WO2015031752A2 - Light-emitting devices - Google Patents

Abstract

Light-emitting devices are described herein.

Description

LIGHT-EMITTING DEVICES

CROSS-REFERENCE TO RELATED APPLICATIONS

[001] This application claims the benefit to Provisional Patent Application No. 61/871 ,750, filed August 29, 2013, which is incorporated herein by reference in its entirety.

BACKGROUND

[002] Organic light-emitting devices (OLED) are becoming increasingly important in lighting and display applications. However there are still significant improvements that could be made for OLED technology that may encourage widespread use. For example, to replace a conventional light source with an OLED device, it is may be helpful to raise power efficiency of OLED to a level that may compete with the level of conventional light sources. Generally, power efficiency is about 60 - 90 Im/W for fluorescent lamps. Therefore, it may be desirable to attain an efficiency of about 60 Im/W for consideration of white OLED as replacements for fluorescent lamps. The United States Department of Energy (DOE) described a 2015 target benchmark of about 150 Im/W (assuming CRI>80 and CCT = 2700-3000K). Thus there is a need to further improve device efficiency.

SUMMARY

[003] Incorporation of plural emissive layers into an OLED device may help to improve device efficiency while concurrently improving CRI values of a device.

[004] Some embodiments include a top emitting OLED device comprising: an anode; a cathode; and an emissive construct disposed between the anode and cathode; wherein the emissive construct comprises: a first blue emissive layer; wherein the first blue emissive layer is phosphorescent or fluorescent; a red emissive layer contacting the first blue emissive layer; wherein the red emissive layer is phosphorescent; and a yellow emissive layer contacting the red emissive layer; or a green emissive layer contacting the red emissive layer, and a yellow emissive layer contacting the green emissive layer; wherein the yellow emissive layer is phosphorescent and the green emissive layer, if present, is phosphorescent. [005] Some embodiments include an OLED device comprising: an anode; a cathode; and an emissive construct disposed between the anode and cathode; wherein the emissive construct comprises: a phosphorescent emissive layer that is singly doped and has a peak emissive wavelength between about 500 to about 800 nm; and a first fluorescent emissive layer, having a peak emissive wavelength between about 400 to about 500 nm.

[006] Some embodiments include an OLED device comprising: an anode; a cathode; and an emissive construct disposed between the anode and cathode; wherein the emissive construct comprises: a first blue emissive layer; wherein the first blue emissive layer is phosphorescent or fluorescent; a red emissive layer contacting the first blue emissive layer; wherein the red emissive layer is phosphorescent; a green emissive layer contacting the red emissive layer; and wherein the green emissive layer is phosphorescent.

[007] Some embodiments include an OLED device comprising: an anode; a cathode; and an emissive construct disposed between the anode and cathode; wherein the emissive construct comprises; a first blue emissive layer; wherein the first blue emissive layer is phosphorescent or fluorescent; an orange emissive layer contacting the first blue emissive layer; and wherein the orange emissive layer is phosphorescent.

[008] Some embodiments include a light-emitting device comprising an anode, a cathode, an emissive construct disposed between the anode and the cathode, and a multi- wavelength resonant layer, wherein the multi-wavelength resonance layer comprises a material having a thickness sufficient to match the resonant wavelength of the peak emission from the emissive construct, and the multi-wavelength resonant layer is disposed on the side of the cathode opposite the emissive construct.

[009] These and other embodiments are described in more detail herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[010] FIG. 1 shows a schematic depiction of an embodiment described herein.

[011] FIG. 2 is a schematic of an all phosphor emissive layered embodiment.

[012] FIGS. 3A-I shows the schematics for several embodiments of an emissive construct.

[013] FIG. 4 shows the setup to measure the electroluminescent of the top-emission WOLED device measured at 0° viewing angle. [014] FIG. 5 shows the EL spectrum of one embodiment of the device.

[015] FIG. 6 shows the brightness dependence of the device power efficiency with and without macro outcoupling lens.

[016] FIG. 7 shows the brightness dependence of the device power external quantum efficiency with and without macro outcoupling lens.

[017] FIG. 8 is a schematic depiction of an embodiment of an organic light-emitting device.

[018] FIG. 9 is a schematic depiction of an embodiment of an organic light-emitting device.

[019] FIG. 10 is a plot of the EL spectrum of the Device A2 CRI(75), CIE(0.47, 0.44).

[020] FIG. 1 1 is a plot of luminous efficiency and power efficiency against brightness (B) for Device A2.

[021] FIG. 12 is a plot of brightness over time for Device B2.

[022] FIG. 13 is a plot of luminous efficiency and power efficiency against brightness (B) for Device B2.

[023] FIG. 14 is a plot of the EL spectrum of the Device A3 (3.0 nm green layer) CRI(64), CIE(0.48, 0.45)

[024] FIG. 15 is a plot of the EL spectrum of the Device A4 (2.5 nm green layer)] CRI(55), CIE(0.56, 0.45).

[025] FIG. 16(a)-(h) are embodiments of single dopant emissive layered embodiments.

[026] FIG. 17 is a schematic of a single dopant emissive layered device embodiment of transparent WOLED.

[027] FIG. 18 is a plot of the EL spectrum of the device (device area 8 mm²) at various driving currents.

[028] FIG. 19 is a schematic of another single dopant emissive layered device embodiment. [029] FIG. 20 are plots of EL spectrum of the TE-WOLED device at 0° viewing angle and various driving currents.

[030] FIG. 21 is a schematic of another single dopant emissive layered device embodiment.

[031] FIG. 22 shows the EL spectrum of the invented TE-WOLED at 0° viewing angle and various driving currents.

[032] FIG. 23 is a schematic of a 3 color fluorescent blue emissive layered embodiment.

[033] FIGs. 24-29 are plots of EL intensity and wavelength for varying NPB layered embodiments, at 0° and 70° viewing angle.

[034] FIG. 30 is a plot of EL spectrum of the TE-WOLED device at 0° and 70 ⁰ viewing angle.

DETAILED DESCRIPTION

[035] FIG. 1 is a depiction of some embodiments of the layers of an OLED device of an embodiment comprising: a cathode 30, an anode 10, and an emissive construct 20 disposed between the cathode 30 and the anode 10. In some embodiments, the emissive construct 20 comprises an emissive layer. In some embodiments, the emissive construct may comprise a plurality of emissive layers. In some embodiments, the emissive construct may comprise a plurality of phosphorescent emissive layers. In some embodiments, the emissive construct may comprise at least one phosphorescent emissive layer and at least one fluorescent emissive layer.

[036] FIG. 2 is a schematic depiction of one embodiment. In some embodiments, the device can comprise a substrate 200, an anode 30, a hole injection layer 40, a hole transport layer 60, an emissive construct 20, an electron transport layer (ETL) 80, an electron injection layer (EIL) 90, a cathode 30, and a capping layer 100. The capping layer can comprise an emission enhancing element, a light-scattering element, and/or a resonant layer. In some embodiments, the anode may be opaque and/or reflective. In some embodiments, the cathode may be semi-transparent or transparent. In some embodiments, an insulating layer may be disposed between the substrate and the anode.

[037] In some embodiments, a light emitting device may comprise an emissive construct. In some embodiments, the emissive construct may further comprise at least one fluorescent emissive layer and at least one phosphorescent emissive layer. In some embodiments, the emissive construct may comprise more than one fluorescent emissive layer. In some embodiments, the emissive construct may comprise more than one phosphorescent emissive layer.

[038] Unless otherwise indicated, any emissive layer for any device described herein can be singly doped. An emissive layer structure with only one dopant can make a fabrication process simpler and/or easier. The term singly doped refers to a layer with substantially only one dopant. The emissive layers can comprise of phosphorescent emissive layers and fluorescent emissive layers. Non-limiting examples of devices comprising singly doped emissive layers are provided in FIGS, 16, 17, 19, 21 and 23.

[039] Some embodiments include emissive constructs comprising a fluorescent layer and one or more phosphorescent layers. In such an embodiment, the fluorescent emissive layer can emit blue light covering the wavelength range from 400-500 nm. In some embodiments, phosphorescent emissive layers can emit light covering spectrum range from 500 nm to 800 nm. In some embodiments, phosphorescent emissive layers can emit light covering spectrum range from 400 nm to 800 nm. In some embodiments, the mixture of the emitted light provides white-color by the top-emission devices.

[040] In some embodiments, each layer emits light covering a certain wavelength range. In some embodiments, the combined emission of the emissive layers covers the entire 500-800 nm range. In some embodiments, the combined emission of the emissive layers covers the entire 350-800 nm range. In some embodiments, the phosphorescent layers may emit different colors.

[041] In some embodiments, a white light emissive construct is provided comprising a singly doped phosphorescent emissive layer having a peak emissive wavelength between about 500 to about 800 nm, and a fluorescent blue emissive layer, having a peak emissive wavelength between about 400 to about 500 nm.

[042] In some embodiments, the phosphorescent emissive layer and the fluorescent emissive layer define an exciton regeneration zone. In some embodiments, the exciton regeneration zone can have a thickness in the range of between about 1 nm to about 60 nm. In some embodiments, the exciton regeneration zone can be about 1 nm thick, about 2 nm thick, about 3 nm thick, about 4 nm thick, about 5 nm thick, about 10 nm thick, about 20 nm thick, about 30 nm thick, about 40 nm thick, about 50 nm thick, about 60 nm thick. In some embodiments, the exciton regeneration zone can have a thickness in any combination of the aforementioned ranges, up to about 60 nm thick. In some embodiments, the exciton regeneration zone may be about 10 nm thick. In some embodiments, the total thickness of the phosphorescent emissive layer may be less than the thickness of the exciton regeneration zone. In some embodiments the total thickness of the phosphorescent emissive layer can be less than about 10 nm.

[043] In another embodiment, the fluorescent emissive layer has a thickness range from between about 5 nm, about 10 nm to about 20 nm, to about 25 nm, to about 30 nm, to about 40 nm, to about 50 nm and/or any permutations of the above described ranges. In another embodiment, the fluorescent emissive layer has a thickness of about 15 nm.

[044] In some embodiments, the fluorescent emissive layer comprises a neat fluorescent blue emitter layer. In some embodiments, the fluorescent emissive layer comprises a blue fluorescent emitter. In some embodiments, the fluorescent emissive layer comprises a fluorescent host and a single blue emitter. In some embodiments, the T1 of the fluorescent host material and the fluorescent blue emitter in the fluorescent emissive layer is higher than the T1 of the phosphorescent emitters in the phosphorescent emissive layer.

[045] In some embodiments, the white light emitting construct may comprise a hole blocking layer, wherein the phosphorescent emissive layer may be disposed between the fluorescent blue emissive layer and the hole blocking layer. In some embodiments, the fluorescent emissive layer and the phosphorescent emissive layer comprise the same host material.

[046] In some embodiments, the light emitting device can comprise a capping layer 100. In some embodiments, the capping layer can be a resonant layer. In some embodiments, the resonant layer can be multi-wavelength. In some embodiments, the light emitting device comprises a microcavity defined by a bottom reflective electrode and a top semi-transparent electrode. In some embodiment, the capping layer 100 comprises a multi- wavelength-resonant layer disposed over the top semi-transparent electrode.

