Patent Application
20140339987
The present invention relates to organic light emitting devices (OLEDs) and, more specifically, to systems including OLED lighting components in communication with remote sensors.
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:
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.
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.
Devices and techniques for generating light having one or more characteristics are provided.
In an embodiment, a system for providing light having a desired characteristic includes a sensor component and a lighting component. The sensor component may include a sensor configured to measure a physical characteristic, and a wireless transmitter configured to provide a sensor signal based upon the physical characteristic, which specifies a desired light characteristic. The lighting component may include an OLED, such as a color-tunable OLED, a wireless receiver configured to receive the sensor signal, and a controller configured to provide a control signal to the OLED. The control signal may specify the desired light characteristic, thus causing the OLED to emit light having the desired light characteristic. The sensor may receive the sensor signal in real-time, and/or the control signal may specify the desired light characteristic in real time based upon the physical characteristic. The desired light characteristic may be, for example, a color, an intensity, a temperature, and/or a pattern.
In an embodiment, a device is provided that includes an OLED, such as a color-tunable OLED, a wireless receiver configured to receive a signal from a remote sensor in real-time, which specifies a desired light characteristic resulting from an automatic measurement, by the sensor, of a physical characteristic measured by the remote sensor in real-time, and a controller configured to provide a control signal to the color-tunable OLED specifying the desired light characteristic in real-time, which causes the color-tunable OLED to emit light having the desired light characteristic.
In an embodiment, the sensor component also may include a reference reflector, such that the physical characteristic is an attribute of light reflected by the reference reflector. The sensor component also may include a reference light source, such that the physical characteristic is an attribute of the reference light reflected by the reference reflector.
In an embodiment, the sensor component may be portable and/or include a battery power source.
In an embodiment, the OLED may be configured to emit light having the desired light characteristic by emitting light of a plurality of colors having an intensity distribution based upon a desired color.
In an embodiment, a system as disclosed may include multiple lighting components, each which includes an OLED, a wireless receiver, and a controller configured to provide a control signal to the OLED specifying the desired light characteristic in real-time, where the control signal causes the OLED to emit light having the desired light characteristic. The signal received by each wireless receiver may be the sensor signal, or it may be another signal received from another lighting component, a central controller, or the like.
In an embodiment, the system may include a replacement lighting component, such that upon addition of the replacement lighting component, the replacement lighting component receives the signal and emits light defined by the signal in real-time. The light defined by the signal may be based upon light emitted by at least one of the lighting components.
In an embodiment, one or more lighting components may include a mechanism configured to position the lighting component to generate a visible pattern defined by the desired light characteristic.
In various embodiments, each may be flexible, partially or entirely transparent, and/or include a large-area OLED panel.
Generally, an OLED comprises at least one organic layer disposed between and electrically connected to an anode and a cathode. When a current is applied, the anode injects holes and the cathode injects electrons into the organic layer(s). The injected holes and electrons each migrate toward the oppositely charged electrode. When an electron and hole localize on the same molecule, an “exciton,” which is a localized electron-hole pair having an excited energy state, is formed. Light is emitted when the exciton relaxes via a photoemissive mechanism. In some cases, the exciton may be localized on an excimer or an exciplex. Non-radiative mechanisms, such as thermal relaxation, may also occur, but are generally considered undesirable.
The initial OLEDs used emissive molecules that emitted light from their singlet states (“fluorescence”) as disclosed, for example, in U.S. Pat. No. 4,769,292, which is incorporated by reference in its entirety. Fluorescent emission generally occurs in a time frame of less than 10 nanoseconds.
More recently, OLEDs having emissive materials that emit light from triplet states (“phosphorescence”) have been demonstrated. Baldo et al., “Highly Efficient Phosphorescent Emission from Organic Electroluminescent Devices,” Nature, vol. 395, 151-154, 1998; (“Baldo-I”) and Baldo et al., “Very high-efficiency green organic light-emitting devices based on electrophosphorescence,” Appl. Phys. Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), which are incorporated by reference in their entireties. Phosphorescence is described in more detail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporated by reference.
