Symmetrically Configured AC Light-Emitting (Scale) Devices: Generalizations and Variations

ABSTRACTMost conjugated polymer-based light-emitting devices have been shown to be tunnel diodes which can only operate under forward DC driving field. Recently we have reported the fabrication of symmetrically configured AC light-emitting (SCALE) devices based on heterocyclic aromatic conjugated polymers. By adding an “insulating” layer (e.g. emeraldine base (EB) form of polyaniline) on both sides of the emitting layer, the SCALE devices emit light under both forward and reverse DC bias as well as AC driving voltage. The SCALE device structure ITO/J/emitterFl/M, has been shown to be quite general, and can be applied to a variety of electroluminescent polymers (emitter), insulating polymers (I) and electrode materials (M). Here we summarize and compare the performance of SCALE devices fabricated with different emitter, insulator, and electrode materials. The role of the insulating layer in the SCALE device operation is examined and a model that emphasizing the interface states is proposed to account for the device operation.

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The influence of the Rubrene thickness on the performance of white organic light-emitting devices

Materials Express ◽

10.1166/mex.2020.1655 ◽

2020 ◽

Vol 10 (3) ◽

pp. 384-388

Author(s):

Lina Zhao ◽

Xin Jiang ◽

Jihui Lang ◽

Wenlong Jiang ◽

Gang Zhang ◽

...

Keyword(s):

White Light ◽

Maximum Efficiency ◽

Driving Voltage ◽

Device Structure ◽

Light Emitting ◽

Light Emitting Devices ◽

Organic Light ◽

Organic Light Emitting Devices ◽

Object Material ◽

20 Nm

A group of white OLEDs (organic light-emitting devices), were fabricated using the blue yellow complementary principle. Among them, MCP(1,3-Bis(carbazol-9-yl)benzene) was used as the main material for the blue light layer, FIrPic(Bis(3,5-difluoro)-2-(2-pyridyl)phenyl-(2-carboxypyridyl)iridium(III)) as the phosphorescent object material, and Rubrene(5,6,11,12-Tetraphenylnaphthacene) as the fluorescent material for the yellow light layer. The device structure is NPB(N,N′-Bis(naphthalen-1-yl)-N,N′-bis(phenyl)-benzidine) (20 nm)/Rubrene (0.5 nm)/MCP (3 nm)/MCP: FIrPic (30 nm, 10%)/Rubrene (z nm)/TPBi(1,3,5-Tris(1-phenyl-1Hbenzimidazol-2-yl) benzene)(10 nm)/Alq3(20 nm/LiF (0.6 nm)/Al (100 nm). By adjusting the thickness of Rubrene, the structure of the device was optimized and the performance of the device was improved. When the thickness of Rubrene was 0.5 nm, the performance of the device was the best, the maximum efficiency was 6.41 cd/A, the maximum luminance was 8344 cd/m2. When the driving voltage changed from 5 V to 14 V, the device changed from warm white light to cold white light.

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Fabrication of Micro-OLEDs by Room-temperature Curing Nanocontact-print Lithography Using DLC Molds

MRS Proceedings ◽

10.1557/opl.2012.1711 ◽

2012 ◽

Vol 1511 ◽

Cited By ~ 1

Author(s):

Ippei Ishikawa ◽

Keisuke Sakurai ◽

Shuji Kiyohara ◽

Taisuke Okuno ◽

Hideto Tanoue ◽

...

Keyword(s):

