U.S. patent application number 17/410425 was filed with the patent office on 2022-03-31 for high color gamut oled displays.
The applicant listed for this patent is Universal Display Corporation. Invention is credited to Julia J. BROWN, Michael HACK, Michael Stuart WEAVER.
Application Number | 20220102441 17/410425 |
Document ID | / |
Family ID | 1000005971998 |
Filed Date | 2022-03-31 |
United States Patent
Application |
20220102441 |
Kind Code |
A1 |
HACK; Michael ; et
al. |
March 31, 2022 |
High Color Gamut OLED Displays
Abstract
Devices, arrangements, and techniques are provided to improve
the color saturation of displays such as OLED displays while
avoiding or substantially reducing any increase in power
consumption that typically would be associated with such increase
in saturation. A three-subpixel per pixel red/green/blue (RGB)
architecture is provided as well as a four sub-pixel approach which
uses two red sub-pixels for each pixel (red/red/green/blue, or
R1R2GB).
Inventors: |
HACK; Michael; (Carmel,
CA) ; WEAVER; Michael Stuart; (Princeton, NJ)
; BROWN; Julia J.; (Yardley, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Universal Display Corporation |
Ewing |
NJ |
US |
|
|
Family ID: |
1000005971998 |
Appl. No.: |
17/410425 |
Filed: |
August 24, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
63085015 |
Sep 29, 2020 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 27/3218 20130101;
H01L 51/5265 20130101; H01L 51/502 20130101; H01L 27/322 20130101;
H01L 27/3276 20130101; H01L 27/3213 20130101 |
International
Class: |
H01L 27/32 20060101
H01L027/32; H01L 51/52 20060101 H01L051/52; H01L 51/50 20060101
H01L051/50 |
Claims
1. A device comprising: a full-color display panel comprising a
plurality of pixels, each comprising one or more sub-pixels, at
least one of the plurality of pixels comprising: a green sub-pixel;
a blue sub-pixel; a first red sub-pixel; and a second red sub-pixel
having a different emission spectrum than the first red
sub-pixel.
2. The device of claim 1, wherein the at least one pixel includes
no sub-pixels other than the green, blue, first red, and second red
sub-pixels.
3. The device of claim 1, wherein the first and second red
sub-pixels have 1931 CIE x coordinates that differ by at least
0.02.
4. (canceled)
5. (canceled)
6. The device of claim 1, wherein when the full-color display panel
displays an image using the green, blue, and first red sub-pixels,
the at least one pixel uses not more than 10% more power than when
the full-color display panel displays the same image using the
green, blue, and second red sub-pixels.
7. (canceled)
8. The device of claim 1, wherein at least one of the green
sub-pixel, blue sub-pixel, first red sub-pixel, and second red
sub-pixel comprises an organic light emitting diode (OLED).
9. (canceled)
10. The device of claim 1, wherein the second red sub-pixel
comprises a cavity structure.
11. The device of claim 1, wherein the first red sub-pixel
comprises a cavity structure.
12. (canceled)
13. The device of claim 1, wherein the first and second red
sub-pixel comprise different emissive materials.
14. The device of claim 1, further comprising a color filter in
optical communication with the first red sub-pixel.
15. The device of claim 1, wherein the first red sub-pixel
comprises a first emissive material and a first quantum dot
down-conversion layer.
16. The device of claim 15, wherein the first emissive material is
a blue, light blue, green emissive material or a combination
thereof.
17. The device of claim 15, wherein the second red sub-pixel
comprises the first emissive material and a second quantum dot
down-conversion layer.
18. The device of claim 1, wherein the display panel comprises 3
data lines per pixel.
19. The device of claim 1, wherein the first and second red
sub-pixels comprise a common emissive layer.
20. The device of claim 19, wherein the first and second red
sub-pixels comprise different cavity structures.
21. The device of claim 19, wherein the first and second red
sub-pixels comprise different quantum dot down-conversion
layers.
22. The device of claim 1, wherein the display panel is capable of
operating with a color gamut equivalent to at least 95% of the
Rec2020 1931 CIE color gamut with a power consumption of not more
than 6.85 mW/cm.sup.2 at 500 nits luminance.
23. (canceled)
24. The device of claim 1, wherein the display panel is capable of
operating with a color gamut equivalent to at least 90% of the
Rec2020 1931 CIE color gamut with a power consumption of not more
than 6 mW/cm.sup.2 at 500 nits luminance.
25. (canceled)
26. A consumer electronic device comprising: a full-color display
panel comprising a plurality of pixels, each comprising one or more
sub-pixels, at least one of the plurality of pixels comprising: a
green sub-pixel; a blue sub-pixel; a first red sub-pixel; and a
second red sub-pixel having a different emission spectrum than the
first red sub-pixel.
27. The consumer electronic device of claim 26, wherein the product
comprises at least one type selected from the group consisting of:
a flat panel display, a curved display, a computer monitor, a
medical monitor, a television, a billboard, a light for interior or
exterior illumination and/or signaling, a heads-up display, a fully
or partially transparent display, a flexible display, a rollable
display, a foldable display, a stretchable display, a laser
printer, a telephone, a cell phone, tablet, a phablet, a personal
digital assistant (PDA), a wearable device, a laptop computer, a
digital camera, a camcorder, a viewfinder, a micro-display that is
less than 2 inches diagonal, a 3-D display, a virtual reality or
augmented reality display, a vehicle, a video walls comprising
multiple displays tiled together, a theater or stadium screen, and
a sign.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a non-provisional of and claims the
priority benefit of U.S. Provisional Patent Application Ser. No.
63/085,015, filed Sep. 29, 2020, the entire contents of which are
incorporated herein by reference.
FIELD
[0002] The present invention relates to devices and techniques for
fabricating organic emissive devices, such as organic light
emitting diodes, having high color gamut, and devices and
techniques including the same.
BACKGROUND
[0003] Opto-electronic devices that make use of organic materials
are becoming increasingly desirable for a number of reasons. Many
of the materials used to make such devices are relatively
inexpensive, so organic opto-electronic devices have the potential
for cost advantages over inorganic devices. In addition, the
inherent properties of organic materials, such as their
flexibility, may make them well suited for particular applications
such as fabrication on a flexible substrate. Examples of organic
opto-electronic devices include organic light emitting
diodes/devices (OLEDs), organic phototransistors, organic
photovoltaic cells, and organic photodetectors. For OLEDs, the
organic materials may have performance advantages over conventional
materials. For example, the wavelength at which an organic emissive
layer emits light may generally be readily tuned with appropriate
dopants.