[047] In some embodiments, the emissive construct may comprise a plurality of phosphorescent and/or fluorescent emissive layers. In some embodiments, the combined emission of the emissive layers renders white light. The term "white light" refers to light that appears white and is created by blending different colors of light to produce the appearance of white. One known combination includes red, green, and blue light. Another known combination includes cyan, magenta, and yellow light. Those skilled in the art will recognize color combinations that create white light. In some embodiments, the emissive construct may comprise a blue emissive layer. In some embodiments, the emissive construct comprises a red emissive layer. In some embodiments, the emissive construct comprises a phosphorescent yellow emissive layer. In some embodiments, the emissive construct comprises a phosphorescent green layer.

[048] In some embodiments, such as that depicted in FIG. 3A, an emissive construct, e.g. emissive construct 20, comprises, a blue emissive layer 2, a red emissive layer 4 contacting the blue emissive layer, and a yellow emissive layer 6 contacting the red emissive layer 4. In some embodiments, the red emissive layer 4 is disposed atop and contacting said blue emissive layer 2. In some embodiments, the yellow emissive layer 6 is disposed atop and contacting said red emissive layer 4. In some embodiments, the above described layers are so disposed in order from bottom to top.

[049] In some embodiments, such as that depicted in FIG. 3B, an emissive construct, e.g. emissive construct 20, comprises, a first blue emissive layer 2, a red emissive layer 4 contacting the blue emissive layer, a yellow emissive layer 6 contacting the red emissive layer 4, and a second blue emissive layer 8 contacting the yellow emissive layer 6. In some embodiments, the red emissive layer 4 is disposed atop and contacting said first blue emissive layer 2. In some embodiments, the yellow emissive layer 6 is disposed atop and contacting said red emissive layer 4. In some embodiments, the second blue emissive layer 8 is disposed atop and contacting said yellow emissive layer 6. In some embodiments, the above described layers are so disposed in order from bottom to top.

[050] In some embodiments, such as that depicted in FIG. 3C, an emissive construct, e.g. emissive construct 20, comprises, a first blue emissive layer 2, a red emissive layer 4 contacting the first blue emissive layer 2, and a green emissive layer 7 contacting the red emissive layer 4, and a second blue emissive layer 8 contacting the green emissive layer 7. In some embodiments, the red emissive layer 4 is disposed atop and contacting said first blue emissive layer 2. In some embodiments, the green emissive layer 7 is disposed atop and contacting said red emissive layer 4. In some embodiments, the second blue emissive layer 8 is disposed atop and contacting said green emissive layer 7. In some embodiments, the above described layers are so disposed in order from bottom to top.

[051] In some embodiments, such as that depicted in FIG. 3D, an emissive construct, e.g. emissive construct 20, comprises a first blue emissive layer 2, a red emissive layer 4 contacting the first blue emissive layer 2, and a green emissive layer 7 contacting the red emissive layer 4, and a yellow emissive layer 6 contacting the green emissive layer 7. In some embodiments, the red emissive layer 4 is disposed atop and contacting said first blue emissive layer 2. In some embodiments, the green emissive layer 7 is disposed atop and contacting said red emissive layer 4. In some embodiments, the yellow emissive layer 6 is disposed atop and contacting said green emissive layer 7. In some embodiments, the above described layers are so disposed in order from bottom to top.

[052] In some embodiments, such as that depicted in FIG. 3E, an emissive construct, e.g. emissive construct 20, comprises a first blue emissive layer 2, a red emissive layer 4 contacting the first blue emissive layer 2, and a green emissive layer 7 contacting the red emissive layer 4, and a yellow emissive layer 6 contacting the green emissive layer 7, and a second blue emissive layer 8 contacting the yellow emissive layer 6. In some embodiments, the red emissive layer 4 is disposed atop and contacting said first blue emissive layer 2. In some embodiments, the green emissive layer 7 is disposed atop and contacting said red emissive layer 4. In some embodiments, the yellow emissive layer 6 is disposed atop and contacting said green emissive layer 7. In some embodiments, the second blue emissive layer 8 is disposed atop and contacting said yellow emissive layer 6. In some embodiments, the above described layers are so disposed in order from bottom to top.

[053] In some embodiments, such as that depicted in FIG. 3F, an emissive construct, e.g. emissive construct 20, comprises a first blue emissive layer 2, a red emissive layer 4 contacting the first blue emissive layer 2, and a green emissive layer 7 contacting the red emissive layer 4. In some embodiments, the red emissive layer 4 is disposed atop and contacting said first blue emissive layer 2. In some embodiments, the green emissive layer 7 is disposed atop and contacting said red emissive layer 4. In some embodiments, the above described layers are so disposed in order from bottom to top. [054] In some embodiments, such as that depicted in FIG. 3G, an emissive construct, e.g. emissive construct 20, comprises a first blue emissive layer 2, a red emissive layer 4 contacting the first blue emissive layer 2, and a yellow emissive layer 6 contacting the red emissive layer 4. In some embodiments, the red emissive layer 4 is disposed atop and contacting said first blue emissive layer 2. In some embodiments, the yellow emissive layer 6 is disposed atop and contacting said red emissive layer 4. In some embodiments, the above described layers are so disposed in order from bottom to top.

[055] In some embodiments, such as that depicted in FIG. 3H, an emissive construct, e.g. emissive construct 20, comprises a first blue emissive layer 2, an orange emissive layer 11 contacting the first blue emissive layer 2, and a second blue emissive layer 8 contacting the orange emissive layer 11. In some embodiments, the orange emissive layer 11 is disposed atop and contacting said first blue emissive layer 2. In some embodiments, the second blue emissive layer 8 is disposed atop and contacting said orange emissive layer 11 . In some embodiments, the above described layers are so disposed in order from bottom to top.

[056] In some embodiments, such as that depicted in FIG. 3I, an emissive construct, e.g. emissive construct 20, comprises a first blue emissive layer 2 and an orange emissive layer 11 contacting the first blue emissive layer 2. In some embodiments, the orange emissive layer 11 is disposed atop and contacting said first blue emissive layer 2. In some embodiments, the above described layers are so disposed in order from bottom to top.

[057] For any embodiment herein, such as those comprising an emissive construct illustrated by FIGS. 3A-I, the first blue emissive layer, e.g. first blue emissive layer 2, can be between the anode and the red emissive layer 4 or the orange emissive layer 11. Alternatively, first blue emissive layer, e.g. first blue emissive layer 2, can be between the cathode and the red emissive layer 4 or the orange emissive layer 11.

[058] The total thickness of the emissive layers can be in the range of about 0.1 nm to about 200 nm, up to about 50 nm thick, about 0.1 nm thick, about 0.2 nm thick, about 0.3 nm thick, about 0.4 nm thick, about 0.5 nm thick, about 1 .0 nm thick, about 2.0 nm thick, about 3.0 nm thick, about 4.0 nm thick, about 5.0 nm thick, about 10 nm thick, about 20 nm thick, about 30 nm thick, about 40 nm thick, about 50 nm thick, or about 100 nm thick, or any thickness bounded by or between and of these values. [059] FIG. 8 is a schematic representation of the structure of some embodiments of the emissive construct 20 between a first electrode such as anode 10 and a second electrode, such as cathode 30. In some embodiments, the first electrode, anode 10 may be a reflective anode disposed on substrate 200. Optionally, a hole-injection layer 40 may be disposed on anode 10. Optionally, a p-doped hole-transport layer 50 may be disposed on hole-injection layer 40. Optionally, a hole-transport layer 60 may be disposed on p-doped hole-transport layer 50. Optionally, the emissive construct 20 may be disposed on hole- transport layer 60. Optionally, an electron transport layer 80 may be disposed on emissive construct 10 (phosphorescent emissive layer 18). Optionally, an electron injection layer 90 may be disposed on electron transport layer 80. Optionally, the cathode 30 may be disposed on electron injection layer 90 Optionally, a capping layer 100 may be disposed on cathode 30. . Optionally, a light-scattering layer 130 may be disposed on top of the capping layer 100. In some embodiments, cathode 30 is a semi-transparent cathode. In one embodiment, the light-scattering layer 130 may be plural nanostructures described in any of the following documents: U.S. Patent Publication No. 2012/0223635 (Ser. No. 13/410,812, filed March 2, 2012, U.S. Patent Application Ser. No. 13/672,394, filed November 8, 2012 and U.S. Provisional Application Ser. No. 61/696,085, filed August 31 , 2012, which is incorporated by reference for their description of appropriate nanostructured materials and outcoupling materials.

[060] For an emissive layer of any color in the visible range, such as blue, red, orange, green, yellow, etc., any suitable host material may be used. In some embodiments, a host may be an ambipolar compound or material. In some embodiments, a host material may be fluorescent or phosphorescent in the near UV or blue range.

[061] In some embodiments, a host material for any emissive layer may have a high T1 , such as at least about 2.15 eV, at least about 2.20 eV, at least about 2.25 eV, at least about 2.3 eV, at least about 2.35 eV, at least about 2.36 eV, at least about 2.37 eV, at least about 2.4 eV, at least about 2.7 eV, at least about 2.65 eV, at least about 2.70 eV, at least about 2.75 eV, and/or at least about 2.78 eV.

[062] Suitable hosts include, but are not limited to those described in co-pending applications United States Patent Publication No. 201 1/0140093 (Ser. No. 13/033,473, filed February 23, 201 1 ; United States Patent Publication No. 201 1/0251401 (Ser. No. 13/166,246, filed June 1 1 , 201 1 , United States Provisional Application No. 61/735,478, filed on 10-Dec-2012); United States Patent Publication 2007/0088167, published April 19, 2007; United States Patent Publication US 201 1/0057559, published March 10, 201 1 ; United States Patent 8,062,772, issued November 22, 201 1 ; co-pending United States Provisional Application 61/835,393, filed June 14, 2013; United States Patent Application Ser. No. 12/883,018, filed 15-Sep-2012 (US Publication 201 1 /0062386, published March 17, 201 1 ), U.S. Patent Publication No. 2010/0326526 (Ser. No. 12/825,953, filed June 29, 2010); United States Patent No,. 8,426,040, issued April 23, 2013 and United States Patent Application; all of which are incorporated by reference in their entireties. In some embodiments, the host compound may be:

Table 1

2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (DCzDBT) 2.85

[063] The emissive layer or layers described herein may comprise a dopant material in an amount of about 1 % to about 50% by volume of the emissive layer. In some embodiments, the dopant material can comprise about 0.1 % to about 10%, about 1 % to about 5%, about 1 %, about 2%, about 3% about 4%, about 5%, about 10%, about 20%, about 30%, about 40%, about 50% by volume of the emissive layer. In some embodiments, the dopant material can comprise any combination of the aforementioned percentages, up to about 50% by volume of the emissive layer. [064] Any suitable amount of host can be used in a light-emitting layer. In some embodiments, the amount of a host in a light-emitting layer is in the range of from about 70% to nearly 100% by volume of the light-emitting layer, such as about 90% to about 99%, or about 97% by volume of the light-emitting layer.

[065] In some embodiments, an emissive layer may have a thickness in the range of up to about 50 nm, about 5 nm to about 50 nm, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, about 10 nm, about 15 nm, about 20 nm, about 25 nm, about 30 nm, about 40 nm, about 50 nm, or any thickness in a range bounded by, or between, any of these values.