More examples for each of these layers are available. For example, a flexible and transparent substrate-anode combination is disclosed in U.S. Pat. No. 5,844,363, which is incorporated by reference in its entirety. An example of a p-doped hole transport layer is m-MTDATA doped with F4-TCNQ at a molar ratio of 50:1, as disclosed in U.S. Patent Application Publication No. 2003/0230980, which is incorporated by reference in its entirety. Examples of emissive and host materials are disclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which is incorporated by reference in its entirety. An example of an n-doped electron transport layer is BPhen doped with Li at a molar ratio of 1:1, as disclosed in U.S. Patent Application Publication No. 2003/0230980, which is incorporated by reference in its entirety. U.S. Pat. Nos. 5,703,436 and 5,707,745, which are incorporated by reference in their entireties, disclose examples of cathodes including compound cathodes having a thin layer of metal such as Mg:Ag with an overlying transparent, electrically-conductive, sputter-deposited ITO layer. The theory and use of blocking layers is described in more detail in U.S. Pat. No. 6,097,147 and U.S. Patent Application Publication No. 2003/0230980, which are incorporated by reference in their entireties. Examples of injection layers are provided in U.S. Patent Application Publication No. 2004/0174116, which is incorporated by reference in its entirety. A description of protective layers may be found in U.S. Patent Application Publication No. 2004/0174116, which is incorporated by reference in its entirety.
The simple layered structure illustrated in
Structures and materials not specifically described may also be used, such as OLEDs comprised of polymeric materials (PLEDs) such as disclosed in U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated by reference in its entirety. By way of further example, OLEDs having a single organic layer may be used. OLEDs may be stacked, for example as described in U.S. Pat. No. 5,707,745 to Forrest et al, which is incorporated by reference in its entirety. The OLED structure may deviate from the simple layered structure illustrated in
Unless otherwise specified, any of the layers of the various embodiments may be deposited by any suitable method. For the organic layers, preferred methods include thermal evaporation, ink-jet, such as described in U.S. Pat. Nos. 6,013,982 and 6,087,196, which are incorporated by reference in their entireties, organic vapor phase deposition (OVPD), such as described in U.S. Pat. No. 6,337,102 to Forrest et al., which is incorporated by reference in its entirety, and deposition by organic vapor jet printing (OVJP), such as described in U.S. Pat. No. 7,431,968, which is incorporated by reference in its entirety. Other suitable deposition methods include spin coating and other solution based processes. Solution based processes are preferably carried out in nitrogen or an inert atmosphere. For the other layers, preferred methods include thermal evaporation. Preferred patterning methods include deposition through a mask, cold welding such as described in U.S. Pat. Nos. 6,294,398 and 6,468,819, which are incorporated by reference in their entireties, and patterning associated with some of the deposition methods such as ink-jet and OVJP. Other methods may also be used. The materials to be deposited may be modified to make them compatible with a particular deposition method. For example, substituents such as alkyl and aryl groups, branched or unbranched, and preferably containing at least 3 carbons, may be used in small molecules to enhance their ability to undergo solution processing. Substituents having 20 carbons or more may be used, and 3-20 carbons is a preferred range. Materials with asymmetric structures may have better solution processibility than those having symmetric structures, because asymmetric materials may have a lower tendency to recrystallize. Dendrimer substituents may be used to enhance the ability of small molecules to undergo solution processing.
Devices fabricated in accordance with embodiments of the present invention may further optionally comprise a barrier layer. One purpose of the barrier layer is to protect the electrodes and organic layers from damaging exposure to harmful species in the environment including moisture, vapor and/or gases, etc. The barrier layer may be deposited over, under or next to a substrate, an electrode, or over any other parts of a device including an edge. The barrier layer may comprise a single layer, or multiple layers. The barrier layer may be formed by various known chemical vapor deposition techniques and may include compositions having a single phase as well as compositions having multiple phases. Any suitable material or combination of materials may be used for the barrier layer. The barrier layer may incorporate an inorganic or an organic compound or both. The preferred barrier layer comprises a mixture of a polymeric material and a non-polymeric material as described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos. PCT/US2007/023098 and PCT/US2009/042829, which are herein incorporated by reference in their entireties. To be considered a “mixture”, the aforesaid polymeric and non-polymeric materials comprising the barrier layer should be deposited under the same reaction conditions and/or at the same time. The weight ratio of polymeric to non-polymeric material may be in the range of 95:5 to 5:95. The polymeric material and the non-polymeric material may be created from the same precursor material. In one example, the mixture of a polymeric material and a non-polymeric material consists essentially of polymeric silicon and inorganic silicon.