[0004] OLEDs make use of thin organic films that emit light when
voltage is applied across the device. OLEDs are becoming an
increasingly interesting technology for use in applications such as
flat panel displays, illumination, and backlighting. Several OLED
materials and configurations are described in U.S. Pat. Nos.
5,844,363, 6,303,238, and 5,707,745, which are incorporated herein
by reference in their entirety.
[0005] One application for phosphorescent emissive molecules is a
full color display. Industry standards for such a display call for
pixels adapted to emit particular colors, referred to as
"saturated" colors. In particular, these standards call for
saturated red, green, and blue pixels. Alternatively the OLED can
be designed to emit white light. In conventional liquid crystal
displays emission from a white backlight is filtered using
absorption filters to produce red, green and blue emission. The
same technique can also be used with OLEDs. The white OLED can be
either a single EML device or a stack structure. Color may be
measured using CIE coordinates, which are well known to the
art.
[0006] As used herein, the term "organic" includes polymeric
materials as well as small molecule organic materials that may be
used to fabricate organic opto-electronic devices. "Small molecule"
refers to any organic material that is not a polymer, and "small
molecules" may actually be quite large. Small molecules may include
repeat units in some circumstances. For example, using a long chain
alkyl group as a substituent does not remove a molecule from the
"small molecule" class. Small molecules may also be incorporated
into polymers, for example as a pendent group on a polymer backbone
or as a part of the backbone. Small molecules may also serve as the
core moiety of a dendrimer, which consists of a series of chemical
shells built on the core moiety. The core moiety of a dendrimer may
be a fluorescent or phosphorescent small molecule emitter. A
dendrimer may be a "small molecule," and it is believed that all
dendrimers currently used in the field of OLEDs are small
molecules.
[0007] As used herein, "top" means furthest away from the
substrate, while "bottom" means closest to the substrate. Where a
first layer is described as "disposed over" a second layer, the
first layer is disposed further away from substrate. There may be
other layers between the first and second layer, unless it is
specified that the first layer is "in contact with" the second
layer. For example, a cathode may be described as "disposed over"
an anode, even though there are various organic layers in
between.
[0008] As used herein, "solution processible" means capable of
being dissolved, dispersed, or transported in and/or deposited from
a liquid medium, either in solution or suspension form.
[0009] A ligand may be referred to as "photoactive" when it is
believed that the ligand directly contributes to the photoactive
properties of an emissive material. A ligand may be referred to as
"ancillary" when it is believed that the ligand does not contribute
to the photoactive properties of an emissive material, although an
ancillary ligand may alter the properties of a photoactive
ligand.
[0010] As used herein, and as would be generally understood by one
skilled in the art, a first "Highest Occupied Molecular Orbital"
(HOMO) or "Lowest Unoccupied Molecular Orbital" (LUMO) energy level
is "greater than" or "higher than" a second HOMO or LUMO energy
level if the first energy level is closer to the vacuum energy
level. Since ionization potentials (IP) are measured as a negative
energy relative to a vacuum level, a higher HOMO energy level
corresponds to an IP having a smaller absolute value (an IP that is
less negative). Similarly, a higher LUMO energy level corresponds
to an electron affinity (EA) having a smaller absolute value (an EA
that is less negative). On a conventional energy level diagram,
with the vacuum level at the top, the LUMO energy level of a
material is higher than the HOMO energy level of the same material.
A "higher" HOMO or LUMO energy level appears closer to the top of
such a diagram than a "lower" HOMO or LUMO energy level.
[0011] As used herein, and as would be generally understood by one
skilled in the art, a first work function is "greater than" or
"higher than" a second work function if the first work function has
a higher absolute value. Because work functions are generally
measured as negative numbers relative to vacuum level, this means
that a "higher" work function is more negative. On a conventional
energy level diagram, with the vacuum level at the top, a "higher"
work function is illustrated as further away from the vacuum level
in the downward direction. Thus, the definitions of HOMO and LUMO
energy levels follow a different convention than work
functions.
[0012] Layers, materials, regions, and devices may be described
herein in reference to the color of light they emit. In general, as
used herein, an emissive region that is described as producing a
specific color of light may include one or more emissive layers
disposed over each other in a stack.
[0013] As used herein, a "red" layer, material, region, or device
refers to one that emits light in the range of about 580-700 nm or
having a highest peak in its emission spectrum in that region.
Similarly, a "green" layer, material, region, or device refers to
one that emits or has an emission spectrum with a peak wavelength
in the range of about 500-600 nm; a "blue" layer, material, or
device refers to one that emits or has an emission spectrum with a
peak wavelength in the range of about 400-500 nm. In some
arrangements, separate regions, layers, materials, regions, or
devices may provide separate "deep blue" and a "light blue" light.
As used herein, in arrangements that provide separate "light blue"
and "deep blue", the "deep blue" component refers to one having a
peak emission wavelength that is at least about 4 nm less than the
peak emission wavelength of the "light blue" component. Typically,
a "light blue" component has a peak emission wavelength in the
range of about 465-500 nm, and a "deep blue" component has a peak
emission wavelength in the range of about 400-470 nm, though these
ranges may vary for some configurations. Similarly, a color
altering layer refers to a layer that converts or modifies another
color of light to light having a wavelength as specified for that
color. For example, a "red" color filter refers to a filter that
results in light having a wavelength in the range of about 580-700
nm. In general, there are two classes of color altering layers:
color filters that modify a spectrum by removing unwanted
wavelengths of light, and color changing layers that convert
photons of higher energy to lower energy. A component "of a color"
refers to a component that, when activated or used, produces or
otherwise emits light having a particular color as previously
described. For example, a "first emissive region of a first color"
and a "second emissive region of a second color different than the
first color" describes two emissive regions that, when activated
within a device, emit two different colors as previously
described.
[0014] As used herein, emissive materials, layers, and regions may
be distinguished from one another and from other structures based
upon light initially generated by the material, layer or region, as
opposed to light eventually emitted by the same or a different
structure. The initial light generation typically is the result of
an energy level change resulting in emission of a photon. For
example, an organic emissive material may initially generate blue
light, which may be converted by a color filter, quantum dot or
other structure to red or green light, such that a complete
emissive stack or sub-pixel emits the red or green light. In this
case the initial emissive material or layer may be referred to as a
"blue" component, even though the sub-pixel is a "red" or "green"
component.