Indium Tin Oxide ◽

Nanoimprint Lithography ◽

Room Temperature ◽

Hole Transport ◽

Transport Layer ◽

Electron Transport Layer ◽

Insulating Layer ◽

Light Emitting ◽

Light Emitting Devices ◽

Ito Glass

ABSTRACTThe microfabrication technologiesfor organic light-emitting devices (OLEDs) are essential to the fabrication of the next generation of light-emitting devices. The micro-OLEDs fabricated by room-temperature curing nanoimprint lithography (RTC-NIL) using diamond molds have been investigated. However, light emissions from 10 μm-square-dot OLEDs fabricated by the RTC-NIL method have not been uniform. Therefore, we proposed the fabrication of micro-OLEDs by room-temperature curing nanocontact-print lithography (RTC-NCL) using the diamond-like carbon (DLC) mold. The DLC molds used in RTC-NCL were fabricated by an electron cyclotron resonance (ECR) oxygen ion shower with polysiloxane oxide mask in electron beam (EB) lithography technology. The mold patterns are square and rectangle dots which has 10 µm-width, 10 µm-width and50 µm-length, respectively. The height of the patterns is 500 nm. The DLC molds were used to form the insulating layer of polysiloxane in RTC-NCL. We carried out the RTC-NCL process using the DLC mold under the following optimum conditions: 0.1 MPa-pressure for coating DLC mold with polysiloxane film, 2.1 MPa-pressure for transferring polysiloxane from DLC mold pattern to indium tin oxide (ITO) glass substrate. We deposited N, N'-Diphenyl -N, N'-di (m-tolyl)benzidine (TPD) [40 nm-thickness] as hole transport layer / Tris(8-quinolinolato)aluminum (Alq3) [40 nm-thickness] as electron transport layer / Al [200 nm-thickness] as cathode on ITO glass substrateas anode in this order. We succeeded in formation of the insulating layer with square and rectangle dots which has 10 µm-width,10 µm-width and 50 µm-length, and operation of micro-OLEDs by RTC-NIL using DLC molds.

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Visible Light Emission from Erbium Doped Yttria Stabilized Zirconia

MRS Proceedings ◽

10.1557/proc-789-n11.8 ◽

2003 ◽

Vol 789 ◽

Cited By ~ 3

Author(s):

Michael Cross ◽

Walter Varhue

Keyword(s):

Band Gap ◽

Light Emission ◽

Green Light ◽

Yttria Stabilized Zirconia ◽

Stabilized Zirconia ◽

Rare Earth Ion ◽

Device Structure ◽

Insulating Layer ◽

Light Emitting ◽

Erbium Doped

ABSTRACT: One of the major shortcomings of silicon (Si) as a semiconductor material is its inability to yield efficient light emission. There has been a continued interest in adding rare earth ion impurities such as erbium (Er) to the Si lattice to act as light emitting centers. The low band gap of Si however has complicated this practice by quenching and absorbing this possible emission. Increasing the band gap of the host has been successfully tried in the case of gallium nitride (GaN) [1] and Si-rich oxide (SRO) [2] alloys. A similar approach has been tried here, where Er oxide (ErOx) nanocrystals have been formed in a yttria stabilized zirconia (YSZ) host deposited on a Si (100) substrate. The YSZ is deposited as a heteroepitaxial, insulating layer on the Si substrate by a reactive sputtering technique. The Er is also incorporated by a sputtering process from a metallic target and its placement in the YSZ host can be easily controlled. The device structure formed is a simple metal contact/insulator/phosphor sandwich. The device has been found to emit visible green light at low bias voltages. The advantage of this material is that it is much more structured than SiO2 which can theoretically lead to higher emission intensity.

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Silicon Quantum Dot Light Emitting Diode at 620 nm

Micromachines ◽

10.3390/mi10050318 ◽

2019 ◽

Vol 10 (5) ◽

pp. 318 ◽

Cited By ~ 8

Author(s):

Hiroyuki Yamada ◽

Naoto Shirahata

Keyword(s):

Quantum Dot ◽

High Performance ◽

Light Emitting Diode ◽

Optically Active ◽

Driving Voltage ◽

Device Structure ◽

Light Emitting ◽

Naked Eye ◽

Turn On ◽

Silicon Quantum Dot

Here we report a quantum dot light emitting diode (QLED), in which a layer of colloidal silicon quantum dots (SiQDs) works as the optically active component, exhibiting a strong electroluminescence (EL) spectrum peaking at 620 nm. We could not see any fluctuation of the EL spectral peak, even in air, when the operation voltage varied in the range from 4 to 5 V because of the possible advantage of the inverted device structure. The pale-orange EL spectrum was as narrow as 95 nm. Interestingly, the EL spectrum was narrower than the corresponding photoluminescence (PL) spectrum. The EL emission was strong enough to be seen by the naked eye. The currently obtained brightness (∼4200 cd/m2), the 0.033% external quantum efficiency (EQE), and a turn-on voltage as low as 2.8 V show a sufficiently high performance when compared to other orange-light-emitting Si-QLEDs in the literature. We also observed a parasitic emission from the neighboring compositional layer (i.e., the zinc oxide layer), and its intensity increased with the driving voltage of the device.