Devices fabricated in accordance with embodiments of the invention may be incorporated into a wide variety of consumer products, including flat panel displays, computer monitors, medical monitors, televisions, billboards, lights for interior or exterior illumination and/or signaling, heads up displays, fully transparent displays, flexible displays, laser printers, telephones, cell phones, personal digital assistants (PDAs), laptop computers, digital cameras, camcorders, viewfinders, micro-displays, 3-D displays, vehicles, a large area wall, theater or stadium screen, or a sign. Various control mechanisms may be used to control devices fabricated in accordance with the present invention, including passive matrix and active matrix. Many of the devices are intended for use in a temperature range comfortable to humans, such as 18 degrees C. to 30 degrees C., and more preferably at room temperature (20-25 degrees C.), but could be used outside this temperature range, for example, from -40 degree C. to +80 degree C.
The materials and structures described herein may have applications in devices other than OLEDs. For example, other optoelectronic devices such as organic solar cells and organic photodetectors may employ the materials and structures. More generally, organic devices, such as organic transistors, may employ the materials and structures.
The terms halo, halogen, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, heterocyclic group, aryl, aromatic group, and heteroaryl are known to the art, and are defined in U.S. Pat. No. 7,279,704 at cols. 31-32, which are incorporated herein by reference.
Various devices are known that use a color sensor in combination with one or more LEDs to match a desired color. For example, novelty toys such as disclosed in “Huey the Color-Changing Chameleon LED Lamp,” available at http://www.vat19.com/dvds/huey-color-copying-chameleon-lamp.cfm, use a hollow translucent plastic shell containing red, blue and green LEDs with a color sensor affixed to the underside. The color of light emitted by the device matches the color of the surface on which it sits. Another device is described in “Chameleon scarf coordinates with your outfit,” available at http://www.newscientist.com/article/dn8440-chameleon-scarf-coordinates-with-your-outfit.html, which includes a scarf that automatically coordinates its color with an adjacent article of clothing by tuning an array of LEDs embedded in the fabric. Similarly, PCT application WO 2007/072352 discloses a pair of color-tunable eyeglasses with color-matching functionality. Each of these devices relies upon a color sensor to match or co-ordinate the color of an object to that of a nearby surface. However, neither appears to be used for a large-area lighting application, partly because these devices use LEDs, and partly because each color sensing unit appears to be directly connected to the LED control system.
In contrast, embodiments of the present invention enable OLEDs to work as a dynamic lighting system for general illumination. This is made possible in part by the development of a color detector that can be remotely located from and placed in wireless communication with the illumination source, thus allowing the sensor to be independent of the illumination source itself or to be used as an intuitive color input system. For example, such a detector may serve as an input to a dynamic quality lighting system, rather than simply reproducing a color that it is located on or nearby.
Some general illumination devices provide the capability for a fixture to provide light of a desired color, such as described in U.S. Patent Nos. 7,598,686, 6,776,496, and 6,787,990. Such devices generally describe individual fixtures, which lack real-time color tuning capability to affect the quality of large area illumination. They also require the use of a fixture into which an emissive device such as an OLED panel is inserted and removed as required. In contrast, embodiments of the present invention do not require a separate fixture. Some embodiments may be integrated into a luminaire and may be battery powered, inductively coupled to a remote power loop, or plugged into a power outlet. The absence of a “light bulb” analog that is removably inserted into a fixture may increase the functionality of embodiments disclosed herein. For example, OLEDs disclosed herein may be placed anywhere on a wall or a ceiling, or may be free standing within a room, being effectively divorced from the requirement of placing them in a particular location defined by a power connection.
U.S. Patent Application Pub. No. 2010/0253229 describes a remote control for an OLED which also functions as a light detector. However, the systems disclosed therein do not provide color tunability or input methods and systems as disclosed herein. U.S. Patent Application Pub. No. 2011/0187668 and WO 2010/038179 describe proximity sensors that control an array of OLEDs, such as by way of an illuminated mirror that reflects an approaching body with a responsive pattern of illumination. Such devices do not provide any means of remote input to control the color of one or more OLED luminaires. WO/2010/125496 describes an OLED that senses daylight to determine whether the OLED should be activated. The disclosed system uses the OLED itself as a photodetector, which is inefficient, and fails to provide any mechanism for color control of the OLED.