[0015] In some cases, it may be preferable to describe the color of
a component such as an emissive region, sub-pixel, color altering
layer, or the like, in terms of 1931 CIE coordinates. For example,
a yellow emissive material may have multiple peak emission
wavelengths, one in or near an edge of the "green" region, and one
within or near an edge of the "red" region as previously described.
Accordingly, as used herein, each color term also corresponds to a
shape in the 1931 CIE coordinate color space. The shape in 1931 CIE
color space is constructed by following the locus between two color
points and any additional interior points. For example, interior
shape parameters for red, green, blue, and yellow may be defined as
shown below:
TABLE-US-00001 Color CIE Shape Parameters Central Red Locus:
[0.6270, 0.3725]; [0.7347, 0.2653]; Interior: [0.5086, 0.2657]
Central Green Locus: [0.0326, 0.3530]; [0.3731, 0.6245]; Interior:
[0.2268, 0.3321 Central Blue Locus: [0.1746, 0.0052]; [0.0326,
0.3530]; Interior: [0.2268, 0.3321] Central Yellow Locus: [0.3731,
0.6245]; [0.6270, 0.3725]; Interior: [0.3700, 0.4087]; [0.2886,
0.4572]
[0016] More details on OLEDs, and the definitions described above,
can be found in U.S. Pat. No. 7,279,704, which is incorporated
herein by reference in its entirety.
SUMMARY
[0017] According to an embodiment, an organic light emitting
diode/device (OLED) is also provided. The OLED can include an
anode, a cathode, and an organic layer, disposed between the anode
and the cathode. According to an embodiment, the organic light
emitting device is incorporated into one or more device selected
from a consumer product, an electronic component module, and/or a
lighting panel.
[0018] In an embodiment, a device is provided that includes a
full-color display panel having a plurality of pixels, each
comprising one or more sub-pixels, at least one of which includes a
green sub-pixel, a blue sub-pixel, and two red sub-pixels having
different emission spectra.
[0019] In an embodiment, a device is provided that includes a
full-color organic display panel comprising a plurality of pixels,
at least one of which includes a red sub-pixel having 1931 CIE
coordinates (Rx, Ry); and a green sub-pixel having 1931 CIE
coordinates (Gx, Gy); wherein the product
(0.75-Rx)(Ry-0.25)(Gy-0.5)(0.4-Gx) is at least than 1.5.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 shows an organic light emitting device.
[0021] FIG. 2 shows an inverted organic light emitting device that
does not have a separate electron transport layer.
[0022] FIGS. 3 and 4 show a plot and simulated results,
respectively, for a 10.4'' OLED display operating at 500 cd/m.sup.2
with color gamut as a percentage of Rec2020 versus power
consumption for a D65 white point and three common color systems.
Also shown are three additional data points with enhanced green
color saturation.
[0023] FIGS. 5A, 5B, and 5C show examples of sub-pixel layouts for
a four sub-pixel architecture as disclosed herein, for example
using a DCIP3 red and a Rec2020 Red combined with Rec2020 blue and
green to achieve Rec2020 image quality with close to DCIP3 power
consumption.
DETAILED DESCRIPTION
[0024] Generally, an OLED comprises at least one organic layer
disposed between and electrically connected to an anode and a
cathode. When a current is applied, the anode injects holes and the
cathode injects electrons into the organic layer(s). The injected
holes and electrons each migrate toward the oppositely charged
electrode. When an electron and hole localize on the same molecule,
an "exciton," which is a localized electron-hole pair having an
excited energy state, is formed. Light is emitted when the exciton
relaxes via a photoemissive mechanism. In some cases, the exciton
may be localized on an excimer or an exciplex. Non-radiative
mechanisms, such as thermal relaxation, may also occur, but are
generally considered undesirable.
[0025] The initial OLEDs used emissive molecules that emitted light
from their singlet states ("fluorescence") as disclosed, for
example, in U.S. Pat. No. 4,769,292, which is incorporated by
reference in its entirety. Fluorescent emission generally occurs in
a time frame of less than 10 nanoseconds.
[0026] More recently, OLEDs having emissive materials that emit
light from triplet states ("phosphorescence") have been
demonstrated. Baldo et al., "Highly Efficient Phosphorescent
Emission from Organic Electroluminescent Devices," Nature, vol.
395, 151-154, 1998; ("Baldo-I") and Baldo et al., "Very
high-efficiency green organic light-emitting devices based on
electrophosphorescence," Appl. Phys. Lett., vol. 75, No. 3, 4-6
(1999) ("Baldo-II"), are incorporated by reference in their
entireties. Phosphorescence is described in more detail in U.S.
Pat. No. 7,279,704 at cols. 5-6, which are incorporated by
reference.
[0027] FIG. 1 shows an organic light emitting device 100. The
figures are not necessarily drawn to scale. Device 100 may include
a substrate 110, an anode 115, a hole injection layer 120, a hole
transport layer 125, an electron blocking layer 130, an emissive
layer 135, a hole blocking layer 140, an electron transport layer
145, an electron injection layer 150, a protective layer 155, a
cathode 160, and a barrier layer 170. Cathode 160 is a compound
cathode having a first conductive layer 162 and a second conductive
layer 164. Device 100 may be fabricated by depositing the layers
described, in order. The properties and functions of these various
layers, as well as example materials, are described in more detail
in U.S. Pat. No. 7,279,704 at cols. 6-10, which are incorporated by
reference.
[0028] More examples for each of these layers are available. For
example, a flexible and transparent substrate-anode combination is
disclosed in U.S. Pat. No. 5,844,363, which is incorporated by
reference in its entirety. An example of a p-doped hole transport
layer is m-MTDATA doped with F.sub.4-TCNQ at a molar ratio of 50:1,
as disclosed in U.S. Patent Application Publication No.
2003/0230980, which is incorporated by reference in its entirety.
Examples of emissive and host materials are disclosed in U.S. Pat.
No. 6,303,238 to Thompson et al., which is incorporated by
reference in its entirety. An example of an n-doped electron
transport layer is BPhen doped with Li at a molar ratio of 1:1, as
disclosed in U.S. Patent Application Publication No. 2003/0230980,
which is incorporated by reference in its entirety. U.S. Pat. Nos.