[066] A blue emissive layer, such as a first blue emissive layer (e.g. first blue emissive layer 2 in FIGS. 3A-I) or a second blue emissive layer (e.g. second blue emissive layer 8 in FIGS. 3B, 3C, 3E, OR 3H) can be phosphorescent or fluorescent.

[067] A fluorescent blue emissive layer can comprise a neat fluorescent layer, or can comprise a host material and a fluorescent dopant. Similarly, a phosphorescent layer can comprise a neat phosphorescent layer, or can comprise a host material and a phosphorescent dopant.

[068] In some embodiments, the blue emissive layer may comprise a host material and a dopant material. In some other embodiments, the host may be a compound having a T1 value (e.g. energy of the lowest energy triplet) higher than the T1 value of the emissive component (e.g. the T1 of the dopant or the T1 of a compound composing a neat layer) of the red emissive layer (e.g. red emissive layer 4 of FIGS. 3A-G), the emissive component of the orange emissive layer (e.g. orange emissive layer 1 1 of FIGS. 3H-I), or any other phosphorescent layer that emits light having a wavelength longer than blue light. In some embodiments, the host material may have a high T1 , such as at least about 2.15 eV, at least about 2.20 eV, at least about 2.25 eV, at least about 2.3 eV, at least about 2.35 eV, at least about 2.36 eV, at least about 2.37 eV, at least about 2.4 eV, at least about 2.7 eV, at least about 2.65 eV, at least about 2.70 eV, at least about 2.75 eV, and/or at least about 2.78 eV.

[069] In some embodiments, the host can be optionally substituted DCzDBT, optionally substituted Host-3, optionally substituted Host-1 , or optionally substituted Host-8. In some embodiments, the host can be DCzDBT, Host-3, Host-1 , or Host-8. In some embodiments, the host may comprise DCzDBT. In some embodiments, the host may comprise Host-1 .

[070] A dopant for a blue emissive layer may be a dopant with blue light fluorescence or phosphorescence. Suitable compounds that may be useful as fluorescent blue dopant materials may include, but are not limited to, any compound described in one of the following documents: United States Application No. 13/971 ,081 , filed August 20, 2013, which is incorporated by reference for all disclosure related to new compounds; United States Patent Application No.13/232,837, filed September 14, 201 1 , and published as US 20120179089, which is incorporated by reference for all disclosure related to new compounds; and United States Provisional Application No. 61/735,488, filed December 10, 2012, which is incorporated by reference for all disclosure related to new compounds. In some other embodiments, a fluorescent blue dopant may be any of:

N,N-diphenyl-4-(6'-(1 -phenyl-1 H-benzo[d]imidazol-2-yl)-[3,3'-bipyridin]-6-yl)aniline

(BE-1 )

4'-(6-(1 -phenyl-1 H-benzo[d]imidazol-2-yl)pyridin-3-yl)-N,N-di-p-tolyl-[1 ,1 '-biphenyl]-4- amine (BE-2),

N-phenyl-N-(4-(5-(4-(1 -phenyl-1 H-benzo[d]imidazol-2-yl)phenyl)pyrazin-2- yl)phenyl)naphthalen-1 -amine (BE-3), and

4^,,-(1 henyl-1H-benzo[d]imidazol-2-yl)-N,N-di-p olyl-[1,1^4 1 eφhenyl]-4-amine

N,N-diphenyl-4"-(1-phenyl-1H-benzo[d]imidazol-2-yl)-[1,1^4\1"-terphenyl]-4-ami

(BE-5)

N,N-diphenyl-4^,, 1-phenyl-1H-benzo[d]imidazol-2-yl)-[1,1^4 1^,^4 1^,,,-quaterphenyl]- 4-amine (BE-6)

[071] In some embodiments, a blue emissive layer comprises BE-3 as a fluorescent dopant.

[072] Phosphorescent blue dopants can also include, but are not limited to:

bis-{2-[3,5-bis(trifluoromethyl)phenyl]pyridinato-N,C2'}iridium(lll)-picolinate

(lr(CF₃ppy)₂(Pic) [PBE-1],

bis(2-[4,6-difluorophenyl]pyridinato-N,C2')iridium (III) picolinate [FIrPic] [PBE-2],

bis(2-[4,6-difluorophenyl]pyridinato-N,C2')iridium(acetylacetonate) [Flr(acac)] [PBE-],

Iridium (III) bis(4,6-difluorophenylpyridinato)-3-(trifluorornethyl)-5-(pyridine-2-yl)- ,2,4-triazolate (FIrtaz) [PBE-4] ,

Iridium (III) bis(4,6-difluorophenylpyridinato)-5-(pyridine-2-yl)-1 H-tetrazolate (FlrN4) [PBE-5],

bis[2-(4,6-difuluorophenyl)pyridinato-N,C²]iridium(ll l)tetra(1 -pyrazolyl)borate (Fir6) [PBE-6],

PBE-7.

[073] In some embodiments, the dopant in a blue emissive layer can be PBE-7.

[074] For emissive layers comprising a dopant and a host, such as a blue emissive layer (e.g. a first blue emissive layer or a second blue emissive layer), any suitable dopant concentration may be used. For example, the dopant concentration in a blue emissive layer can be about 0.01 % to 50%, about 0.01 % to 10%, about 2.0% to 15%, about 5% to about 20%, about 4% to about 8%, about 12%, about 5%, about 7%, or about 6% dopant by weight or volume, or any amount of dopant in a range bounded by, or between, any of these values.

[075] In some embodiments, the blue emissive layer comprises about 5% by weight of BE-1 , BE-2, or BE-3.

[076] An emissive layer, such as a blue emissive layer, may have any suitable thickness. In some embodiments, an emissive layer, such as the first blue emissive layer or the second blue emissive layer, may have a thickness up to about 50 nm, about 5 nm to about 50 nm, about 5 nm to about 20 nm, about 5 nm to about 15 nm, about 10 nm, about 12 nm, about 15 nm, about 20 nm, or any thickness in a range bounded by, or between, any of these values.

[077] In some embodiments, a blue emissive layer comprises BE-3 as a dopant and Host-1 as a host. In some embodiments, a blue emissive layer comprises BE-5 as a dopant and Host-1 as a host. In some embodiments, a blue emissive layer comprises PBE- 7 as a dopant and DCzDBT as a host.

[078] In some embodiments, the second blue emissive layer comprises BE-5 as a dopant and Host-1 as a host.

[079] A red emissive layer, such as red emissive layer 2 in FIGS. 3A-G, can be phosphorescent or fluorescent. In some embodiments, a red emissive layer can be phosphorescent. A phosphorescent layer can comprise a neat phosphorescent layer, or can comprise a host material and a phosphorescent dopant.

[080] A host material used in a red emissive layer can be any host described above. In some embodiments, the host can be optionally substituted DCzDBT, optionally substituted Host-3, optionally substituted Host-1 , or optionally substituted Host-8. In some embodiments, the host can be DCzDBT, Host-3, Host-1 , or Host-8. In some embodiments, the host may comprise DCzDBT. In some embodiments, the host may comprise optionally substituted Host-1 . In some embodiments, the host may comprise Host-1 . [081] Any suitable material that emits red light by fluorescence or phosphorescence may be used as a red emissive material, such as a neat red emissive layer or a red emitting dopant. In some embodiments, the red emissive material or dopant is:

1 . (Btp)₂lr(lll)(acac); bis[2-(2'-benzothienyl)-pyridinato-N,C3'] iridium (lll)(acetylacetonate)

2. (Pq)₂lr(ll l)(acac); bis[(2-phenylquinolyl)-N,C2']iridium (III) (acetylacetonate)

3. (Piq)₂lr(lll)(acac); bis[(1 -phenylisoquinolinato-N,C2')]iridium (I II) (acetylacetonate)

4. (DBQ)₂lr(acac); bis[(dibenzo[f, h]quinoxalino-N,C2')iridium (lll)(acetylacetonate)

5. [lr(HFP)₃], tris(2,5-bis-2'-(9',9'-dihexylfluorene)pyridine)iridium (III)

6. lr(piq)_3; ths[1 -phenylisoquinolinato-N,C2']iridium (III)

7. lr(btp)3; tris-[2-(2'-benzothienyl)-pyridinato-N,C3'] iridium (III)

8. Ir(tiq)3, tris[1 -thiophen-2-ylisoquinolinato-N,C3']iridium (III)

9. Ir(fliq)₃; tris[1 -(9,9-dimethyl-9H-fluoren-2-yl)isoquinolinato-(N,C3')iridium (III)). In some embodiments, the red dopant material may comprise lr(piq)₂acac. [082] For red emitting layers comprising a host and a dopant, any suitable amount of dopant may be used. In some embodiments, the red dopant material may be up to about 50%, about 2% and about 20%, about 5% and about 20%, about 5% to about 10%, about 5%, about 10%, or about 12% dopant by weight or volume, or any amount of dopant in a range bounded by, or between, any of these values.

[083] In some embodiments the red emissive layer is doped with about 10% lr(piq)₂acac by weight or volume. In some embodiments the red emissive layer is doped with about 5% lr(piq)₂acac by weight or volume.

[084] A red emissive layer may have any suitable thickness. In some embodiments, the red emissive layer has a thickness of about 0.1 nm to about 20 nm, about 0.1 nm to about 10 nm, about 1 nm, or any thickness in a range bounded by, or between, any of these values.

[085] In some embodiments, a red emissive layer is about 1 nm thick and has 10% doping of lr(piq)₂acac by weight or volume in Host-1 . In some embodiments, a red emissive layer is about 1 nm thick and has 5% doping of lr(piq)₂acac by weight or volume in Host-1 .

[086] A yellow emissive layer, such as yellow emissive layer 6 in FIGS. 3A, 3B, 3D, 3E, and 3G, can be phosphorescent or fluorescent. In some embodiments, a yellow emissive layer can be phosphorescent. A phosphorescent layer can comprise a neat phosphorescent layer, or can comprise a host material and a phosphorescent dopant.

[087] A host material used in a yellow emissive layer can be any host described above. In some embodiments, the host can be optionally substituted DCzDBT, optionally substituted Host-3, optionally substituted Host-1 , or optionally substituted Host-8. In some embodiments, the host can be DCzDBT, Host-3, Host-1 , or Host-8. In some embodiments, the host of a yellow emissive layer may comprise optionally substituted Host-1 .

[088] In some embodiments, the red emissive layer and the yellow emissive layer have the same host.

[089] Any suitable material that emits yellow light by fluorescence or phosphorescence may be used as a yellow emissive material, such as a neat yellow emissive layer or a yellow emitting dopant. In some embodiments, the yellow emissive material or dopant is a compound shown below.

(bt)₂lr(lll)(acac) (f-bt)₂lr(lll)(acac) (thp)₂lr(lll)(acac) bis[2- bis[2-(4-tert-butylphenyl) bis[(2-(2'-thienyl) phenylbenzothiazola benzothiazolato-N,C2']irid pyridinato- to -N,C2'] iridium (III) (acetylacetonate) N,C3')]iridium

(acetylacetonate) (acetylacetonate)

[lr(Flpy)₃] (Cz-CF₃)lr(lll)(acac) (2-PhPyCz)₂ lr(lll)(acac) tris[2-(9.9- Bis[5-trifluoromethyl-2-[3-(N- dimethylfluoren-2-yl) phenylcarbzolyl) pyridinato- pyridinato- N,C2']iridium(lll)

(N,C3')]iridium (III) (acetylacetonate)

[090] In some embodiments, the yellow emissive layer dopant may comprise YE-

01 .

