time using 1,3,5,7-cyclooctatetraene, a compound that can efficiently quench the phosphorescence of polyfluorene without affecting its fluorescence (see spectra). The results suggest that nonvertical triplet scavengers might be promising candidates for controlling the triplet concentration in fluorescent high-brightness organic devices. Phosphorescence and delayed fluorescence of polyfluorene polymer films doped with cyclooctatetraene (COT) and anthracene are studied by means of time-resolved photoluminescence (PL) measurements. The occurrence of an anomalous nonvertical triplet energy transfer in solid conjugated polymer films is demonstrated for the first time employing the "nonvertical" COT triplet acceptor, which appears to behave similarly to conventional vertical triplet acceptors, such as anthracene. Both dopant molecules are found to efficiently quench the host phosphorescence of the polymer without affecting the host fluorescence,this can be attributed to the large singlet,triplet (S1,T1) splitting of these molecules. This S1,T1 splitting is exceptionally large in COT due to its low-lying relaxed triplet state, which is capable of accepting host triplet excitations. In contrast to anthracene, the triplet lifetime of the COT molecules is reasonably short, thus making a fast deactivation of the triplet excitations possible. This suggests that nonvertical triplet scavengers might be promising candidates for quenching the host triplet excitations in future electrically pumped fluorescence organic lasers, which suffer from excessive triplet-state losses. [source]