5,703,436 and 5,707,745, which are incorporated by reference in
their entireties, disclose examples of cathodes including compound
cathodes having a thin layer of metal such as Mg:Ag with an
overlying transparent, electrically-conductive, sputter-deposited
ITO layer. The theory and use of blocking layers is described in
more detail in U.S. Pat. No. 6,097,147 and U.S. Patent Application
Publication No. 2003/0230980, which are incorporated by reference
in their entireties. Examples of injection layers are provided in
U.S. Patent Application Publication No. 2004/0174116, which is
incorporated by reference in its entirety. A description of
protective layers may be found in U.S. Patent Application
Publication No. 2004/0174116, which is incorporated by reference in
its entirety.
[0029] FIG. 2 shows an inverted OLED 200. The device includes a
substrate 210, a cathode 215, an emissive layer 220, a hole
transport layer 225, and an anode 230. Device 200 may be fabricated
by depositing the layers described, in order. Because the most
common OLED configuration has a cathode disposed over the anode,
and device 200 has cathode 215 disposed under anode 230, device 200
may be referred to as an "inverted" OLED. Materials similar to
those described with respect to device 100 may be used in the
corresponding layers of device 200. FIG. 2 provides one example of
how some layers may be omitted from the structure of device
100.
[0030] The simple layered structure illustrated in FIGS. 1 and 2 is
provided by way of non-limiting example, and it is understood that
embodiments of the invention may be used in connection with a wide
variety of other structures. The specific materials and structures
described are exemplary in nature, and other materials and
structures may be used. Functional OLEDs may be achieved by
combining the various layers described in different ways, or layers
may be omitted entirely, based on design, performance, and cost
factors. Other layers not specifically described may also be
included. Materials other than those specifically described may be
used. Although many of the examples provided herein describe
various layers as comprising a single material, it is understood
that combinations of materials, such as a mixture of host and
dopant, or more generally a mixture, may be used. Also, the layers
may have various sublayers. The names given to the various layers
herein are not intended to be strictly limiting. For example, in
device 200, hole transport layer 225 transports holes and injects
holes into emissive layer 220, and may be described as a hole
transport layer or a hole injection layer. In one embodiment, an
OLED may be described as having an "organic layer" disposed between
a cathode and an anode. This organic layer may comprise a single
layer, or may further comprise multiple layers of different organic
materials as described, for example, with respect to FIGS. 1 and
2.
[0031] Structures and materials not specifically described may also
be used, such as OLEDs comprised of polymeric materials (PLEDs)
such as disclosed in U.S. Pat. No. 5,247,190 to Friend et al.,
which is incorporated by reference in its entirety. By way of
further example, OLEDs having a single organic layer may be used.
OLEDs may be stacked, for example as described in U.S. Pat. No.
5,707,745 to Forrest et al, which is incorporated by reference in
its entirety. The OLED structure may deviate from the simple
layered structure illustrated in FIGS. 1 and 2. For example, the
substrate may include an angled reflective surface to improve
out-coupling, such as a mesa structure as described in U.S. Pat.
No. 6,091,195 to Forrest et al., and/or a pit structure as
described in U.S. Pat. No. 5,834,893 to Bulovic et al., which are
incorporated by reference in their entireties.
[0032] In some embodiments disclosed herein, emissive layers or
materials, such as emissive layer 135 and emissive layer 220 shown
in FIGS. 1-2, respectively, may include quantum dots. An "emissive
layer" or "emissive material" as disclosed herein may include an
organic emissive material and/or an emissive material that contains
quantum dots or equivalent structures, unless indicated to the
contrary explicitly or by context according to the understanding of
one of skill in the art. Such an emissive layer may include only a
quantum dot material which converts light emitted by a separate
emissive material or other emitter, or it may also include the
separate emissive material or other emitter, or it may emit light
itself directly from the application of an electric current.
Similarly, a color altering layer, color filter, upconversion, or
downconversion layer or structure may include a material containing
quantum dots, though such layer may not be considered an "emissive
layer" as disclosed herein. In general, an "emissive layer" or
material is one that emits an initial light, which may be altered
by another layer such as a color filter or other color altering
layer that does not itself emit an initial light within the device,
but may re-emit altered light of a different spectra content based
upon initial light emitted by the emissive layer.
[0033] Unless otherwise specified, any of the layers of the various
embodiments may be deposited by any suitable method. For the
organic layers, preferred methods include thermal evaporation,
ink-jet, such as described in U.S. Pat. Nos. 6,013,982 and
6,087,196, which are incorporated by reference in their entireties,
organic vapor phase deposition (OVPD), such as described in U.S.
Pat. No. 6,337,102 to Forrest et al., which is incorporated by
reference in its entirety, and deposition by organic vapor jet
printing (OVJP), such as described in U.S. Pat. No. 7,431,968,
which is incorporated by reference in its entirety. Other suitable
deposition methods include spin coating and other solution based
processes. Solution based processes are preferably carried out in
nitrogen or an inert atmosphere. For the other layers, preferred
methods include thermal evaporation. Preferred patterning methods
include deposition through a mask, cold welding such as described
in U.S. Pat. Nos. 6,294,398 and 6,468,819, which are incorporated
by reference in their entireties, and patterning associated with
some of the deposition methods such as ink jet and OVJD. Other
methods may also be used. The materials to be deposited may be
modified to make them compatible with a particular deposition
method. For example, substituents such as alkyl and aryl groups,
branched or unbranched, and preferably containing at least 3
carbons, may be used in small molecules to enhance their ability to
undergo solution processing. Substituents having 20 carbons or more
may be used, and 3-20 carbons is a preferred range. Materials with
asymmetric structures may have better solution processability than
those having symmetric structures, because asymmetric materials may
have a lower tendency to recrystallize. Dendrimer substituents may
be used to enhance the ability of small molecules to undergo
solution processing.
[0034] Devices fabricated in accordance with embodiments of the
present invention may further optionally comprise a barrier layer.
One purpose of the barrier layer is to protect the electrodes and
organic layers from damaging exposure to harmful species in the
environment including moisture, vapor and/or gases, etc. The
barrier layer may be deposited over, under or next to a substrate,
an electrode, or over any other parts of a device including an
edge. The barrier layer may comprise a single layer, or multiple
layers. The barrier layer may be formed by various known chemical
vapor deposition techniques and may include compositions having a
single phase as well as compositions having multiple phases. Any
suitable material or combination of materials may be used for the
barrier layer. The barrier layer may incorporate an inorganic or an
organic compound or both. The preferred barrier layer comprises a
mixture of a polymeric material and a non-polymeric material as
described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos.