[091] For yellow emitting layers comprising a host and a dopant, any suitable amount of dopant may be used. In some embodiments, the yellow emissive layer may comprise about 5 to about 20%, up to about 10%, about 2% to about 10%, about 5%, about 6 wt% dopant by weight or volume, or any amount of dopant in a range bounded by, or between, any of these values.

[092] A yellow emissive layer may have any suitable thickness. In some embodiments, the yellow emissive layer may have a thickness up to about 50 nm, about 2 nm to about 50 nm, about 5 nm to about 50 nm, about 4 nm to about 30 nm, about 4 nm, about 20 nm, about 30 nm, or any thickness in a range bounded by, or between, any of these values.

[093] In some embodiments, a yellow emissive layer comprises about 5 to about 6%YE-01 as a dopant in Host-1 .

[094] In some embodiments, the blue emissive layer may comprise the host material DCzDBT, and the red and yellow emissive layers may comprise Host-1 .

[095] A green emissive layer, such as green emissive layer 6 in FIGS. 3C-F, can be phosphorescent or fluorescent. In some embodiments, a green emissive layer can be phosphorescent. A phosphorescent layer can comprise a neat phosphorescent layer, or can comprise a host material and a phosphorescent dopant.

[096] A host material used in a green emissive layer can be any host described above. In some embodiments, the host can be optionally substituted DCzDBT, optionally substituted Host-3, optionally substituted Host-2, optionally substituted Host-1 , or optionally substituted Host-8. In some embodiments, the host can be DCzDBT, Host-3, Host-2, Host- 1 , or Host-8. In some embodiments, the host of a green emissive layer may comprise optionally substituted Host-1 . In some embodiments, the host of a green emissive layer may comprise Host-1 . In some embodiments, the host of a green emissive layer may comprise optionally substituted Host-2. In some embodiments, the host of a green emissive layer may comprise Host-2.

[097] In some embodiments, the green emissive layer has a host that has T1 value higher than 2.5 eV. [098] Any suitable material that emits green light by fluorescence or phosphorescence may be used as a green emissive material, such as a neat green emissive layer or a green emitting dopant. In some embodiments, the green emissive material or dopant is:

Ir(PPy)2(^acac) Ir(mppy)₂(acac) lr(t-Buppy)₂(acac)

(bt)₂lr(lll)(acac) (f-bt)₂lr(lll)(acac) (thp)₂lr(lll)(acac)

bis[2-phenyl bis[2-(4-tert-butylph bis[(2-(2'-thienyl)

benzothiazolato - N,C2'] benzothiazolato-N,C2'] pyridinato-N,C3')] iridium iridium (III) i ri d i u m ( 111 (III) (acetylacetonate)

(acetylacetonate) )(acetylacetonate)

[lr(Flpy)₃] (Cz-CF₃)lr(lll)(acac) (2-

PhPyCz)₂lr(lll)(acac)

tris[2-(9.9- Bis[5-trifluoromethyl-2-[3-(N- dimethylfluoren-2- phenylcarbzolyl)pyridinato- yl)pyridinato- N,C2']iridium(lll)(acetylacetonate)

(N,C3')]iridium (III)

[099] In some embodiments the green emissive layer is doped with lr(ppy)₂acac or lr(ppy)₃.

[0100] For green emitting layers comprising a host and a dopant, any suitable amount of dopant may be used. In some embodiments, the dopant concentration in the green emissive layer may be between about 2 to about 20%, about 2 to about 15%, about 5% to about 10%, or about 6% dopant by weight or volume, or any amount of dopant in a range bounded by, or between, any of these values.

[0101] In some embodiments, the green emissive layer comprises about 6% of a dopant comprising lr(ppy)₃. In some embodiments, a green emissive layer comprises Host-

1 with about 6% by weight or volume of lr(ppy)₃ as dopant. In some embodiments, a green emissive layer comprises Host-2 with about 6% by weight or volume of lr(ppy)₃ as dopant.

[0102] A green emissive layer may have any suitable thickness. In some embodiments, the green emissive layer has a thickness of up to about 10 nm, about 1 nm to about 10 nm, about 3 nm, about 2.5 nm, about 3.5 nm, or any thickness in a range bounded by, or between, any of these values.

[0103] In some embodiments, a green phosphorescent emissive layer is 3.5 nm thick, and comprises Host-1 and 6% by volume (or weight) of lr(ppy)₃ as a dopant. In some embodiments, a green phosphorescent emissive layer is 3.5 nm thick, and comprises Host-

2 and 6% by volume (or weight) of lr(ppy)₃ as a dopant. [0104] An orange emissive layer, such as orange emissive layer 11 in FIGS. 3H and I, can be phosphorescent or fluorescent. In some embodiments, an orange emissive layer can be phosphorescent. A phosphorescent layer can comprise a neat phosphorescent layer, or can comprise a host material and a phosphorescent dopant.

[0105] A host material used in an orange emissive layer can be any host described above. In some embodiments, the host can be optionally substituted DCzDBT, optionally substituted Host-3, optionally substituted Host-2, optionally substituted Host-1 , or optionally substituted Host-8. In some embodiments, the host can be DCzDBT, Host-3, Host-2, Host- 1 , or Host-8. In some embodiments, the host of an orange emissive layer may comprise optionally substituted Host-1 . In some embodiments, the host of an orange emissive layer may comprise Host-1 . In some embodiments, the host of an orange emissive layer may comprise optionally substituted Host-2. In some embodiments, the host of an orange emissive layer may comprise Host-2.

[0106] In some embodiments, the blue, red, and yellow emissive layers have the same host, and the host is Host-1 , Host-6, or Host-8. In some embodiments, the blue, red, and yellow emissive layers have the same host, and the host is Host-1 .

[0107] In some embodiments, a blue emissive layer is fluorescent, and any red, green, yellow, or orange emissive layers are phosphorescent. These phosphorescent layers, taken together, may be thinner than the exciton generation zone, so that the exciton generation zone includes both the phosphorescent and at least part of the fluorescent layer.

[0108] In some embodiments, such as some embodiments represented by FIGS. 3A- 1 , the first blue emissive layer 2 is fluorescent, and any of red emissive layer 4, yellow emissive layer 6, green emissive layer 7, and/or orange emissive layer 11 present in the device are phosphorescent. In some of these devices, carrier mobility of the phosphorescent layers is lower than that of the fluorescent emissive layer, which may allow exciton generation to cover both the fluorescent emissive layer and the phosphorescent emissive layers.

[0109] Other possible emitters include those describe in United States Patent 8,033,229, issued August 23, 201 1 ; United States Patent Application Ser. No. 13/293,537, filed November 10, 201 1 (United States Patent Publication US2012/0121933, published May 17, 2012); United States Application 13/410,812, filed March 2, 2012 (United States Patent Publication No. US2012/0223635, published September 6, 2012); International Patent Application PCT/US2012/054664, WIPO Publication No. WO2013/039914, published March 13, 2013, which are incorporated by reference in their entireties.

[0110] If present, a hole-transport layer, e.g. hole-transport layer 60, may be disposed between the anode and the light-emitting layer. A hole-transport layer may comprise at least one hole-transport material. Hole-transport materials may include, but are not limited to, an aromatic-substituted amine, a carbazole, a polyvinylcarbazole (PVK), e.g. poly(9-vinylcarbazole); polyfluorene; a polyfluorene copolymer; poly(9,9-di-n-octylfluorene- alt-benzothiadiazole); poly(paraphenylene); poly[2-(5-cyano-5-methylhexyloxy)-1 ,4- phenylene]; a benzidine; a phenylenediamine; a phthalocyanine metal complex; a polyacetylene; a polythiophene; a triphenylamine; an oxadiazole; copper phthalocyanine; 1 ,1 -bis(4-bis(4-methylphenyl) aminophenyl) cyclohexane; 2,9-dimethyl-4,7-diphenyl-1 ,10- phenanthroline; 3,5-bis(4-tert-butyl-phenyl)-4-phenyl[1 ,2,4]triazole; 3,4,5-triphenyl-1 ,2,3- triazole; 4,4',4'-tris(3-methylphenylphenylamino)triphenylamine (MTDATA); N,N'-bis(3- methylphenyl)N,N'-diphenyl-[1 ,1 '-biphenyl]-4,4'-diamine (TPD); 4,4'-bis[N-(naphthyl)-N- phenyl-amino]biphenyl (a-NPD); 4,4',4"-tris(carbazol-9-yl)-triphenylamine (TCTA); 4,4'- bis[N,N'-(3-tolyl)amino]-3,3'-dimethylbiphenyl (HMTPD); 4,4'-N,N'-dicarbazole-biphenyl (CBP); 1 ,3-N,N-dicarbazole-benzene (mCP); bis[4-(p,p'-ditolyl-amino)phenyl]diphenylsilane (DTASi); 2,2'-bis(4-carbazolylphenyl)-1 ,1 '-biphenyl (4CzPBP); N,N'N"-1 ,3,5- tricarbazoloylbenzene (tCP); N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine; or the like.

[0111] If present, an electron-transport layer, e.g. electron-transport layer 80, may be disposed between the cathode and the light-emitting layer. Examples of electron-transport materials may include, but are not limited to, 2-(4-biphenylyl)-5-(4-ferf-butylphenyl)-1 ,3,4- oxadiazole (PBD); 1 ,3-bis(N,N-t-butyl-phenyl)-1 ,3,4-oxadiazole (OXD-7), 1 ,3-bis[2-(2,2'- bi pyrid i ne-6-yl )- ,3,4-oxadiazo-5-yl]benzene; 3-phenyl-4-(1 '-naphthyl)-5-phenyl-1 ,2,4- triazole (TAZ); 2,9-dimethyl-4,7-diphenyl-phenanthroline (bathocuproine or BCP); aluminum tris(8-hydroxyquinolate) (Alq3); and 1 ,3,5-tris(2-N-phenylbenzimidazolyl)benzene; 1 ,3-bis[2- (2,2'-bipyridine-6-yl)-1 ,3,4-oxadiazo-5-yl]benzene (BPY-OXD); 3-phenyl-4-(1 '-naphthyl)-5- phenyl-1 ,2,4-triazole (TAZ), 2,9-dimethyl-4,7-diphenyl-phenanthroline (bathocuproine or BCP); and 1 ,3,5-tris[2-N-phenylbenzimidazol-z-yl]benzene (TPBI). In one embodiment, the electron transport layer is aluminum quinolate (Alq₃), 2-(4-biphenylyl)-5-(4-ferf-butylphenyl)- 1 ,3,4-oxadiazole (PBD), phenanthroline, quinoxaline, 1 ,3,5-tris[N-phenylbenzimidazol-z-yl] benzene (TPBI), or a derivative or a combination thereof. [0112] The thickness of an electron-transport layer may of any suitable thickness. For example, some electron-transport layers may have a thickness of about 5 nm to about 200 nm, about 10 nm to about 80 nm, or about 20 nm to about 40 nm.