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Investigations on the Aluminum/Para-Hexaphenyl Interface in Light Emitting Devices

MRS Proceedings ◽

10.1557/proc-488-509 ◽

1997 ◽

Vol 488 ◽

Cited By ~ 4

Author(s):

N. Koch ◽

L.-M. Yu ◽

J.-L. Guyaux ◽

Y. Morciaux ◽

G. Leising ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Active Material ◽

Direct Interaction ◽

Metal Electrode ◽

Insulating Layer ◽

Aluminum Films ◽

Light Emitting ◽

Light Emitting Devices ◽

Thin Aluminum

AbstractBlue light emitting devices (LED) with para-hexaphenyl (PHP) as the active material and aluminum as cathode exhibit very high quantum efficiencies. To further optimize device performance it is crucial to understand the physical properties of the involved interfaces. We have performed Rutherford-Backscattering experiments on actual devices to show the importance of oxygen in the interface formation at the cathode as this leads to the formation of a layer of AlxOy between PHP and aluminum. In devices, where the organic film is exposed to air before the metal electrode is evaporated, an insulating layer on the metal-side therefore is inherent. It has been shown that the introduction of an intermediate layer between active material and electrodes results in a higher quantum efficiency of the LED, the most common concepts being charge-transport-layers, or insulators on the other hand. Our results underline the need for a better control of the LED processing. Ultraviolet- and X-ray photoelectron spectroscopy in situ growth studies of thin aluminum films on PHP have been made to reveal the change in the electronic structure of the active medium in a LED in the absence of oxygen. Also the direct interaction of oxygen with this organic material is investigated by photoelectron spectroscopy.

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All-inorganic Light Emitting Devices Based on Semiconducting Nanoparticles

MRS Proceedings ◽

10.1557/proc-1260-t09-02 ◽

2010 ◽

Vol 1260 ◽

Author(s):

Ekaterina Neshataeva ◽

Tilmar Kümmell ◽

André Ebbers ◽

Gerd Bacher

Keyword(s):

Spectral Range ◽

Zno Nanoparticles ◽

Hole Injection ◽

Light Emitting ◽

Light Emitting Devices ◽

Layer Sequence ◽

Current Densities ◽

The Stability ◽

P Type ◽

Device Operation

AbstractWe demonstrate light emitting devices based on ZnO nanoparticles and realized without any additional organic support layers. Pure ZnO devices showed electroluminescence in the visible and the UV spectral range at voltages below 10 V. In order to facilitate hole injection and to stabilize device operation, additional p-type inorganic support layers were introduced. Sputtered NiO layers are shown to improve the stability of the device and its I/V behavior. First bilayer devices consisting of a layer sequence of p-doped Si and naturally n-doped ZnO nanoparticles revealed promising electro-luminescence results with a high contribution in the UV spectral range at reduced current densities.

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Efficient Biopolymer Blue Organic Light-Emitting Devices with Low Driving Voltage

Japanese Journal of Applied Physics ◽

10.1143/jjap.51.031601 ◽

2012 ◽

Vol 51 ◽

pp. 031601

Author(s):

I-Ching Chen ◽

Yi-Wen Chiu ◽

Yu-Chueh Hung

Keyword(s):

Driving Voltage ◽

Light Emitting ◽

Light Emitting Devices ◽

Organic Light ◽

Organic Light Emitting Devices

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New Dendritic Materials as Potential OLED Transport and Emitter Moeities

MRS Proceedings ◽

10.1557/proc-621-q3.9.1 ◽

2000 ◽

Vol 621 ◽

Cited By ~ 4

Author(s):

Asanga B. Padmaperuma ◽

Greg Schmett ◽

Daniel Fogarty ◽

Nancy Washton ◽

Sanjini Nanayakkara ◽

...

Keyword(s):

Failure Modes ◽

The Other ◽

Thermal Stabilities ◽

Dual Purpose ◽

Light Emitting ◽

Light Emitting Devices ◽

Organic Layers ◽

Organic Light ◽

Hole Transporting ◽

Device Operation

Traditionally, organic light-emitting devices (OLEDs) are prepared with discrete layers for hole and electron transport. Different materials must be used for these layers because most materials will preferentially transport one charge carrier more efficiently than the other. In most cases, the emitter material serves a dual purpose as both the emitter and the hole or electron transporter. One of the major failure modes of OLEDs results from thermal instabilities of the insulating organic layers caused by joule heating during device operation. The problem is most pronounced for the hole transporting layer (HTL) material which are usually tertiary aromatic amines (i.e., TPD and NPD). This has been attributed to the relatively lower glass transition temperatures (Tg) and resulting inferior thermal stabilities compared to the other materials making up the device. Many researchers have produced HTL materials with higher Tgs based on tertiary aromatic amine oligomers and starburst compounds. Starburst or model dendritic materials offer the advantages of high thermal stabilities and multi-functionality.

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