PCT/US2007/023098 and PCT/US2009/042829, which are herein
incorporated by reference in their entireties. To be considered a
"mixture", the aforesaid polymeric and non-polymeric materials
comprising the barrier layer should be deposited under the same
reaction conditions and/or at the same time. The weight ratio of
polymeric to non-polymeric material may be in the range of 95:5 to
5:95. The polymeric material and the non-polymeric material may be
created from the same precursor material. In one example, the
mixture of a polymeric material and a non-polymeric material
consists essentially of polymeric silicon and inorganic
silicon.
[0035] In some embodiments, at least one of the anode, the cathode,
or a new layer disposed over the organic emissive layer functions
as an enhancement layer. The enhancement layer comprises a
plasmonic material exhibiting surface plasmon resonance that
non-radiatively couples to the emitter material and transfers
excited state energy from the emitter material to non-radiative
mode of surface plasmon polariton. The enhancement layer is
provided no more than a threshold distance away from the organic
emissive layer, wherein the emitter material has a total
non-radiative decay rate constant and a total radiative decay rate
constant due to the presence of the enhancement layer and the
threshold distance is where the total non-radiative decay rate
constant is equal to the total radiative decay rate constant. In
some embodiments, the OLED further comprises an outcoupling layer.
In some embodiments, the outcoupling layer is disposed over the
enhancement layer on the opposite side of the organic emissive
layer. In some embodiments, the outcoupling layer is disposed on
opposite side of the emissive layer from the enhancement layer but
still outcouples energy from the surface plasmon mode of the
enhancement layer. The outcoupling layer scatters the energy from
the surface plasmon polaritons. In some embodiments this energy is
scattered as photons to free space. In other embodiments, the
energy is scattered from the surface plasmon mode into other modes
of the device such as but not limited to the organic waveguide
mode, the substrate mode, or another waveguiding mode. If energy is
scattered to the non-free space mode of the OLED other outcoupling
schemes could be incorporated to extract that energy to free space.
In some embodiments, one or more intervening layer can be disposed
between the enhancement layer and the outcoupling layer. The
examples for intervening layer(s) can be dielectric materials,
including organic, inorganic, perovskites, oxides, and may include
stacks and/or mixtures of these materials.
[0036] The enhancement layer modifies the effective properties of
the medium in which the emitter material resides resulting in any
or all of the following: a decreased rate of emission, a
modification of emission line-shape, a change in emission intensity
with angle, a change in the stability of the emitter material, a
change in the efficiency of the OLED, and reduced efficiency
roll-off of the OLED device. Placement of the enhancement layer on
the cathode side, anode side, or on both sides results in OLED
devices which take advantage of any of the above-mentioned effects.
In addition to the specific functional layers mentioned herein and
illustrated in the various OLED examples shown in the figures, the
OLEDs according to the present disclosure may include any of the
other functional layers often found in OLEDs.
[0037] The enhancement layer can be comprised of plasmonic
materials, optically active metamaterials, or hyperbolic
metamaterials. As used herein, a plasmonic material is a material
in which the real part of the dielectric constant crosses zero in
the visible or ultraviolet region of the electromagnetic spectrum.
In some embodiments, the plasmonic material includes at least one
metal. In such embodiments the metal may include at least one of
Ag, Al, Au, Ir, Pt, Ni, Cu, W, Ta, Fe, Cr, Mg, Ga, Rh, Ti, Ru, Pd,
In, Bi, Ca alloys or mixtures of these materials, and stacks of
these materials. In general, a metamaterial is a medium composed of
different materials where the medium as a whole acts differently
than the sum of its material parts. In particular, we define
optically active metamaterials as materials which have both
negative permittivity and negative permeability. Hyperbolic
metamaterials, on the other hand, are anisotropic media in which
the permittivity or permeability are of different sign for
different spatial directions. Optically active metamaterials and
hyperbolic metamaterials are strictly distinguished from many other
photonic structures such as Distributed Bragg Reflectors ("DBRs")
in that the medium should appear uniform in the direction of
propagation on the length scale of the wavelength of light. Using
terminology that one skilled in the art can understand: the
dielectric constant of the metamaterials in the direction of
propagation can be described with the effective medium
approximation. Plasmonic materials and metamaterials provide
methods for controlling the propagation of light that can enhance
OLED performance in a number of ways.
[0038] In some embodiments, the enhancement layer is provided as a
planar layer. In other embodiments, the enhancement layer has
wavelength-sized features that are arranged periodically,
quasi-periodically, or randomly, or sub-wavelength-sized features
that are arranged periodically, quasi-periodically, or randomly. In
some embodiments, the wavelength-sized features and the
sub-wavelength-sized features have sharp edges.
[0039] In some embodiments, the outcoupling layer has
wavelength-sized features that are arranged periodically,
quasi-periodically, or randomly, or sub-wavelength-sized features
that are arranged periodically, quasi-periodically, or randomly. In
some embodiments, the outcoupling layer may be composed of a
plurality of nanoparticles and in other embodiments the outcoupling
layer is composed of a plurality of nanoparticles disposed over a
material. In these embodiments the outcoupling may be tunable by at
least one of varying a size of the plurality of nanoparticles,
varying a shape of the plurality of nanoparticles, changing a
material of the plurality of nanoparticles, adjusting a thickness
of the material, changing the refractive index of the material or
an additional layer disposed on the plurality of nanoparticles,
varying a thickness of the enhancement layer, and/or varying the
material of the enhancement layer. The plurality of nanoparticles
of the device may be formed from at least one of metal, dielectric
material, semiconductor materials, an alloy of metal, a mixture of
dielectric materials, a stack or layering of one or more materials,
and/or a core of one type of material and that is coated with a
shell of a different type of material. In some embodiments, the
outcoupling layer is composed of at least metal nanoparticles
wherein the metal is selected from the group consisting of Ag, Al,
Au, Ir, Pt, Ni, Cu, W, Ta, Fe, Cr, Mg, Ga, Rh, Ti, Ru, Pd, In, Bi,
Ca, alloys or mixtures of these materials, and stacks of these
materials. The plurality of nanoparticles may have additional layer
disposed over them. In some embodiments, the polarization of the
emission can be tuned using the outcoupling layer. Varying the
dimensionality and periodicity of the outcoupling layer can select
a type of polarization that is preferentially outcoupled to air. In
some embodiments the outcoupling layer also acts as an electrode of
the device.