[0113] An anode, e.g. anode 10, may be a layer comprising a conventional material such as a metal, a mixed metal, an alloy, a metal oxide or a mixed-metal oxide, a conductive polymer, and/or an inorganic material such as a carbon nanotube (CNT). Examples of suitable metals include the Group 1 metals, the metals in Groups 4, 5, 6, and the Group 8-10 transition metals. If the anode layer is to be light-transmitting, metals in Group 10 and 1 1 , such as Au, Pt, and Ag, or alloys thereof; or mixed-metal oxides of Group 12, 13, and 14 metals, such as indium-tin-oxide (ITO), indium-zinc-oxide (IZO), and the like, may be used. In some embodiments, the anode layer may be an organic material such as polyaniline. The use of polyaniline is described in "Flexible light-emitting diodes made from soluble conducting polymer," Nature, vol. 357, pp. 477-479 (1 1 June 1992). In some embodiments, the anode layer may have a thickness in the range of between about 1 nm to about 1000 nm.

[0114] A cathode, e.g. a cathode 30, may be a layer including a material having a lower work function than the anode layer. Examples of suitable materials for the cathode layer include alkali metals of Group 1 , Group 2 metals, Group 12 metals, including rare earth elements, lanthanides and actinides, materials such as aluminum, indium, calcium, barium, samarium and magnesium, and combinations thereof. Li-containing organometallic compounds, LiF, and Li₂0 may also be deposited between the organic layer and the cathode layer to lower the operating voltage. Suitable low work function metals include but are not limited to Al, Ag, Mg, Ca, Cu, Mg/Ag, LiF/AI, CsF, CsF/AI or alloys thereof. In some embodiments, the cathode layer may have a thickness in the range of between about 1 nm to about 1000 nm.

[0115] If present, an electron-injecting layer may be between a cathode layer and an emissive layer. Examples of suitable material(s) that may be included in the electron injecting layer include but are not limited to, an optionally substituted compound selected from the following: aluminum quinolate (Alq₃), 2-(4-biphenylyl)-5-(4-ferf-butylphenyl)-1 ,3,4- oxadiazole (PBD), phenanthroline, quinoxaline, 1 ,3,5-tris[N-phenylbenzimidazol-z-yl] benzene (TPBI) a triazine, a metal chelate of 8-hydroxyquinoline such as tris(8- hydroxyquinoliate) aluminum, and a metal thioxinoid compound such as bis(8- quinolinethiolato) zinc. In one embodiment, the electron injecting layer is aluminum quinolate (Alq₃), 2-(4-biphenylyl)-5-(4-ferf-butylphenyl)-1 ,3,4-oxadiazole (PBD), phenanthroline, quinoxaline, 1 ,3,5-tris[N-phenylbenzimidazol-z-yl] benzene (TPBI), or a derivative or a combination thereof.

[0116] If present, a hole-blocking layer may be between a cathode and a light- emitting layer. Examples of suitable hole-blocking material(s) include but are not limited to, an optionally substituted compound selected from the following: bathocuproine (BCP), 3,4,5-triphenyl-1 ,2,4-triazole, 3,5-bis(4-ferf-butyl-phenyl)-4-phenyl-[1 ,2,4] triazole, 2,9- dimethyl-4,7-diphenyl-1 ,10-phenanthroline, and 1 ,1 -bis(4-bis(4-methylphenyl)aminophenyl)- cyclohexane.

[0117] In some embodiments, a light-emitting device may include an exciton-blocking layer. In an embodiment, the band gap of the material(s) that comprise exciton-blocking layer is large enough to substantially prevent the diffusion of excitons. A number of suitable exciton-blocking materials that may be included in the exciton-blocking layer are known to those skilled in the art. Examples of material(s) that may compose an exciton-blocking layer include an optionally substituted compound selected from the following: aluminum quinolate (Alq₃), 4,4'-bis[N-(naphthyl)-N-phenyl-amino]biphenyl (a-NPD), 4,4'-N,N'-dicarbazole- biphenyl (CBP), and bathocuproine (BCP), and any other material(s) that have a large enough band gap to substantially prevent the diffusion of excitons.

[0118] If present, a hole-injecting layer may be between a light-emitting layer and the anode. Examples of suitable hole-injecting material(s) include, but are not limited to, an optionally substituted compound selected from the following: a polythiophene derivative such as poly(3,4-ethylenedioxythiophene (PEDOT)/polystyrene sulphonic acid (PSS), a benzidine derivative such as N, N, N', N'-tetraphenylbenzidine, poly(N,N'-bis(4-butylphenyl)- N,N'-bis(phenyl)benzidine), a triphenylamine or phenylenediamine derivative such as Ν,Ν'- bis(4-methylphenyl)-N,N'-bis(phenyl)-1 ,4-phenylenediamine, 4,4',4"-tris(N-(naphthylen-2-yl)- N-phenylamino)triphenylamine, an oxadiazole derivative such as 1 ,3-bis(5-(4- diphenylamino)phenyl-1 ,3,4-oxadiazol-2-yl)benzene, a polyacetylene derivative such as poly(1 ,2-bis-benzylthio-acetylene), and a phthalocyanine metal complex derivative such as phthalocyanine copper.

[0119] If present, a light-scattering layer, such as light-scattering layer 130, e.g. nanostructured material may be disposed on: the anode, the cathode, a transparent layer disposed between the anode and the porous film, or a transparent layer disposed between the cathode and the porous film. The nanostructured materials may comprise any nanostructure material described in the following documents:, U.S. Patent Publication No. 2012/0223635 (Ser. No. 13/410,812, filed March 2, 2012, U.S. Patent Application Ser. No. 13/672,394, filed November 8, 2012 and U.S. Provisional Application Ser. No. 61/696,085, filed August 31 , 2012, which is incorporated by reference for their description of appropriate nanostructured materials

[0120] In some embodiments, the device may comprise the following materials:

(a) HOST-1

4,4'-(diphenylsilanediyl)bis(N,N-di-p-tolylaniline)

(b) DTASi, the high-T1 hole transporting material

(c) TPBI the electron transporting material

(d) Yellow emitter YE-01

(e) Red emitter lr(piq)₂acac

(f) Host for red and yellow emitter (Host-1 )

[0121] As used herein, "optionally substituted" group includes its common meaning in the field and includes a group that may be substituted or unsubstituted. A substituted group is derived from the unsubstituted parent structure wherein one or more hydrogen atoms on the parent structure have been independently replaced by one or more substituent groups. A substituted group may have one or more substituents on the parent group structure, in some embodiments, substituents are independently selected from optionally substituted alkyl, -O-alkyl (e.g. -OCH₃, -OC₂H5, -OC₃H₇, -OC₄H₉, etc.), -S-alkyl (e.g. -SCH₃, -SC₂H₅, - SC₃H₇, -SC₄H₉, etc.), -NR'R", -OH, -SH, -CN, -N0₂, or a halogen, wherein R' and R" are independently H or optionally substituted alkyl. Wherever a substituent is described as "optionally substituted," that substituent can be substituted with the above substituents.

[0122] Optionally substituted alkyl includes its common meaning in the field and includes unsubstituted alkyl and substituted alkyl. The substituted alkyl refers to substituted alkyl where one or more H atoms are replaced by one or more substituent groups, such as -O-alkyl (e.g. -OCH₃, -OC₂H5, -OC₃H₇, -OC₄H₉, etc.), -S-alkyl (e.g. -SCH₃, -SC₂H5, - SC₃H₇, -SC₄H₉, etc.), -NR'R" where R' and R" are independently H or alkyl, -OH, -SH, -CN, -N0₂, or a halogen. Some examples of optionally substituted alkyl may be alkyl, haloalkyl, perfluoroalkyl, hydroxyalkyl, alkylthiol (i.e. alkyl-SH), -alkyl-CN, etc.

[0123] Optionally substituted Ci-i₂ alkyl includes its common meaning in the field and includes unsubstituted Ci-i₂ alkyl and substituted Ci-i₂ alkyl. The substituted Ci-i₂ alkyl refers to Ci-i₂ alkyl where one or more hydrogen atoms are independently replaced by one or more of the substituent groups indicated above. [0124] The term "halogen" or "halo" includes its common meaning in the field and includes fluoro, chloro, bromo or iodo.

[0125] The term "fluoroalkyl" includes its common meaning in the field and includes alkyl having one or more fluorine substituents. In other words, it is substituted alkyl where one or more hydrogen atoms are substituted by fluorine, but no other atoms except C, H, and F are present. C1-6F1-13 fluoroalkyl refers to fluoroalkyl having 1 -6 carbon atoms and 1 - 13 fluorine atoms.

[0126] The term "perfluoroalkyl" includes its common meaning in the field and includes fluoroalkyl with a formula C_nF_2n+i for a linear or branched structure, e.g., CF₃, C₂F₅, C₃F₇, C F₉, C5F-1 -1 , C₆F ₃, etc., or C_nF_2n-i for a cyclic structure, e.g., cyclic C₃F₅, cyclic C F₇, cyclic C5F9, cyclic C-6F11 , etc. In other words, every hydrogen atom in alkyl is replaced by fluorine. For example, while not intending to be limiting, C1-3 perfluoroalkyl refers to CF₃, C₂F₅, and C₃F₇ isomers.

[0127] The term "optionally substituted phenyl" includes its common meaning in the field and includes unsubstituted phenyl or substituted phenyl. In substituted phenyl, one or more hydrogen atoms on the ring system are independently replaced by one or more substituent groups indicated above.

[0128] In another embodiment, a white emitting OLED device is provided comprising: a cathode; an anode; and the emissive constructs described above being disposed between the anode and cathode.

[0129] In another embodiment, a white light emitting OLED device is provided comprising in sequence from bottom to top, a substrate; an insulating layer coated on top of the substrate; a reflective and opaque anode above the insulating layer; a hole injection layer above the anode; a hole transport layer above the hole injection layer; the emissive construct described above; an electron transporting layer above the emissive construct; an electron injection layer above the electron transporting layer; a semi transparent or transparent cathode above the electron transport layer; a light emission enhancement layer above the cathode; and a light-scattering layer disposed above the light emission enhancement layer.

[0130] In another embodiment, the light-scattering layer may comprise

3,5-bis(3-(benzo[d]oxazol-2-yl)phenyl)pyridine ("NM-1 ").

[0131] Suitable light-scattering materials include, but are not limited to those described in co-pending applications U.S. Patent Application Ser. No. 13/672,394, filed November 8, 2012; U.S. Patent Application Ser. No. 13/410,812, filed March 2, 2012; and U.S. Provisional Application No. 61/696,085, filed 31 -Aug-2012, which are incorporated by reference herein for all disclosure related to light-scattering or nanostructured compounds. In another embodiment, the light-scattering lens may comprise epoxy material. In some embodiments, the epoxy material may be disposed upon the light-scattering materials described above. In some embodiments, the epoxy material may be substantially hemispherical.

[0132] In some embodiments an outcoupling lens may be employed to increase the luminous efficiency of the device. In some embodiments, the addition of an outcoupling lens can increase the luminous efficiency by from about 10% to about 40%, from about 15% to about 30%, or about 25%, or any percentage increase bounded by, or between any of these values.

