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Researchers Submit Patent Application, "High Resolution Low Power Consumption Oled Display with Extended Lifetime", for Approval

August 21, 2014



By a News Reporter-Staff News Editor at Politics & Government Week -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors Hack, Michael (Princeton, NJ); Weaver, Michael Stuart (Princeton, NJ); Brown, Julia J. (Yardley, PA); Xu, Xin (West Windsor, NJ), filed on April 2, 2014, was made available online on August 7, 2014.

The patent's assignee is Universal Display Corporation.

News editors obtained the following quote from the background information supplied by the inventors: "Opto-electronic devices that make use of organic materials are becoming increasingly desirable for a number of reasons. Many of the materials used to make such devices are relatively inexpensive, so organic opto-electronic devices have the potential for cost advantages over inorganic devices. In addition, the inherent properties of organic materials, such as their flexibility, may make them well suited for particular applications such as fabrication on a flexible substrate. Examples of organic opto-electronic devices include organic light emitting devices (OLEDs), organic phototransistors, organic photovoltaic cells, and organic photodetectors. For OLEDs, the organic materials may have performance advantages over conventional materials. For example, the wavelength at which an organic emissive layer emits light may generally be readily tuned with appropriate dopants.

"OLEDs make use of thin organic films that emit light when voltage is applied across the device. OLEDs are becoming an increasingly interesting technology for use in applications such as flat panel displays, illumination, and backlighting. Several OLED materials and configurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and 5,707,745, which are incorporated herein by reference in their entirety.

"One application for phosphorescent emissive molecules is a full color display. Industry standards for such a display call for pixels adapted to emit particular colors, referred to as 'saturated' colors. In particular, these standards call for saturated red, green, and blue pixels. Color may be measured using CIE coordinates, which are well known to the art.

"One example of a green emissive molecule is tris(2-phenylpyridine)iridium, denoted Ir(ppy)3, which has the following structure:

"##STR00001##

"In this, and later figures herein, we depict the dative bond from nitrogen to metal (here, Ir) as a straight line.

"As used herein, the term 'organic' includes polymeric materials as well as small molecule organic materials that may be used to fabricate organic opto-electronic devices. 'Small molecule' refers to any organic material that is not a polymer, and 'small molecules' may actually be quite large. Small molecules may include repeat units in some circumstances. For example, using a long chain alkyl group as a substituent does not remove a molecule from the 'small molecule' class. Small molecules may also be incorporated into polymers, for example as a pendent group on a polymer backbone or as a part of the backbone. Small molecules may also serve as the core moiety of a dendrimer, which consists of a series of chemical shells built on the core moiety. The core moiety of a dendrimer may be a fluorescent or phosphorescent small molecule emitter. A dendrimer may be a 'small molecule,' and it is believed that all dendrimers currently used in the field of OLEDs are small molecules.

"As used herein, 'top' means furthest away from the substrate, while 'bottom' means closest to the substrate. Where a first layer is described as 'disposed over' a second layer, the first layer is disposed further away from substrate. There may be other layers between the first and second layer, unless it is specified that the first layer is 'in contact with' the second layer. For example, a cathode may be described as 'disposed over' an anode, even though there are various organic layers in between. As used herein, two layers or regions may be described as being disposed in a 'stack' when at least a portion of one layer or region is disposed over at least a portion of the other.

"As used herein, 'solution processible' means capable of being dissolved, dispersed, or transported in and/or deposited from a liquid medium, either in solution or suspension form.

"A ligand may be referred to as 'photoactive' when it is believed that the ligand directly contributes to the photoactive properties of an emissive material. A ligand may be referred to as 'ancillary' when it is believed that the ligand does not contribute to the photoactive properties of an emissive material, although an ancillary ligand may alter the properties of a photoactive ligand.

"As used herein, and as would be generally understood by one skilled in the art, a first 'Highest Occupied Molecular Orbital' (HOMO) or 'Lowest Unoccupied Molecular Orbital' (LUMO) energy level is 'greater than' or 'higher than' a second HOMO or LUMO energy level if the first energy level is closer to the vacuum energy level. Since ionization potentials (IP) are measured as a negative energy relative to a vacuum level, a higher HOMO energy level corresponds to an IP having a smaller absolute value (an IP that is less negative). Similarly, a higher LUMO energy level corresponds to an electron affinity (EA) having a smaller absolute value (an EA that is less negative). On a conventional energy level diagram, with the vacuum level at the top, the LUMO energy level of a material is higher than the HOMO energy level of the same material. A 'higher' HOMO or LUMO energy level appears closer to the top of such a diagram than a 'lower' HOMO or LUMO energy level.

"As used herein, and as would be generally understood by one skilled in the art, a first work function is 'greater than' or 'higher than' a second work function if the first work function has a higher absolute value. Because work functions are generally measured as negative numbers relative to vacuum level, this means that a 'higher' work function is more negative. On a conventional energy level diagram, with the vacuum level at the top, a 'higher' work function is illustrated as further away from the vacuum level in the downward direction. Thus, the definitions of HOMO and LUMO energy levels follow a different convention than work functions.

"Layers, materials, regions, and devices may be described herein in reference to the color of light they emit. In general, as used herein, an emissive region that is described as producing a specific color of light may include one or more emissive layers disposed over each other in a stack.

