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Inverted Bottom-Emitting OLED Device

a bottom-emitting, oled technology, applied in the direction of semiconductor devices, basic electric elements, electrical apparatus, etc., can solve the problems of low electron mobility in organic materials, high resistance of the medium, and the operation of the el device requires a high voltage (>100 volts) to achieve the effect of improving n-type semiconductor compatibility and reducing air sensitivity

Inactive Publication Date: 2011-02-03
GLOBAL OLED TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The patent describes a method for making an OLED device that is simpler and more suitable for integration with n-type semiconductors. The method involves using a stable substrate that is not reactive with the organics, and an electron-transporting layer made of an N-type inorganic semiconductor. This results in a device that is less sensitive to air and has better compatibility with n-type semiconductors. The technical effect of this invention is to provide a more efficient and reliable method for making OLED devices.

Problems solved by technology

Thus, this organic EL medium was highly resistive and the EL device required an extremely high voltage (>100 volts) to operate.
One inherent drawback of the organic EL devices is that electron mobility in organic materials is extremely low, so that a high voltage is required to produce a strong electric field.
The thickness of the organic medium can be reduced to lower the voltage level required for device operation, but the reduction results in low quantum efficiency due to radiative quenching by a conducting surface, high leakage current, or device shorting.
A problem with this approach is that the organic materials tend to be very fragile and reactive, and can therefore be damaged by the conditions necessary to apply zinc oxide.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

Comparative

[0044]An OLED device was constructed in the following manner:[0045]1. A clean glass substrate with an ITO pattern was placed in a vacuum chamber and evacuated to 5×10−6 torr.[0046]2. The above-prepared substrate was treated by vacuum depositing a 60 nm including 94% 2-phenyl-9,10-bis(2-naphthyl)anthracene (PBNA) as host with 2% 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB, a red dopant) as a light-emitting layer.[0047]3. The above-prepared substrate was further treated by vacuum-depositing a 120 nm layer of 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) as a hole-transporting layer.[0048]4. The above-prepared substrate was further treated by vacuum-depositing a 10 nm layer of hexacyanohexaazatriphenylene (CHATP) as a hole-injecting layer (HIL).

[0049]5. A 60 nm silver anode layer was deposited onto the sample by vacuum evaporation.

example 2

Inventive

[0050]An OLED device was constructed as described in Example 1, except that the following step was added between Steps 1 and 2:[0051]1a. A 40 nm layer of unpatterned ZnO was deposited uniformly on the substrate.

[0052]After deposition, a positive voltage was applied to the top (anode) electrode and a negative voltage to the bottom (cathode) electrode at a constant current of 20 ma / cm2. Any spectral output was measured. Example 1, the comparative example did not emit. Inventive Example 2 emitted orange light with a spectral maximum at 593 nm wavelength and a luminance of 61 candela / m2. This shows that the zinc oxide layer, which is an electron-transporting layer, enables this device to function.

example 3

Comparative

[0053]An OLED device was constructed in the following manner:[0054]1. A clean glass substrate with an ITO pattern was placed in a vacuum chamber and evacuated to 5×10−6 torr.[0055]2. The above-prepared substrate was treated by vacuum depositing a 40 nm PBNA layer with 0.75% green-emitting dopant GED-1 as a light-emitting layer.

[0056]3. The above-prepared substrate was further treated by vacuum-depositing a 75 nm layer of NPB as a hole-transporting layer.[0057]4. A 10 nm hole-injecting layer of CHATP was vacuum-deposited onto the substrate at a coating station.[0058]5. A 40 nm silver anode layer was deposited onto the sample by vacuum evaporation.[0059]6. A 30 nm aluminum conductive protective layer was deposited onto the sample by vacuum evaporation.

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PUM

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Abstract

A method of making an inverted bottom-emitting OLED device, comprising: providing a substrate; providing one or more first electrodes driven by n-type transistors on the substrate; providing an electron-transporting layer over the substrate and first electrode(s), wherein the electron-transporting layer comprises an n-type inorganic semiconductive material with a resistivity in the range of 1 to 105 ohm-cm and a bandgap greater than 2.5 eV; providing an organic light-emitting layer over the electron-transporting layer; providing a hole-transporting layer over the organic emitting layer; and providing a second electrode over the hole-transporting layer.

Description

FIELD OF THE INVENTION[0001]The present invention relates to forming an OLED device with efficient electron transport.BACKGROUND OF THE INVENTION[0002]Organic electroluminescent (EL) devices are known to be highly efficient and are capable of producing a wide range of colors. Useful applications such as flat-panel displays have been contemplated. Representative of earlier organic EL devices are Gurnee et al U.S. Pat. No. 3,172,862; Gurnee U.S. Pat. No. 3,173,050; Dresner, “Double Injection Electroluminescence in Anthracene,” RCA Review, Vol. 30, pp. 322-334, 1969; and Dresner U.S. Pat. No. 3,710,167. Typical organic emitting materials were formed of a conjugated organic host material and a conjugated organic activating agent having condensed benzene rings. The organic emitting material was present as a single layer medium having a thickness much above 1 micrometer. Thus, this organic EL medium was highly resistive and the EL device required an extremely high voltage (>100 volts) ...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H01L51/50
CPCH01L27/3262H01L51/5048H01L51/005H10K59/1213H10K85/60H10K50/14
Inventor TUTT, LEE W.FELLER, THERESE M.COWDERY-CORVAN, PETER J.
Owner GLOBAL OLED TECH
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