[0040] It is believed that the internal quantum efficiency (IQE) of
fluorescent OLEDs can exceed the 25% spin statistics limit through
delayed fluorescence. As used herein, there are two types of
delayed fluorescence, i.e. P-type delayed fluorescence and E-type
delayed fluorescence. P-type delayed fluorescence is generated from
triplet-triplet annihilation (TTA).
[0041] On the other hand, E-type delayed fluorescence does not rely
on the collision of two triplets, but rather on the thermal
population between the triplet states and the singlet excited
states. Compounds that are capable of generating E-type delayed
fluorescence are required to have very small singlet-triplet gaps.
Thermal energy can activate the transition from the triplet state
back to the singlet state. This type of delayed fluorescence is
also known as thermally activated delayed fluorescence (TADF). A
distinctive feature of TADF is that the delayed component increases
as temperature rises due to the increased thermal energy. If the
reverse intersystem crossing rate is fast enough to minimize the
non-radiative decay from the triplet state, the fraction of back
populated singlet excited states can potentially reach 75%. The
total singlet fraction can be 100%, far exceeding the spin
statistics limit for electrically generated excitons.
[0042] E-type delayed fluorescence characteristics can be found in
an exciplex system or in a single compound. Without being bound by
theory, it is believed that E-type delayed fluorescence requires
the luminescent material to have a small singlet-triplet energy gap
(.DELTA.ES-T). Organic, non-metal containing, donor-acceptor
luminescent materials may be able to achieve this. The emission in
these materials is often characterized as a donor-acceptor
charge-transfer (CT) type emission. The spatial separation of the
HOMO and LUMO in these donor-acceptor type compounds often results
in small .DELTA.ES-T. These states may involve CT states. Often,
donor-acceptor luminescent materials are constructed by connecting
an electron donor moiety such as amino- or carbazole-derivatives
and an electron acceptor moiety such as N-containing six-membered
aromatic ring.
[0043] Devices fabricated in accordance with embodiments of the
invention can be incorporated into a wide variety of electronic
component modules (or units) that can be incorporated into a
variety of electronic products or intermediate components. Examples
of such electronic products or intermediate components include
display screens, lighting devices such as discrete light source
devices or lighting panels, etc. that can be utilized by the
end-user product manufacturers. Such electronic component modules
can optionally include the driving electronics and/or power
source(s). Devices fabricated in accordance with embodiments of the
invention can be incorporated into a wide variety of consumer
products that have one or more of the electronic component modules
(or units) incorporated therein. A consumer product comprising an
OLED that includes the compound of the present disclosure in the
organic layer in the OLED is disclosed. Such consumer products
would include any kind of products that include one or more light
source(s) and/or one or more of some type of visual displays. Some
examples of such consumer products include a flat panel display, a
curved display, a computer monitor, a medical monitor, a
television, a billboard, a light for interior or exterior
illumination and/or signaling, a heads-up display, a fully or
partially transparent display, a flexible display, a rollable
display, a foldable display, a stretchable display, a laser
printer, a telephone, a cell phone, tablet, a phablet, a personal
digital assistant (PDA), a wearable device, a laptop computer, a
digital camera, a camcorder, a viewfinder, a micro-display that is
less than 2 inches diagonal, a 3-D display, a virtual reality or
augmented reality display, a vehicle, a video walls comprising
multiple displays tiled together, a theater or stadium screen, and
a sign. Various control mechanisms may be used to control devices
fabricated in accordance with the present invention, including
passive matrix and active matrix. Many of the devices are intended
for use in a temperature range comfortable to humans, such as 18 C
to 30 C, and more preferably at room temperature (20-25 C), but
could be used outside this temperature range, for example, from -40
C to 80 C.
[0044] The materials and structures described herein may have
applications in devices other than OLEDs. For example, other
optoelectronic devices such as organic solar cells and organic
photodetectors may employ the materials and structures. More
generally, organic devices, such as organic transistors, may employ
the materials and structures.
[0045] In some embodiments, the OLED has one or more
characteristics selected from the group consisting of being
flexible, being rollable, being foldable, being stretchable, and
being curved. In some embodiments, the OLED is transparent or
semi-transparent. In some embodiments, the OLED further comprises a
layer comprising carbon nanotubes.
[0046] In some embodiments, the OLED further comprises a layer
comprising a delayed fluorescent emitter. In some embodiments, the
OLED comprises a RGB pixel arrangement or white plus color filter
pixel arrangement. In some embodiments, the OLED is a mobile
device, a hand held device, or a wearable device. In some
embodiments, the OLED is a display panel having less than 10 inch
diagonal or 50 square inch area. In some embodiments, the OLED is a
display panel having at least 10 inch diagonal or 50 square inch
area. In some embodiments, the OLED is a lighting panel.
[0047] In some embodiments of the emissive region, the emissive
region further comprises a host.
[0048] In some embodiments, the compound can be an emissive dopant.
In some embodiments, the compound can produce emissions via
phosphorescence, fluorescence, thermally activated delayed
fluorescence, i.e., TADF (also referred to as E-type delayed
fluorescence), triplet-triplet annihilation, or combinations of
these processes.
[0049] The OLED disclosed herein can be incorporated into one or
more of a consumer product, an electronic component module, and a
lighting panel. The organic layer can be an emissive layer and the
compound can be an emissive dopant in some embodiments, while the
compound can be a non-emissive dopant in other embodiments.
[0050] The organic layer can also include a host. In some
embodiments, two or more hosts are preferred. In some embodiments,
the hosts used maybe a) bipolar, b) electron transporting, c) hole
transporting or d) wide band gap materials that play little role in
charge transport. In some embodiments, the host can include a metal
complex. The host can be an inorganic compound.
Combination with Other Materials
[0051] The materials described herein as useful for a particular
layer in an organic light emitting device may be used in
combination with a wide variety of other materials present in the
device. For example, emissive dopants disclosed herein may be used
in conjunction with a wide variety of hosts, transport layers,
blocking layers, injection layers, electrodes and other layers that
may be present. The materials described or referred to below are
non-limiting examples of materials that may be useful in
combination with the compounds disclosed herein, and one of skill
in the art can readily consult the literature to identify other
materials that may be useful in combination.