"As used herein, a 'red' layer, material, or device refers to one that emits light in the range of about 580-700 nm; a 'green' layer, material, or device refers to one that has an emission spectrum with a peak wavelength in the range of about 500-600 nm; a 'blue' layer, material, or device refers to one that has an emission spectrum with a peak wavelength in the range of about 400-500 nm. In some arrangements, separate regions, layers, materials, or devices may provide separate 'deep blue' and a 'light blue' light. As used herein, in arrangements that provide separate 'light blue' and 'deep blue', the 'deep blue' component refers to one having a peak emission wavelength that is at least about 4 nm less than the peak emission wavelength of the 'light blue' component. Typically, a 'light blue' component has a peak emission wavelength in the range of about 465-500 nm, and a 'deep blue' component has a peak emission wavelength in the range of about 400-470 nm, though these ranges may vary for some configurations. Similarly, a color altering layer refers to a layer that converts or modifies another color of light to light having a wavelength as specified for that color. For example, a 'red' color filter refers to a filter that results in light having a wavelength in the range of about 580-700 nm. In general there are two classes of color altering layers: color filters that modify a spectrum by removing unwanted wavelengths of light, and color changing layers that convert photons of higher energy to lower energy.

"More details on OLEDs, and the definitions described above, can be found in U.S. Pat. No. 7,279,704, which is incorporated herein by reference in its entirety."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "Pixel arrangements for light emitting devices are provided, which include sub-pixels that emit not more than two colors and/or not more than two color altering layers. Multiple sub-pixels within a full-color pixel arrangement may emit the same color light initially, which is then converted to one or more other colors by various color filter techniques.

"According to an embodiment, a full-color pixel arrangement for an OLED device includes a plurality of sub-pixels, each of which includes an emissive region. The arrangement may include emissive regions that emit light of not more than two colors, and may include not more than two color altering layers. Each color altering layer may be disposed in a stack with an emissive region associated with a sub-pixel. The sub-pixels, and/or the corresponding emissive regions, may have different physical sizes, and each emissive region may include one or more emissive devices, layers, or materials.

"In an embodiment, a full-color pixel for an OLED device may include a plurality of sub-pixels, including a first sub-pixel having an emissive region configured to emit blue light and a second sub-pixel having an emissive region configured to emit yellow light. The pixel arrangement may include emissive regions of not more than two colors, and/or not more than two color altering layers.

"According to an embodiment, a full-color pixel arrangement for an OLED device may include first, second, and third sub-pixels. The first region may be configured to emit a first color, and the second and third regions each configured to emit a second color. A color altering layer may be disposed in a stack with the second and/or the third emissive region. The arrangement also may include a fourth sub-pixel having an emissive region configured to emit the second color. A third color altering layer, which may provide a color different than those disposed in a stack with the second and/or third emissive regions, also may be disposed in a stack with the fourth emissive region.

"In an embodiment, a full-color OLED pixel arrangement may be fabricated by depositing a first emissive material through a mask over a substrate, and depositing a second emissive material through a mask over the substrate, where the second emissive material is configured to emit a different color than the first emissive material. A first color filter may be disposed in a stack with a portion of the second emissive material. In an embodiment, not more than two masking steps may be used to fabricate the arrangement.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1 shows an organic light emitting device.

"FIG. 2 shows an inverted organic light emitting device that does not have a separate electron transport layer.

"FIG. 3 shows a schematic illustration of an example masking arrangement suitable for fabricating a pixel arrangement as disclosed herein.

"FIG. 4 shows a schematic illustration of a pixel arrangement according to an embodiment disclosed herein.

"FIG. 5 shows a schematic illustration of a pixel arrangement according to an embodiment disclosed herein.

"FIG. 6 shows a schematic illustration of a pixel arrangement according to an embodiment disclosed herein.

"FIG. 7 shows a schematic illustration of an example masking arrangement suitable for fabricating a pixel arrangement as disclosed herein.

"FIG. 8 shows a schematic illustration of a pixel arrangement according to an embodiment disclosed herein.

"FIG. 9 shows a schematic illustration of an example masking arrangement suitable for fabricating a pixel arrangement as disclosed herein.

"FIG. 10 shows a schematic illustration of a pixel arrangement according to an embodiment disclosed herein.

"FIG. 11 shows the 1931 CIE diagram that highlights a set of points outside the RG line according to an embodiment disclosed herein.

"FIG. 12 shows the 1931 CIE diagram with coordinates for pure red, green, and blue, and for a multi-component yellow source that lies outside the RG line according to an embodiment disclosed herein.

"FIG. 13 illustrates an example color point rendered without the use of a red sub-pixel according to an embodiment disclosed herein.

"FIG. 14 shows a CIE diagram that identifies red, green, blue, and yellow points, an established white point, and various color regions according to an embodiment disclosed herein.

"FIG. 15 shows a schematic illustration of a pixel arrangement including a blue color change layer disposed over a blue emissive region according to an embodiment disclosed herein.

"FIG. 16 shows a schematic illustration of a pixel arrangement including a blue color change layer disposed over a blue emissive region according to an embodiment disclosed herein.

"FIG. 17 shows a schematic illustration of a pixel arrangement including a blue color change layer disposed over a blue emissive region according to an embodiment disclosed herein."

For additional information on this patent application, see: Hack, Michael; Weaver, Michael Stuart; Brown, Julia J.; Xu, Xin. High Resolution Low Power Consumption Oled Display with Extended Lifetime. Filed April 2, 2014 and posted August 7, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=5784&p=116&f=G&l=50&d=PG01&S1=20140731.PD.&OS=PD/20140731&RS=PD/20140731

Keywords for this news article include: Universal Display Corporation.

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