[0133] If desired, additional layers may be included in a light-emitting device, such as an electron injecting layer (EIL), a hole-blocking layer (HBL), an exciton-blocking layer (EBL), a hole-injecting layer (HIL), etc. In addition to separate layers, some of these materials may be combined into a single layer.

[0134] Light-emitting devices comprising a subject compound may be fabricated using techniques known in the art, as informed by the guidance provided herein. For example, a glass substrate may be coated with a high work functioning metal such as ITO which may act as an anode. In another example, a glass substrate may be coated with a reflective metal such as Al which may act as an anode. After patterning the anode layer, a hole-injecting and/or hole-transport layer may be deposited on the anode in that order. A light-emitting layer that includes a light-emitting component, may be deposited on the anode, the hole-transport layer, or the hole-injecting layer. The light-emitting layer may contain plural emissive compounds. An electron-transport layer and/or an electron-injecting layer may be deposited in that order on the light-emitting layer. The cathode layer, comprising a low work functioning metal (e.g., Mg:Ag), may then be deposited, e.g., by vapor deposition or sputtering. The device may also contain an exciton-blocking layer, an electron blocking layer, a hole blocking layer, or other layers that may be added to the device using suitable techniques.

[0135] In some embodiments, the outcoupling lens area is from about 2 mm² to about 40 mm², from about 3 mm² to about 10 mm², or about 4 mm², or any area bounded by or between any of these values.

[0136] In some embodiments, the outcoupling lens is hemisphere glass lens.

[0137] In some embodiments, the outcoupling lens has from about a 0.5 cm diameter to about a 10 cm diameter, from about a 1 cm diameter to about a 5 cm diameter, or about a 1 cm diameter, or any diameter bounded by or between any of these values.

[0138] In some embodiments, the outcoupling lens is coupled with refractive index matching oil.

[0139] In some embodiments, the device can have a device power efficiency, measured at 1000 cd/m² (or nit), of from about 25 Im/w to about 300 Im/w, from about 50 Im/w to about 150 Im/w, about 100 Im/w or about 73 Im/w or any power efficiency bounded by or between any of these values.

[0140] In some embodiments, the device can have a working voltage from about 1 volt, to about 500 volts, from about 4 volts to about 20 volts, about 1 volt to about 10 volts, or about 6.5 volts , or about 3.4 volts or any voltage bounded by or between any of these values.

[0141] In some embodiments, the device can have a color accuracy or color rendering index (CRI) of from about -60 to about 100, about 80, about 75, greater than 80, or any CRI bounded by or between any of these values.

[0142] In some embodiments, the device can have a correlated color temperature (CCT) of from about 2000 K to about 7000 K, from about 2500 K to about 4000 K, or about 3000 K, or any CCT bounded by or between any of these values.

[0143] In some embodiments, the resonant layer comprises a material with refractive index greater than 1 .3. In some embodiments, the resonant layer comprises NPB.

[0144] In some embodiments, the resonant layer has the minimal thickness sufficient to match the resonant wavelength of the emissive layers. In some embodiments, the thickness can be sufficient to match the resonant wavelength of the first fluorescent light- emitting layer, the first phosphorescent red emissive layer, the yellow phosphorescent emissive layer, and the second fluorescent light-emitting layer.

[0145] In some embodiments, the resonant layer may have a thickness in the range of between about 10 nm to about 100 nm, about 20 nm to about 80 nm, or about 30 nm to about 50 nm. In some embodiments, the resonant layer may be about 10 nm thick, about 15 nm thick, about 20 nm thick, about 25 nm thick, about 30 nm thick, about 40 nm thick, about 50 nm thick, about 55 nm thick, about 60 nm thick, and/or about 65 nm thick. In some embodiments, the resonant layer may have a thickness between the aforementioned values, or in any combination of the aforementioned values up to about 100 nm. In some embodiments, the resonant layer may be between about 30 nm and about 60 nm thick. In some embodiments, the resonant layer is around 40 nm.

[0146] In some embodiments, the cavity length of TE WOLED (the distance between the inner surface of the anode and the inner surface of the cathode) can at least about 70 nm, at least about 95 nm, at least about 100 nm, at least about 105 nm, at least about 1 10 nm, at least about 1 15 nm, at least about 120 nm; up to about 130 nm, up to about 135 nm, up to about 140 nm, up to about 145 nm, up to about 150 nm, up to about 155 nm, up to about 160 nm, or up to about 165 nm. In some embodiments, the cavity length can be about 1 10 nm to about 150 nm. In some embodiments, the cavity length can be between the aforementioned values, or in any combination of the aforementioned values up to about 165 nm. In some embodiments, wherein the WOLED has an Al anode and a Mg;Ag cathode, the cavity length can be about 130 ± 8 nm, e.g., about 133 nm. In some embodiments, wherein the WOELD has an Ag anode and a Mg:Ag cathode, the cavity length can be about 120 ± 8 nm, e.g., 123 nm.

[0147] The ultra-thin multi-wavelength resonance layer may be used in embodiments comprising an all-phosphor emissive construct, or an emissive construct comprising phosphorescent and fluorescent emissive layers.

[0148] The following non limiting embodiments are contemplated:

Embodiment 1. A top emitting OLED device comprising:

an anode;

a cathode; and

an emissive construct disposed between the anode and cathode.

Embodiment 2. The device of embodiment 1 , wherein the emissive construct comprises,:

a phosphorescent blue emissive layer;

a phosphorescent red emissive layer contacting said phosphorescent blue emissive layer; and

a phosphorescent yellow emissive layer contacting said phosphorescent red emissive layer.

Embodiment 3. The emissive construct of embodiment 2, wherein the phosphorescent blue emissive layer comprises a host material and a dopant material, the phosphorescent red emissive layer comprises a host and a dopant, and the phosphorescent yellow emissive layer comprises a host and a dopant.

Embodiment 4. The emissive construct as in embodiment 3, wherein the phosphorescent blue emissive layer host is a high-T1 host; and wherein the phosphorescent red emissive layer host and the phosphorescent yellow emissive layer host are the same. Embodiment 5. The emissive construct as in embodiment 4, wherein the blue host comprises DCzDBT, and the red and yellow host comprises optionally substituted

Embodiment 6. The emissive construct as in embodiment 3, wherein the blue, red and yellow emissive layers comprises about 5-20% dopant, the red emissive layer dopant comprises lr(piq)2acac, and the yellow emissive layer dopant comprises YE-

01 .

Embodiment 7. The emissive construct as in embodiment 2, wherein the phosphorescent blue emissive layer has a thickness between about 5 nm to about 50 nm, the phosphorescent red emissive layer has a thickness between about 0.1 nm to about 20 nm, and the phosphorescent yellow emissive layer has a thickness between about 5 nm to about 50 nm.

Embodiment s. A device as in embodiment 1 , wherein the emissive construct comprises:

a fluorescent blue emissive layer;

a phosphorescent red emissive layer contacting said fluorescent blue emissive layer; a phosphorescent green layer contacting said phosphorescent red emissive layer; and

a phosphorescent yellow emissive layer contacting said phosphorescent green emissive layer.

Embodiment 9. The emissive construct of embodiment 8, wherein the fluorescent blue emissive layer comprises an ambipolar host material selected from

of a dopant material selected from

Embodiment 10. The emissive construct bodiment 8, wherein the phosphorescent

red emissive layer comprises a host, ^¾s/ , and about 10% of a dopant comprising lr(piq)2acac.

Embodiment 11. The emissive construct of embodiment 8, wherein the phosphorescent

green emissive layer comprises the ho

and about 6% of a dopant comprising lr(ppy)3.

Embodiment 12. The emissive construct of embodiment 8 , wherein the host for the fluorescent blue, phosphorescent red, and phosphorescent yellow layers comprise the same host selected from:

Embodiment 13. The emissive construct as in embodiment 8, wherein the fluorescent emissive layer has a thickness between about 5 nm to about 50 nm, the phosphorescent red emissive layer has a thickness between about 0.1 nm to about 10 nm, the green emissive layer has a thickness about 1 nm to about 10 nm, and the yellow emissive layer has a thickness between about 5 nm to about 50 nm.

Embodiment 14. A device as in embodiment 1 , wherein the emissive construct comprises:

a white light emissive construct comprising a singly doped phosphorescent emissive layer having a peak emissive wavelength between about 500 to about 800 nm; and

a fluorescent blue emissive layer, having a peak emissive wavelength between about 400 to about 500 nm, the phosphorescent emissive layer and the fluorescent emissive layer defining an exciton regeneration zone, the total thickness of the phosphorescent emissive layer is less than the thickness of the exciton regeneration zone.

Embodiment 15. The emissive construct as in embodiment 14, wherein the first phosphorescent emissive layer comprises a singly doped red emissive layer and the second phosphorescent emissive layer comprises a singly doped yellow emissive layer. Embodiment 16. The emissive construct as in embodiment 14, wherein the first phosphorescent emissive layer comprises a singly doped red emissive layer and the second phosphorescent emissive layer comprises a singly doped green emissive layer.

Embodiment 17. The emissive construct as in embodiment 14, further comprising a second fluorescent emissive layer, and wherein the total thickness of the phosphorescent emissive layer[s] is less than 10 nm, wherein the carrier mobility in the phosphorescent emissive layer is less than the carrier mobility in the fluorescent emissive layer, defining an exciton generation zone which covers both the fluorescent emissive layer and phosphorescent emissive layer.

Embodiment 18. The emissive construct as in embodiment 14, wherein the phosphorescent emissive layer comprises a host material and a single emitter material, the host material having a higher T1 than the emitter material T1 .

Embodiment 19. The emissive construct as in embodiment 14, wherein the fluorescent emissive layer comprises a host and a single blue emitter, the host and emitter having higher T1 than the T1 of the phosphorescent emitters in the phosphorescent emissive layer.

Embodiment 20. A device as in embodiment 1 , further comprising: a multi-wavelength resonant layer, comprising a material having a refractive index less than 1 .3 and having a thickness sufficient to match the resonant wavelength of the peak emission(s) from the layer(s) of the emissive construct, and disposed on the side of the cathode opposite the emissive construct.

Example 1

[0149] Device A1 was prepared having a structure consistent with that depicted in FIG. 2. A 40 nm SiN insulating later was coated on top of the glass substrate, then 50 nm Al followed by 50 nm Ag layer for the anode, on top of the Ag anode, 10 nm thick M0O₃ was deposited as the HIL and the HTL consists of 30 nm NPB and 15 nm DTASi, 10 nm phosphor-Blue EML with 12% doping (DCzDBT as the host, PBE-7 as the blue emitter). Red-EML is 1 nm thick, 10% doping of lr(piq)₂acac in Host-1 host, Yellow-EML is 30 nm thick YE-01 as the yellow emitter with 6% doping concentration in Host-1 host. TPBI as the ETL with 30 nm thickness, LiF as the EIL with 1 nm thickness, the cathode consists of mixture of Mg:Ag with 1 :3 ratio in the total thickness of 20 nm. The capping layer consist of ZnS with 85 nm thickness.

[0150] In some embodiments, white light can be emitted from Device A1 when a light-scattering film is attached to the capping layer with refractive index matching oil (FIG. 4). FIG. 4 shows the setup to measure the electroluminescence spectrum. With the diffuser film, all the colors mixed together and have a uniform white color output. FIG. 5 Shows the EL spectrum of a device. CRI(75), CIE(0.436, 0.446).