[0052] Various materials may be used for the various emissive and
non-emissive layers and arrangements disclosed herein. Examples of
suitable materials are disclosed in U.S. Patent Application
Publication No. 2017/0229663, which is incorporated by reference in
its entirety.
Conductivity Dopants:
[0053] A charge transport layer can be doped with conductivity
dopants to substantially alter its density of charge carriers,
which will in turn alter its conductivity. The conductivity is
increased by generating charge carriers in the matrix material, and
depending on the type of dopant, a change in the Fermi level of the
semiconductor may also be achieved. Hole-transporting layer can be
doped by p-type conductivity dopants and n-type conductivity
dopants are used in the electron-transporting layer.
HIL/HTL:
[0054] A hole injecting/transporting material to be used in the
present invention is not particularly limited, and any compound may
be used as long as the compound is typically used as a hole
injecting/transporting material.
EBL:
[0055] An electron blocking layer (EBL) may be used to reduce the
number of electrons and/or excitons that leave the emissive layer.
The presence of such a blocking layer in a device may result in
substantially higher efficiencies, and or longer lifetime, as
compared to a similar device lacking a blocking layer. Also, a
blocking layer may be used to confine emission to a desired region
of an OLED. In some embodiments, the EBL material has a higher LUMO
(closer to the vacuum level) and/or higher triplet energy than the
emitter closest to the EBL interface. In some embodiments, the EBL
material has a higher LUMO (closer to the vacuum level) and or
higher triplet energy than one or more of the hosts closest to the
EBL interface. In one aspect, the compound used in EBL contains the
same molecule or the same functional groups used as one of the
hosts described below.
Host:
[0056] The light emitting layer of the organic EL device of the
present invention preferably contains at least a metal complex as
light emitting material, and may contain a host material using the
metal complex as a dopant material. Examples of the host material
are not particularly limited, and any metal complexes or organic
compounds may be used as long as the triplet energy of the host is
larger than that of the dopant. Any host material may be used with
any dopant so long as the triplet criteria is satisfied.
HBL:
[0057] A hole blocking layer (HBL) may be used to reduce the number
of holes and/or excitons that leave the emissive layer. The
presence of such a blocking layer in a device may result in
substantially higher efficiencies and/or longer lifetime as
compared to a similar device lacking a blocking layer. Also, a
blocking layer may be used to confine emission to a desired region
of an OLED. In some embodiments, the HBL material has a lower HOMO
(further from the vacuum level) and or higher triplet energy than
the emitter closest to the HBL interface. In some embodiments, the
HBL material has a lower HOMO (further from the vacuum level) and
or higher triplet energy than one or more of the hosts closest to
the HBL interface.
ETL:
[0058] An electron transport layer (ETL) may include a material
capable of transporting electrons. The electron transport layer may
be intrinsic (undoped), or doped. Doping may be used to enhance
conductivity. Examples of the ETL material are not particularly
limited, and any metal complexes or organic compounds may be used
as long as they are typically used to transport electrons.
Charge Generation Layer (CGL)
[0059] In tandem or stacked OLEDs, the CGL plays an essential role
in the performance, which is composed of an n-doped layer and a
p-doped layer for injection of electrons and holes, respectively.
Electrons and holes are supplied from the CGL and electrodes. The
consumed electrons and holes in the CGL are refilled by the
electrons and holes injected from the cathode and anode,
respectively; then, the bipolar currents reach a steady state
gradually. Typical CGL materials include n and p conductivity
dopants used in the transport layers.
[0060] Recent trends in display technology have seen large
improvements in the performance of the image quality of OLED
displays, particularly those used in mobile and portable devices
such as phones and laptops. Resolution has increased dramatically
as has size and color gamut--moving from standard RGB (sRGB) color
space to the Digital Cinema Initiatives P3 color space (DCI-P3,
DCI/P3, or DCIP3) color systems, with further advances to the ITU-R
Recommendation BT.2020 (Rec2020) color space being planned for 3 to
5 years from now. Most current mobile and TV displays have moved
from sRGB to the DCIP3 color system. The BT2020 system has a 56%
improvement in its ability to render colors compared to DCIP3 (and
190% improvement over sRGB) when plotted on 1931 CIE
coordinates.
[0061] However, increased display size, resolution and color gamut
all typically result in higher power consumption for the display
device. While great improvements in OLED materials, devices and
display driving have improved display efficiencies, the industry is
looking to further improve display visual appearance while
minimizing any associated increase in power consumption. Tables 1-3
below show the impact of blue, green, and red color saturation on
power consumption of a device, for a simulated 10.4'' OLED display
operating at 500 cd/m.sup.2.
TABLE-US-00002 TABLE 1 Different green and red color combinations
with both DCIP3 and Rec2020 blues Total Power (mW) RG Emitter
Combination DCIP3 Blue Rec2020 Blue DCIP3 green and red 1840 1776
Mid DCIP3/Rec2020 green and red 1953 1903 Rec2020 green and red
2199 2145
TABLE-US-00003 TABLE 2 Increasing green saturation with DCIP3 red
Total Power (mW) Green Emitter DCIP3 Blue Rec2020 Blue DCIP3 green
1840 1776 Mid DCIP3/Rec2020 green 1863 1816 Rec2020 green 1892
1843
TABLE-US-00004 TABLE 3 Increasing red saturation with DCIP3 green
Total Power (mW) Red Emitter DCIP3 Blue Rec2020 Blue DCIP3 red 1840
1776 Mid DCIP3/Rec2020 red 1901 1846 Rec2020 red 2024 1962
[0062] As shown in Table 1, increasing the blue color saturation
(from DCIP3 to Rec2020) results in approximately a 3% decrease in
power consumption. This is observed regardless of which combination
of green and red emitters is used (DCPI3 and/or Rec2020), as shown
by comparing the DCIP3 and Rec2020 blue columns in each row. Table
2 indicates that increasing green saturation from DCIP3 to Rec2020
results in a small increase in power consumption, about 3%.
Notably, as indicated in Table 3, increasing the red saturation
from DCIP3 to Rec2020 leads to a much larger increase in power
consumption of about 10%. For example, using a Rec2020 red emitter
with DCIP3 green and blue emitters results in a total power
consumption of 2024 mW, compared to a power consumption of 1840 mW
when the lower-saturation DCIP3 red is used with the same DCIP3
green and blue.