Some systems, such as the “Hue” system provided by Philips and described at http://www.meethue.com/en-US, offer options for control of color-tunable LED lighting. However, such systems require a user to select a specific desired color, for example by selecting a desired color from a smartphone palette. In contrast, the systems and techniques disclosed herein do not require specific color selection by a user, thus providing for more reliable color matching, such as when operated by a color-blind person.
Embodiments of the invention provide systems and techniques for interior lighting that allows for color selection based upon remote measurements of, for example, ambient color. For example, an interior lighting system according to an embodiment may mimic the quality of exterior light by automatically varying the interior color temperature from high (at noon) to low (at sunset). As another example, the color quality of light from multiple luminaires in a system may be managed automatically, thereby reducing color binning problems that may result in relamping and other situations.
The sensor 405 includes a broadband light source 425, a color detector 430, and a wireless transmitter 420. The broadband light source may emit light toward a surface 435. The color sensing unit 430 receives light reflected by the surface 435, and may measure various characteristics of the light such as color, temperature, intensity, pattern, and the like. The measurements may then be provided to a processor such as the main control unit 415. Based upon data received from the color sensing unit 430, the main control unit 415 may determine characteristics of light to be emitted by a luminaire that will cause the emitted light to vary depending on the ambient light received from the surface 435. For example, the main control unit 415 may compare a color measurement obtained by the color sensing unit 420 to the known color of the broadband light emitted by the emitter 425, and determine the ambient light color based upon the difference between the two. In an embodiment, the surface may be a reference surface 835 with known color, reflectance, or other properties. The broadband source 425 may be omitted in such a configuration, because the main control unit 415 may be configured to determine desired light characteristics based upon the characteristics measured by the sensing unit 430 in comparison to the known characteristics of the reference surface 835.
The sensor 405 also may include a wireless transmitter 420, which may include a Bluetooth(R), WiFi, or other suitable wireless transmitter or transceiver. The sensor 405 may use the wireless transmitter 420 to provide instructions to one or more luminaires 440 sufficient for the luminaire 440 to emit light having the characteristic determined by the main control unit 415. For example, where the system is configured to match the color of outdoor light, the sensor 405 may transmit appropriate color information to the luminaire 440 that is sufficient for the luminaire to emit light of the same color as the outdoor light, as determined by the main control unit 415.
The sensor 405 also may include a power unit 410, such as an internal battery, external power supply, or connection to an available power source such as a conventional power connector suitable for connection to a home wiring system. In some embodiments it may be preferred for the power unit 410 to be an internal power source such as a battery, to allow the sensor 405 to be placed without regard for available power connections.
The luminaire 440 may be a large-area, general illumination device, or it may be a smaller-area device, such as an accent light, intended to provide limited illumination. The luminaire 440 includes at least one RGB OLED device that may be, for example, laterally or vertically patterned so that white light of a known temperature and CRI may be generated. The OLED may include separate drivers 460 for each set of red, green, and blue subpixels 470. As will be readily understood by one of skill in the art, light having one or more desired characteristics, such as a desired color, temperature, intensity, and/or pattern may be generated by driving the subpixels 470 in a combination to produce the desired light.
The wireless receiver 450 receives the signal sent by one or more wireless transmitters 420. As previously described with respect to the transmitter 420, the receiver 450 may be a Bluetooth(R), WiFi, or any other suitable wireless receiver or transceiver. A main control unit 455 may determine driving conditions of the red, green, and blue OLED subpixels based upon the light information received by the receiver 450. For example, where the signal specifies a particular color to be emitted by the luminaire 440, the main control unit may calculate the specific driving conditions for each subpixel 470 that are necessary to achieve the specified color. In an embodiment, the luminaire 440 may compare a spectrum received from the sensor 405 via the wireless receiver 450 to one or more known reference spectra 865. The main control unit may then select the closest match to the received spectrum, and cause the luminaire to emit light based upon the identified reference spectrum 865. In some cases, multiple reference spectra may be combined to produce a desired color. The reference spectra 865 also may be generated based upon the known characteristics of the reference surface 835, to allow for more efficient processing by the main control unit 455 based upon the data received from the sensor 405.