[0151] FIG. 6 shows the brightness dependence of the power efficiency of Device A1 with and without macro outcoupling lens. The device area is 4 mm², macro lens is hemisphere glass lens with 1 cm diameter, coupled with refractive index matching oil (n=1 .5)

[0152] FIG. 7 show the brightness dependence of the Device A1 power external quantum efficiency (EQE) with and without macro outcoupling lens. The device area is 4 mm², macro lens is hemisphere glass lens with 1 cm diameter, coupled with refractive index matching oil (n=1 .5)

Example 2: Device fabrication

[0153] Device A2 was prepared having a structure consistent with that depicted in FIGS. 8 and 9. Pre-cleaned glass substrates with 40 nm thick SiN covered layer, were baked at about 200 °C for about 1 hour under ambient environment, then under UV-ozone treatment for about 30 minutes. The substrates were loaded into a deposition chamber. A reflective bottom anode, (100 nm Al layer) was deposited at a rate of about 2 A/s. Molybdenum oxide (M0O₃, about 5 nm) was deposited as a hole-injecting layer at deposition rate of about 1 A/s. Then a p-doping layer (10 nm), M0O₃ was co-deposited with 4,4'-bis[N-(naphthyl)-N-phenyl-amino]biphenyl (NPB) at 10% in volume ratio at the deposition rate of about 0.1 A /s and about 1 .0 A /s for M0O₃ and NPB, respectively. A layer of NPB (about 30 nm) was then deposited as a hole-transport layer. A first fluorescent blue emissive layer (15 nm) was then deposited having a fluorescent blue emitter (BE-3) that was co-deposited with a host material (Host-1 ) at 6% in volume with the deposition rate of about 0.05 A/s for BE-3 and about 1 A/s for Host-1 .

Host-1

[0154] Then deposition of the red phosphorescent emissive layer (1 nm) of co- deposition of host (Host-1 ) with red emitter (lr(piq)₂acac, 10%) at the deposition rate of about 1 A/s for Host-1 , and about 0.005 A/s for lr(pq)₂acac. Then deposition of the green phosphorescent emissive layer (3.5 nm) of co-deposition of host (Host-1 ) with green emitter (lr(ppy)₃, 6%) at the deposition rate of about 1 A/s for Host-2, and about 0.005 A/s for lr(pq)₂acac.

Host-2

[0155] Then deposition of the third phosphorescent layer (30 nm) of co-deposition of host (Host-1 ) with yellow emitter (YE-01 ) at a deposition rate of about 1 A/s for Host-1 and about 0.05 A/s for YE-01 .

lr(pq)₂acac lr(ppy)₃

[0156] The doping concentration of the red emitter was about 10 volume%, the doping concentration of the yellow emitter and the green emitter were about 6 volume% and about 6 volume%, respectively. Next, an electron transport layer (TPBI) of about 30 nm was deposited at the deposition rate of about 1 A/s. The electron injection layer was then deposited as a thin layer of lithium fluoride (LiF, 1 nm thick, deposition rate 0.1 A/s). A semi-transparent cathode (about 20 nm) was deposited by co-deposition of magnesium (Mg) and silver (Ag) at a ratio of about 1 :3 by volume. A capping layer (NPB) was then deposited at a deposition rate of about 0.1 A/s. Finally a light-scattering layer of nanostructured material (3,5-bis(3-(benzo[d]oxazol-2-yl)phenyl)pyridine) was deposited on top of the light enhancement layer at deposition rate of about 2 A/s for 600 nm. All the deposition was done at a base pressure of about 2 x 10^"7 torr. The device area was approximately 7.7 mm².

3,5-bis(3-(benzo[d]oxazol-2-yl)phenyl)pyridine

[0157] Additional devices (A3 [3.0 nm green layer] and A4 [2.5 nm green layer]) were constructed in the same manner, except that the thickness of the phosphorescent green emissive layer ( the second phosphorescent layer) was varied as indicated in Table -2.

[0158] In addition, additional devices (B-2, B-3, and B-4) were constructed in the same manner as above, except that an additional substantially hemispherical layer formed by a drop of epoxy substantially covering the entire surface of the device was disposed atop the NM-1 layer.

[0159] FIG. 10 shows the electroluminescence (EL) spectrum (CRI 75, CIE(0.47, 0.44) of Device A2 at 1000 nit. FIG. 1 1 shows the device performance data, brightness dependence of the power efficiency and current efficiency of Device A2 at 1000 nit, 85 Im/w, 86 cd/A, and 32% EQE.

[0160] FIG. 12 shows the brightness over time of operation of Device B2 (Device A2 with outcoupling hemispherical layer) with an initial brightness of 35000 nit and an acceleration factor of 1 .6, the device showed a LT70 of about 7500h at 1000 nit. FIG. 1 1 shows the device performance data, brightness dependence of the power efficiency and current efficiency of Device B2 at 1000 nit, 85 Im/w, 86 cd/A, and 32% EQE.

Example 3

[0161] Devices A4 and A3 were prepared using the same fabrication procedure as Device A2 (FIGS. 7-8) except the thickness of the phosphorescent green emitting layer 16 was 2.5 nm, 3.0 nm respectively. The EL spectrums of the devices were compared to discern the effect of the thickness of the green layer upon the EL spectrum. FIGS. 15 (CRI 55, CIE(0.56, 0.45)) and 14 (CRI 64, CIE(0.48, 0.45)) show the electroluminescence (EL) spectrum of Devices A4 and A3 respectively, at 1000 nit. A change in thickness of the green phosphorescent emissive layer 16 from 2.5 nm (Device A4 ), with a perceived peak blue emission of about 0.2 EL and a peak red emissive peak of about 0.8 EL (see FIG. 15), to a thickness of the green phosphorescent emissive layer 16 to about 3.5 nm (Device A2), resulted a perceived peak blue emission of about 0.3 EL and a peak red emissive peak of about 1 .0 EL (see FIG. 10). The perceived changes in the peak emissions were about 0.2 (Device A4) to 0.3 EL (Device A2) for the blue emissive peak and about 0.8 (Device A4) to about 1 .0 EL (Device A2) for the red emissive peak. The perceived changes in the CRI values were about 55 (Device A4) to 64 (Device A3) to 75 (Device A2).

[0162] The results at 1000 cd/m² are also summarized in Table 2.

Table 2

Example-4

[0163] Device 3 (All-phosphor TE-WOELD), Device 4 (4-color hydrid E-WOELD) and Device 5 (3-color hybrid TE-WOELD) were made in a manner similar to that described for Example 1 , except that FBE-1 was used as the fluorescent blue emitter instead of PBE-7. With a 40 nm capping layer, the device showed a very nice EL spectrum and very small angular dependence (FIG. 9)

Experimental of Devices fabrication [0164] There are several type devices in this application, (1 ) the All-phosphor TE- WOLED,(2) the 4-color hybrid TE-WOLD and (3) 3-color Hybrid-TE-WOLED. There are some common parts in the device fabrication on the substrates, anode deposition, hole- injection layer, electron transporting layer and cathode. The device fabrication processes generally have the same sequence as their device structure order, e.g., starting from Hole- injection layer (HIL), hole transporting layer (HTL), emissive layer (EML) and electron injection and cathode layer, the final is the capping layer on top of semitransparent cathodes.

Common process:

[0165] The pre-cleaned glass substrates with 40 nm-thick SiN layer were baked at about 200 °C for about 1 hour under ambient environment, then under UV-ozone treatment for about 30 minutes. The substrates were loaded into a deposition chamber. A bi-layer reflective bottom anode, (50 nm Al layer and 50 nm Ag layer) was deposited sequentially, first Al then Ag, at a rate of about 2 A/s. Molybdenum oxide (M0O₃, about 10 nm) was deposited as a hole-injecting layer at deposition rate of 1 A/s.

[0166] Followed by HTL and EML construction, that had some differences between the devices.

[0167] After the respective construction through the HTL and EML, the device construction then followed with the deposition of the electron transport layer (TPBI) of about 30 nm at the deposition rate of 1 A/s. Then the deposition of the electron injection layer followed, by the deposition of a thin layer of lithium fluoride (LiF, 1 nm thick, deposition rate 0.1 A/s) and a co-deposition of magnesium (Mg) and silver (Ag) at a ratio of about 1 :3 by volume for a total Mg/Ag layer thickness of about 20 nm. A capping layer (85 nm) of ZnS was then deposited atop the semi-transparent cathodes. All the deposition was done at a base pressure of about 2 x 10^"7 torr. The device area was about 4 mm².

For the All PH-WOLED devices,

[0168] After the construction of the hole injection layer, a p-doping layer (10 nm), M0O₃ was co-deposited with NPB at 5% in volume ratio at the deposition rate of 0.05 and 1A /s for M0O₃ and NPB, respectively. Then a layer of NPB (30 nm) was deposited. Followed by the deposition of the Phosphorescent blue emissive layer (8 nm), of co- deposition of phosphor blue emitter (PBE-7) and phosphorescent blue host (DCzDBT) with 12% volume ratio where 0.1 A/s for PBE-7 and 1 A/s for DCzDBT. Then deposition of the red phosphorescent emissive layer (1 nm) of co-deposition of host (Host-1 ) red emitter of lr(pq)₂acac at the deposition rate of 1 A/s, and 0.005 A/s, the doping concentration of the red emitter was 10% by volume. Then deposition of the yellow phosphorescent emissive layer (30 nm) of co-deposition of host ( Host-1 ) and yellow emitter YE-01 at the deposition rate of 1 A/s, and 0.005 A/s, the doping concentration of the yellow emitter was 6% by volume. Followed common deposition of the ETL, EIL and cathode. A capping layer (85 nm) of ZnS was then deposited atop the semi-transparent cathodes.

For the 4-color hybrid TE-WOELD

[0169] After the deposition of the hole injection layer, a p-doping layer (10 nm), M0O₃ was co-deposited with NPB at 5% in volume ratio at the deposition rate of 0.05 and 1A /s for M0O₃ and NPB, respectively, and then a layer of NPB (30 nm) were deposited. Followed by the deposition of the fluorescent blue emissive layer (15 nm), fluorescent blue emitter (BE-3) was co-deposited with the host material (Host-1 ) at 6% in volume with the deposition rate of 0.1 A/s for BE-3 and 1 A/s for Host-1 . Followed by the deposition of the phosphorescent red emissive layer (1 nm), phosphorescent red emitter (lr(piq)2acac) was co-deposited with the host material (Host-1 ) at 10% in volume with the deposition rate of 0.1 A/s for lr(piq)₂acac and 1 A/s for Host-1 . Followed by the deposition of the phosphorescent green emissive layer (3.5 nm), phosphorescent green emitter (lr(ppy)₃ was co-deposited with the host material (Host-2) at 6% in volume with the deposition rate of 0.1 A/s for lr(ppy)3 and 1 A/s for Host-2. Followed by the deposition of the phosphorescent yellow emissive layer (30 nm), phosphorescent yellow emitter (YE-01 ) was co-deposited with the host material (Host-1 ) at 6% in volume with the deposition rate of 0.1 A/s for YE-01 and 1 A/s for Host-1 .

[0170] Then, the common deposition of ETL, EIL and cathode. A capping layer of NPB (80 nm) was deposited on top of the cathode.

