15,688 research outputs found
A solution processed flexible nanocomposite electrode with efficient light extraction for organic light emitting diodes.
Highly efficient organic light emitting diodes (OLEDs) based on multiple layers of vapor evaporated small molecules, indium tin oxide transparent electrode, and glass substrate have been extensively investigated and are being commercialized. The light extraction from the exciton radiative decay is limited to less than 30% due to plasmonic quenching on the metallic cathode and the waveguide in the multi-layer sandwich structure. Here we report a flexible nanocomposite electrode comprising single-walled carbon nanotubes and silver nanowires stacked and embedded in the surface of a polymer substrate. Nanoparticles of barium strontium titanate are dispersed within the substrate to enhance light extraction efficiency. Green polymer OLED (PLEDs) fabricated on the nanocomposite electrode exhibit a maximum current efficiency of 118â
cd/A at 10,000â
cd/m(2) with the calculated external quantum efficiency being 38.9%. The efficiencies of white PLEDs are 46.7â
cd/A and 30.5%, respectively. The devices can be bent to 3â
mm radius repeatedly without significant loss of electroluminescent performance. The nanocomposite electrode could pave the way to high-efficiency flexible OLEDs with simplified device structure and low fabrication cost
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Manufacturing flexible light-emitting polymer displays with conductive lithographic film technology
We report on a new low-cost manufacturing process for flexible displays that has the potential to rapidly expand the market into areas that have traditionally been outside the scope of such technology. In this paper we consider the feasibility of using offset-lithography to deposit contacts for polymer light-emitting displays. We compare and contrast manufacturing criteria and present a case study detailing our initial results. It is expected that these developments will stimulate further progress in multilayer device
fabrication.
Cheap, flexible conductive interconnects have the potential to find applications in a wide variety of device structures. For the more challenging exploitation areas in multilayer devices, such as displays, it was found that the properties of conductive lithographic films were not optimal in their current form. Three parameters (conductivity, surface roughness and surface work function) were identified as critical to device fabrication. Calendering and electroless plating were investigated as methods to improve these properties. Both methods aimed to modify the surface roughness and conductivity, with the plating study also modifying the work function
Enhanced light emission from top-emitting organic light-emitting diodes by optimizing surface plasmon polariton losses
We demonstrate enhanced light extraction for monochrome top-emitting organic
light-emitting diodes (OLEDs). The enhancement by a factor of 1.2 compared to a
reference sample is caused by the use of a hole transport layer (HTL) material
possessing a low refractive index (1.52). The low refractive index reduces the
in-plane wave vector of the surface plasmon polariton (SPP) excited at the
interface between the bottom opaque metallic electrode (anode) and the HTL. The
shift of the SPP dispersion relation decreases the power dissipated into lost
evanescent excitations and thus increases the outcoupling efficiency, although
the SPP remains constant in intensity. The proposed method is suitable for
emitter materials owning isotropic orientation of the transition dipole moments
as well as anisotropic, preferentially horizontal orientation, resulting in
comparable enhancement factors. Furthermore, for sufficiently low refractive
indices of the HTL material, the SPP can be modeled as a propagating plane wave
within other organic materials in the optical microcavity. Thus, by applying
further extraction methods, such as micro lenses or Bragg gratings, it would
become feasible to obtain even higher enhancements of the light extraction.Comment: 11 pages, 6 figures, will be submitted to PR
Solution-Processable Graphene Oxide as an Efficient Hole Injection Layer for High Luminance Organic Light-Emitting Diodes
The application of solution-processable graphene oxide (GO) as hole injection
layer in organic light-emitting diodes (OLEDs) is demonstrated. High luminance
of over 53,000 cd m-2 is obtained at only 10 V. The results will unlock a route
of applying GO in flexible OLEDs and other electrode applications.Comment: 14 pages, 3 figures, 1 tabl
Discovery of two new phases of zirconium tetrakis(8-hydroxyquinolinolate): synthesis, crystal structure and their electron transporting characteristics in organic light emitting diodes (OLEDs)
Two new phases of zirconium tetrakis(8-hydroxyquinolinolate) (Zrq4) have been synthesised and characterised by single crystal X-ray diffraction. Their electrical, electronic, optical and thermal properties have been studied. Their electron transporting characteristics have been investigated in organic light emitting devices where the two phases show remarkable differences in performance. One of the forms (designated a-Zrq4) gives significantly lower operating voltage, higher efficiencies and longer lifetime than the other (designated b-Zrq4) in organic light emitting devices.EPSR
Facile fabrication of stretchable Ag nanowire/polyurethane electrodes using high intensity pulsed light
Silver nanowires (AgNWs) have emerged as a promising nanomaterial for next generation stretchable electronics. However, until now, the fabrication of AgNW-based components has been hampered by complex and time-consuming steps. Here, we introduce a facile, fast, and one-step methodology for the fabrication of highly conductive and stretchable AgNW/polyurethane (PU) composite electrodes based on a high-intensity pulsed light (HIPL) technique. HIPL simultaneously improved wire-wire junction conductivity and wire-substrate adhesion at room temperature and in air within 50 mu s, omitting the complex transfer-curing-implanting process. Owing to the localized deformation of PU at interfaces with AgNWs, embedding of the nanowires was rapidly carried out without substantial substrate damage. The resulting electrode retained a low sheet resistance (high electrical conductivity) of <10 Omega/sq even under 100% strain, or after 1,000 continuous stretching-relaxation cycles, with a peak strain of 60%. The fabricated electrode has found immediate application as a sensor for motion detection. Furthermore, based on our electrode, a light emitting diode (LED) driven by integrated stretchable AgNW conductors has been fabricated. In conclusion, our present fabrication approach is fast, simple, scalable, and cost-efficient, making it a good candidate for a future roll-to-roll process
Charge transport in nanoscale vertical organic semiconductor pillar devices
We report charge transport measurements in nanoscale vertical pillar
structures incorporating ultrathin layers of the organic semiconductor
poly(3-hexylthiophene)(P3HT). P3HT layers with thickness down to 5 nm are
gently top-contacted using wedging transfer, yielding highly reproducible,
robust nanoscale junctions carrying high current densities (up to
A/m). Current-voltage data modeling demonstrates excellent hole injection.
This work opens up the pathway towards nanoscale, ultrashort-channel organic
transistors for high-frequency and high-current-density operation.Comment: 30 pages, 8 figures, 1 tabl
Recent advances in solid-state organic lasers
Organic solid-state lasers are reviewed, with a special emphasis on works
published during the last decade. Referring originally to dyes in solid-state
polymeric matrices, organic lasers also include the rich family of organic
semiconductors, paced by the rapid development of organic light emitting
diodes. Organic lasers are broadly tunable coherent sources are potentially
compact, convenient and manufactured at low-costs. In this review, we describe
the basic photophysics of the materials used as gain media in organic lasers
with a specific look at the distinctive feature of dyes and semiconductors. We
also outline the laser architectures used in state-of-the-art organic lasers
and the performances of these devices with regard to output power, lifetime,
and beam quality. A survey of the recent trends in the field is given,
highlighting the latest developments in terms of wavelength coverage,
wavelength agility, efficiency and compactness, or towards integrated low-cost
sources, with a special focus on the great challenges remaining for achieving
direct electrical pumping. Finally, we discuss the very recent demonstration of
new kinds of organic lasers based on polaritons or surface plasmons, which open
new and very promising routes in the field of organic nanophotonics
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