News Column

Patent Application Titled "Fine Tuning of Emission Spectra by Combination of Multiple Emitter Spectra" Published Online

May 29, 2014



By a News Reporter-Staff News Editor at Politics & Government Week -- According to news reporting originating from Washington, D.C., by VerticalNews journalists, a patent application by the inventors ADAMOVICH, Vadim (Yardley, PA); YAMAMOTO, Hitoshi (Pennington, NJ); WEAVER, Michael S. (Princeton, NJ), filed on January 9, 2014, was made available online on May 15, 2014.

The assignee for this patent application is Universal Display Corporation.

Reporters 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).sub.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, '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.

"As used herein, and as would be generally understood by one of skill in the art, the term 'emitting' as used to describe a material in a device refers to a material that emits a significant amount of light when the device is operated under normal conditions. For example, Ir(ppy).sub.3 is a well known emissive organic material. Ir(ppy).sub.3 may be used as an emitting material in an OLED, generally by including it in the emissive layer with a host, in a device designed such that recombination occurs in or near the layer containing Ir(ppy).sub.3, and such that emission from the Ir(ppy).sub.3 is energetically favored. However, Ir(ppy).sub.3 may also be used in an OLED as a material that is not an 'emitting' material. For example, it is known to use Ir(ppy).sub.3 as a hole transport material in a hole transport layer, such that the Ir(ppy).sub.3 functions to transport holes to an emissive layer where a different material emits light. In this context, Ir(ppy).sub.3 is not considered an 'emitting' material.

"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."

In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventors' summary information for this patent application: "A first device is provided. The first device includes an anode, a cathode and an emissive layer disposed between the anode and the cathode. The emissive layer includes a first organic emitting material having a first peak wavelength and a second organic emitting material having a second peak wavelength. The emissive layer has a homogenous composition. The second peak wavelength is between 0 and 40 nm greater than the first peak wavelength.

"In one embodiment, the first and second organic emitting materials are phosphorescent organic light emitting materials.

"Preferably, the second peak wavelength is between 12 and 28 nm greater than the first peak wavelength.

"In some embodiments, first device of claim 1, the first device emits a third peak wavelength that is between the first peak wavelength and the second peak wavelength. Preferably, the concentration of the first organic emitting material in the emissive layer is C1, the concentration of the second organic emitting material in the emissive layer is C2, the first, second and third peak wavelengths are .lamda.1, .lamda.2, and .lamda.3, respectively, and the third peak wavelength .lamda.3 is within 4% of:

"((.lamda.1 C1)+(.lamda.2 C2))/(C1+C2).

"In some embodiments, wherein the FWHM of the emissive spectrum of the first device is less than the greater of the FWHM of the emissive spectrum of: (i) a second device that is the same as the first device in all respects except that it includes the first emitting material but not the second emitting material, and (ii) a third device that is the same as the first device in all respects except that it includes the second emitting material but not the first emitting material.

"In some embodiments, the measured FWHM of the emissive spectrum of the first device is less than the combined emission of the first and second emitting materials calculated based on the proportions of the first and second emitting materials present in the emissive layer. In some embodiments, the measured FWHM of the emissive spectrum of the first device is at least 10% less than the combined emission of the first and second emitting materials calculated based on the proportions of the first and second emitting materials present in the emissive layer.

"In some embodiments, the first device is an organic light emitting device.

"In some embodiments, the first device is a panel that includes a plurality of organic light emitting devices controlled by an active matrix.

"In some embodiments, the first device is a consumer product.

"A method of fabricating a first device is provided. A first container is provided that contains, in a desired proportion: a first organic emitting material having a first peak wavelength, and a second organic emitting material having a second peak wavelength. A substrate is provided having a first electrode disposed thereon. An emissive layer is deposited over the first electrode, wherein the first container is a source of material for depositing, and wherein the emissive layer comprises the first and second organic emitting materials in the desired proportion. A second electrode over the first emissive layer. The second peak wavelength is between 0 and 40 nm greater than the first peak wavelength.

"In some embodiments, depositing the emissive layer further comprises depositing an organic host along with the first and second organic emitting materials. The organic host may be included in and deposited from the first container, and/or may be deposited from a second container.

"Embodiments and preferences discussed above with respect to devices are also applicable to methods described herein.

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 structure of devices that were fabricated having variable [%] of emitters C and D, used with Example 1.

"FIG. 4 shows electroluminescent (EL) spectra of the devices of Example 1.

"FIG. 5 shows maximum wavelength and full width half maximum (FWHM) values for the devices of Example 1. Both measured experimental data and results calculated by adding spectra proportional to emitter concentration are shown.

"FIG. 6 shows the FWHM difference (experimental vs. calculated) values for the devices of Example 1.

"FIG. 7 shows schematic structure for the devices of Example 2 with variable [%] of emitters A and B.

"FIG. 8 shows EL spectra of the devices of Example 2 with variable [%] of emitters A and B.

"FIG. 9 shows maximum wavelength and FWHM values for the devices in Example 2 with variable [%] of emitters A and B. Both measured experimental data and results calculated by adding spectra proportional to emitter concentration are shown.

"FIG. 10 shows a schematic structure for the devices in Example 3 with variable [%] of emitters B and C.

"FIG. 11 shows EL spectra for the devices of Example 3 with variable [%] of emitters B and C.

"FIG. 12 shows maximum wavelength and FWHM values for the devices of Example 3 with variable [%] of emitters B and C. Both measured experimental data and results calculated by adding spectra proportional to emitter concentration are shown.

"FIG. 13 shows a schematic structure for the devices of Example 4 with variable [%] of emitters A and D.

"FIG. 14 shows EL spectra for the devices of Example 4 with variable [%] of emitters A and D.

"FIG. 15 shows maximum wavelength and FWHM values for the devices of Example 4 with variable [%] of emitters A and D. Both measured experimental data and results calculated by adding spectra proportional to emitter concentration are shown.

"FIG. 16 shows a schematic structure for the devices of Example 5 with variable [%] of emitters B and D.

"FIG. 17 shows EL spectra for the devices of Example 5 with variable [%] of emitters B and D.

"FIG. 18 shows maximum wavelength and FWHM values for the devices of Example 5 with variable [%] of emitters B and D. Both measured experimental data and results calculated by adding spectra proportional to emitter concentration are shown.

"FIG. 19 shows chemical structures for compounds used in device fabrication."

For more information, see this patent application: ADAMOVICH, Vadim; YAMAMOTO, Hitoshi; WEAVER, Michael S. Fine Tuning of Emission Spectra by Combination of Multiple Emitter Spectra. Filed January 9, 2014 and posted May 15, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=2377&p=48&f=G&l=50&d=PG01&S1=20140508.PD.&OS=PD/20140508&RS=PD/20140508

Keywords for this news article include: Universal Display Corporation.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


For more stories covering the world of technology, please see HispanicBusiness' Tech Channel



Source: Politics & Government Week


Story Tools






HispanicBusiness.com Facebook Linkedin Twitter RSS Feed Email Alerts & Newsletters