For the 3-color Hybrid-TE-WOLED with ultrathin resonant capping layer (FIG.23)

[0171] Then a p-doping layer (10 nm), M0O₃ was co-deposited with NPB at 5% in volume ratio at the deposition rate of 0.05 and 1 A/s for M0O3 and NPB, respectively. A layer of NPB (about 10 nm) was then deposited as a hole-transport layer. Followed by the deposition of the fluorescent blue emissive layer (20 nm), fluorescent blue emitter (BE-5) was co-deposited with the host material (Host-1 ) at 7% in volume with the deposition rate of 0.07 A/s for BE-5 and 1 A/s for Host-1 . Then followed by the deposition of phosphorescent emissive layer, consists of a red and yellow emissive layer. The red phosphorescent emissive layer (1 nm, lr(piq)₂acac doped in host-1 at 5% in volume) was deposited on top of the blue fluorescent emissive layer by deposition rate of 0.005 and 1 A/s for the lr(piq)₂acac and Host-1 , respectively. The yellow phosphorescent emissive layer (4 nm, YE- 01 doped in Host-1 at 5% in volume) was deposited on top of the red phosphorescent emissive layer by deposition rate of 0.05 and 1 A/s for the YE-01 and Host-1 , respectively. Then another Fluorescent blue emissive layer (20 nm, BE-5 co-deposited with Host-1 at 7% in volume ratio) was deposited on top of the phosphorescent yellow emissive layer to finish the emissive layer deposition.

[0172] Followed by the common deposition of ETL, EIL and cathode as described above.

[0173] The EL spectrum of the device with various thickness of the NPB capping layer and with different viewing angles (0° and 60°) are shown in FIGs. 24-29

Example 5: Device operation

[0174] The electroluminescence spectrum of Example 1 was measured. FIG. 2 shows an EL spectrum of a TE-WOLED embodiment at lower (2000 nit) and higher brightness (10000 nit) with CIE(0.44, 0.36), CRI(65). As shown in FIG. 2, the hole-blocking layer effectively confines the charge recombination center at the interface between the orange and blue emissive layers, giving stable emissive color at higher brightness.

[0175] The brightness dependence of the current efficiency and power efficiency of Example 1 was also measured. FIG. 3 shows the brightness dependence of current efficiency and power efficiency of an embodiment of a white TE-OLED device.

[0176] FIG. 4 shows the brightness level over the lifetime of a device in accordance with Example 1 , except the substrate was PEDOT coated with ITO/Glass. FIG. 5 shows the brightness level over the lifetime of Example 1 . As shown in FIGs. 4 and 5, the device lifetime and stability is improved using the more simplified substrate of PMMA coated with glass.

[0177] The CRI and CIR of the EL spectra (FIGs. 24-29) of the Device 5-type with varying capping layer thicknesses (ZnS) are depicted in Table-1 below. Table-1

[0178] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0179] The terms "a," "an," "the" and similar referents used in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. All methods described herein may be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of any claim. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0180] Groupings of alternative elements or embodiments disclosed herein are not to be construed as limitations. Each group member may be referred to and claimed individually or in any combination with other members of the group or other elements found herein. It is anticipated that one or more members of a group may be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

[0181] Certain embodiments are described herein, including the best mode known to the inventors for carrying out the invention. Of course, variations on these described embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventor expects skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than specifically described herein. Accordingly, the claims include all modifications and equivalents of the subject matter recited in the claims as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is contemplated unless otherwise indicated herein or otherwise clearly contradicted by context.

[0182] In closing, it is to be understood that the embodiments disclosed herein are illustrative of the principles of the claims. Other modifications that may be employed are within the scope of the claims. Thus, by way of example, but not of limitation, alternative embodiments may be utilized in accordance with the teachings herein. Accordingly, the claims are not limited to embodiments precisely as shown and described.

Claims

WHAT IS CLAIMED IS:

1. A top emitting OLED device comprising:

an anode;

a cathode; and

an emissive construct disposed between the anode and cathode;

wherein the emissive construct comprises:

a first blue emissive layer, wherein the first blue emissive layer is phosphorescent or fluorescent;

a red emissive layer contacting the first blue emissive layer, wherein the red emissive layer is phosphorescent; and

either

(A) a yellow emissive layer contacting the red emissive layer; or

(B) a green emissive layer contacting the red emissive layer, and a yellow emissive layer contacting the green emissive layer;

wherein the yellow emissive layer is phosphorescent and the green emissive layer, if present, is phosphorescent.

2. The device of claim 1 , wherein the first blue emissive layer is disposed between the anode and the red emissive layer.

3. The device of claim 1 , comprising the yellow emissive layer contacting the red emissive layer.

4. The device of claim 1 , wherein the green emissive layer contacting the red emissive layer, and the yellow emissive layer contacting the green emissive layer.

5. The device of claim 1 , wherein the first blue emissive layer comprises a host material and a dopant material, the red emissive layer comprises a host and a dopant, the green emissive layer, when present, comprises a host and a dopant, and the yellow emissive layer comprises a host and a dopant.

6. The device of claim 5, wherein the first blue emissive layer comprises a host with a high T1 ; and wherein the red emissive layer and the yellow emissive layer have the same host.

7. The device of claim 6, wherein the blue emissive layer comprises DCzDBT as a comprises optionally substituted

8. The device of claim 5, wherein the blue, red and yellow emissive layers comprise about 5 to about 20% dopant, the dopant of the red emissive layer comprises lr(piq)₂acac, and the dopant of the yellow emissive layer comprises YE-01 .

9. The device of claim 1 , wherein the blue emissive layer has a thickness between about 5 nm to about 50 nm, the red emissive layer has a thickness between about 0.1 nm to about 20 nm, and the yellow emissive layer has a thickness between about 5 nm to about 50 nm.

n the red emissive layer

a host and about 10% of lr(piq)₂acac as a dopant.

m 1 , wherein the green emissive layer comprises

as a host and about 6% of lr(ppy)₃ as a dopant.

13. The device of claim 1 , wherein the blue emissive layer, red emissive layer, and yellow emissive layer have the same host, and the host is

14. The device of claim 4, wherein the blue emissive layer has a thickness between about 5 nm to about 50 nm, the red emissive layer has a thickness between about 0.1 nm to about 10 nm, the green emissive layer has a thickness of about 1 nm to about 10 nm, and the yellow emissive layer has a thickness between about 5 nm to about 50 nm.

15. An OLED device comprising:

an anode; a cathode; and

an emissive construct disposed between the anode and cathode;

wherein the emissive construct comprises:

a phosphorescent emissive layer that is singly doped and has a peak emissive wavelength between about 500 to about 800 nm; and

a first fluorescent emissive layer, having a peak emissive wavelength between about 400 to about 500 nm.

16. The device of claim 15, wherein the emissive construct further comprises an exciton regeneration zone that overlaps with both the phosphorescent emissive layer and the fluorescent emissive layer, and the total thickness of the phosphorescent emissive layer is less than the thickness of the exciton regeneration zone.

17. The device of claim 15, wherein the phosphorescent emissive layer is a red phosphorescent emissive layer, and the emissive construct further comprises a yellow phosphorescent emissive layer that is singly doped and in contact with the red phosphorescent emissive layer.

18. The device of claim 15, wherein the phosphorescent emissive layer is a red phosphorescent emissive layer, and the emissive construct further comprises a green phosphorescent emissive layer that is singly doped and in contact with the red phosphorescent emissive layer.

19. The device of claim 15, further comprising a second fluorescent emissive layer, and wherein the total thickness of all phosphorescent emissive layers is less than 10 nm, wherein the carrier mobility in all phosphorescent emissive layers is less than the carrier mobility in the first fluorescent emissive layer, and wherein the emissive construct further comprises an exciton regeneration zone which overlaps with all of the phosphorescent emissive layers and the fluorescent emissive layer, and the total thickness of all phosphorescent emissive layers is less than the thickness of the exciton regeneration zone.

20. The device of claim 15, wherein the phosphorescent emissive layer comprises a host material and a single emitter material, the host material having a higher T1 than the emitter material T1 .

21. The device of claim 15, wherein the fluorescent emissive layer comprises a host and a single blue emitter, wherein the host of the fluorescent emissive layer and the blue emitter of the fluorescent emissive layer have a higher T1 than the T1 of the phosphorescent emitter in the phosphorescent emissive layer.

22. The device of claim 1 , wherein the first blue emissive layer is phosphorescent.

23. The device of claim 1 , wherein the first blue emissive layer is fluorescent.

24. The device of claim 1 , further comprising a second blue emissive layer contacting the yellow emissive layer, wherein the second blue emissive layer is fluorescent.

25. The device of claim 1 , wherein the emissive construct comprises

a first blue emissive layer, wherein the first blue emissive layer is phosphorescent or fluorescent;

a red emissive layer contacting the first blue emissive layer, wherein the red emissive layer is phosphorescent;

a yellow emissive layer contacting the red emissive layer, wherein the yellow emissive layer is phosphorescent; and

a second blue emissive layer contacting the yellow emissive layer, wherein the second blue emissive layer is phosphorescent or fluorescent.

26. An OLED device comprises

an anode;

a cathode; and

an emissive construct between the anode and cathode,

wherein the emissive construct comprises:

a first blue emissive layer, wherein the first blue emissive layer is phosphorescent or fluorescent;

a red emissive layer contacting the first blue emissive layer, wherein the red emissive layer is phosphorescent;

a green emissive layer contacting the red emissive layer, wherein the green emissive layer is phosphorescent; and a second blue emissive layer contacting the green emissive layer, wherein the second blue emissive layer is phosphorescent or fluorescent.

27. An OLED device comprising:

an anode;

a cathode; and

an emissive construct disposed between the anode and cathode;

wherein the emissive construct comprises:

a first blue emissive layer, wherein the first blue emissive layer is phosphorescent or fluorescent;

a red emissive layer contacting the first blue emissive layer, wherein the red emissive layer is phosphorescent;

a green emissive layer contacting the red emissive layer; and wherein the green emissive layer is phosphorescent.

28. An OLED device comprising:

an anode;

a cathode; and

an emissive construct disposed between the anode and cathode;

wherein the emissive construct comprises;

a first blue emissive layer, wherein the first blue emissive layer is phosphorescent or fluorescent;

an orange emissive layer contacting the first blue emissive layer; and wherein the orange emissive layer is phosphorescent.

29. The device of claim 29, further comprising a second blue emissive layer contacting the orange emissive layer, wherein the blue emissive layer is phosphorescent or fluorescent.

30. A light-emitting device comprising an anode, a cathode, an emissive construct disposed between the anode and the cathode, and a multi-wavelength resonant layer, wherein the multi-wavelength resonance layer comprises a material having a refractive index less than 1 .3 and has a thickness sufficient to match the resonant wavelength of the peak emission from the emissive construct, and the multi-wavelength resonant layer is disposed on the side of the cathode opposite the emissive construct.

31. The device of claim 31 , wherein the multi-wavelength resonant layer has a thickness of about 30 nm to about 50 nm.

32. The device of claim 31 , wherein the anode has an inner surface and the cathode has an inner surface, and the distance between the inner surface of the anode and the inner surface of the cathode is about 90 nm to about 170 nm.