The main control unit 450 may interface with the subpixels via separate drivers 460, so as to independently control the luminosity of the red, green, and blue OLED subpixels. For example, the drivers 460 may include one or more power controllers configured to separately drive the red, green and blue OLED subpixels. The main control unit also may interface and control a mechanism for shading, obstructing or changing the angle of the red, green and blue OLEDs to achieve one or more desired light characteristic.
In an example experimental device shown in
The systems disclosed herein may be used for a variety of applications. In an embodiment, a system such as that shown in
As another example, the system may be used when re-lamping a room or area. With current lighting technology, it is often necessary to re-lamp an entire room when a single lamp fails because the color temperature of a replacement lamp differs from that of the legacy installation, which may create dissonance in the lighting profile of the room. Using the system shown in
Systems as disclosed herein also may be used to provide dynamic control of lighting quality. In an embodiment, the OLED luminaire may be mounted on a wall or ceiling. As previously disclosed, the luminaire may be battery powered or powered by a main electrical source. A color sensing unit may be wall-mounted in a convenient location such as near a door. Colored cards or objects may be presented to the color sensing unit, for example to provide the surface 435 shown in
In a similar configuration, systems as disclosed herein may be used to provide daylight mimetic dynamic artificial lighting. In an embodiment, a sensor such as the sensor 405 in
As previously described, various wireless communication systems such as Bluetooth may be used to permit the sensor to control multiple luminaires in one or more rooms. This may provide for a henceforth unobtainable degree of lighting consistency in both space and time.
In an embodiment, individual OLED lamps may be designed to integrate together into a luminaire, with the MCU of each luminaire capable of controlling multiple OLED lamps. For example, in the demonstration device, three individual OLED lamps are coupled to a diffuser to make one luminaire as shown in
Generally, OLED panels used in devices and systems disclosed herein may have any of the properties described herein and known in the art as being achievable for individual OLED panels. For example, luminaires disclosed herein may use transparent and/or flexible OLED, and may themselves be substantially or entirely transparent and/or flexible.
The light characteristics that may be measured and reproduced by systems disclosed herein may include color, texture, temperature, pattern, or other physical parameters. For example, a luminaire may receive data from one or more sensors that allows it to provide light that matches a desired color and temperature of another luminaire or of an outdoor region. As another example, an array of lamps on a ceiling may be configured into a checkerboard pattern by presenting such a pattern to the detector. As another example, the angular output of a luminaire may be changed by presenting various shades of color or physical shapes to the sensor, thus causing a physical motion of the luminaire panels or reflectors integrated into the luminaire.
It may be noted that driving an OLED as disclosed herein may be done using techniques different from driving other devices such as conventional LEDs. For example, it may be desirable for the control unit to have special functions to address unique properties of OLED devices. For example, the IVL (current-voltage-luminance) performance of an OLED may be quite different from other sources such as conventional LEDs. Even among different OLEDs, individual red, green, and blue devices may be quite different in their IVL performance. Thus, it may be desirable for the control unit to be configured to account for the IVL performance of individual RGB OLEDs into consideration. In other configurations, a sensor may be used as disclosed herein to allow the control unit to adjust the output of an OLED to achieve a desired color, thus inherently accounting for any difference in performance.
As another example, it is known that RGB OLEDs age at different speed. Thus, it may be desirable that the control unit is configured to account for different aging of individual colors.
It is understood that the various embodiments described herein are by way of example only, and are not intended to limit the scope of the invention. For example, many of the materials and structures described herein may be substituted with other materials and structures without deviating from the spirit of the invention. The present invention as claimed may therefore include variations from the particular examples and preferred embodiments described herein, as will be apparent to one of skill in the art. It is understood that various theories as to why the invention works are not intended to be limiting.
This application claims priority to U.S. Provisional Patent Application No. 61/825,214, filed May 20, 2013, the disclosure of which is incorporated by reference in its entirety. The claimed invention was made by, on behalf of, and/or in connection with one or more of the following parties to a joint university corporation research agreement: Regents of the University of Michigan, Princeton University, The University of Southern California, and the Universal Display Corporation. The agreement was in effect on and before the date the claimed invention was made, and the claimed invention was made as a result of activities undertaken within the scope of the agreement.
| Number | Date | Country | |
|---|---|---|---|
| 61825214 | May 2013 | US |