[0063] Embodiments disclosed herein provide novel devices,
arrangements, and techniques that may improve the color saturation
of OLED displays while avoiding or substantially reducing any
increase in power consumption that typically would be associated
with such increase in saturation, both with a three-subpixel per
pixel red/green/blue (RGB) architecture and a novel four sub-pixel
approach which uses two red sub-pixels for each pixel
(red/red/green/blue, or R1R2GB). Using a conventional
three-subpixel architecture, a partial Rec2020 gamut may be
achieved without a significant increase in power. This may be
accomplished, for example, by using a design rule that is based on
improving the color gamut of the display by increasing green
saturation more than red, thereby having little impact on power
consumption. Using a four-subpixel R1R2GB architecture as disclosed
herein, a Rec2020 gamut may be achieved with very little power
increase from current DCIP3 color gamut displays.
[0064] That is, embodiments disclosed herein provide techniques to
increase display color gamut while minimizing or avoiding any
associated increase in power consumption by using a conventional
side-by-side three sub-pixel RGB with a design rule that increases
green saturation more than red; and/or by using a novel four
sub-pixel R1R2GB architecture.
[0065] As described in further detail below, it has been found
that, for an OLED display, increasing the blue saturation from
DCIP3 to Rec2020 slightly decreases display power consumption,
increasing the green saturation from DCIP3 to Rec2020 slightly
increases display power consumption, while increasing the red
saturation from DCIP3 to Rec2020 more significantly increases
display power consumption.
[0066] Tables 4A-4C below (collectively "Table 4") show the results
of a series of simulations of different RGB emitters, showing their
1931 CIE, cd/A, proportion to make D65 white point, display power
consumption, percentage of Rec2020 color gamut achieved by the
specific combination of RGB emitters, and a new parameter, referred
to herein as the "saturation parameter" (sat parameter) for a
series of 10.4'' OLED displays operating at 500 cd/m.sup.2 and 50%
pixels fully illuminated with a 44% efficient circular
polarizer.
[0067] Run 1 in Table 4 represents a standard RGB (sRGB) color
system. Run 2 represents a DCIP3 system, and run 5 represents a
Rec2020 system.
[0068] The saturation parameter for a device is calculated by the
following product:
(0.75-Rx)*(Ry-0.25)*(Gy-0.5)*(0.4-Gx)
where the 1931 CIE coordinates of the green emitter are given by
(Gx, Gy) and for the red emitter by (Rx, Ry). Table 4 shows the
power consumption, color gamut (as a percentage of the Rec2020
gamut, "% Rec2020"), and the above-defined saturation parameter for
the various RGB emitter combinations. The cases where the
saturation parameter exceeds 1.5 are highlighted in Table 4 and
represent color combinations where the color saturation has been
increased with only a minimal increase in power consumption, by
increasing the green saturation more than or relative to the red
saturation.
[0069] As disclosed herein, it has been found that an OLED or
similar display may increase the provided color gamut while
minimizing the increase in display power consumption by selecting
sub-pixels such that the saturation parameter as defined above is
at least 1.5, i.e.,
(0.75-Rx)*(Ry-0.25)*(Gy-0.5)*(0.4-Gx)>1.5
This is the case because a saturation parameter of 1.5 or higher
represents a color gamut system in which the green is relatively
more saturated than the red. As shown by the data in Tables 1-4,
such an arrangement may provide an improved color gamut without the
associated increase in power consumption that would be expected for
conventional color gamut arrangements.
[0070] It has been found that devices that meet this requirement
can provide improved color gamut without the associated rise in
power consumption that would conventionally be required to achieve
the improved color gamut. Table 4 also show similar simulations and
combinations of red and green emitters for both DCIP3 and Rec2020
blue emitters. These results indicate that the DCIP3 blue leads to
approximately a 3% higher power consumption than the use of a
Rec2020 blue, for the same combination of red and green
emitters.
[0071] The results of the simulation results shown in Table 4 are
summarized in FIG. 3, which shows color saturation versus power
consumption for 3 color systems: sRGB, DCIP3 and Rec2020.
Increasing color saturation requires higher display power
consumption. FIG. 4 shows the raw data plotted in FIG. 3. Three
additional results are shown which refer to data points where the
saturation of the green emitter exceeds that of the red, based on
the DCIP3 and Rec2020 color gamuts--so a DCIP3 red and a green in
between DCIP3 and Rec2020, a red in between DCIP3 and Rec2020 and a
Rec2020 green and a DCIP3 red and a Rec2020 green. These correspond
to runs 7, 13, and 17 in Table 4 and FIG. 3 as noted (32, 31, and
33, respectively). In all three cases, the color saturation is
greatly increased without a significant increase in power
consumption relative to the cases for the three established color
systems. All three of the example devices provide enhanced green
saturation relative to red saturation than for the established
color gamuts.
[0072] Accordingly, it has been found that using red and green
sub-pixels in a device, where the saturation parameter of the
device is at least 1.5, improves the color gamut of the device
while minimizing or avoiding the increase in power consumption that
typically would be expected with a corresponding color gamut using
conventional arrangements. In some embodiments, a higher saturation
parameter threshold may be used, such as 1.6, 1.7, 1.8, 1.9, 2.0,
2.1, 2.2, 2.3, 2.4, 2.5, 3, 3.5, or more. In general, at higher
saturation parameter values, the green is relatively more saturated
than the red compared to conventional color gamut systems. The
saturation parameter typically is less than 1.5 in conventional
color gamut displays.
[0073] In a side-by-side or equivalent sub-pixel arrangement, each
red, green, or blue sub-pixel provides a corresponding RGB color
emission. Each sub-pixel may include one or more individual devices
to produce the associated color, such as the OLED devices described
with respect to FIGS. 1 and 2, microLED devices, quantum dot
devices, or combinations thereof. For example, one or more of the
sub-pixels in a full-color pixel within the display device may
include an OLED, a microLED, or a quantum dot device, any of which
may be unfiltered or filtered, or otherwise include one or more
color-altering components such as down-conversion layers, quantum
dots, color filters, microcavity structures, and the like. Any
suitable emissive material or materials may be used in each
device.
[0074] In some embodiments it may be preferred for the RGB color
emitted by a full-color pixel as disclosed herein to be at least as
saturated as the corresponding DCIP3 color gamut. Using the DCIP3
gamut as a threshold may ensure that a minimum acceptable gamut for
some applications is obtained, while still requiring less power or
a smaller increase in required power compared to conventional
techniques available to achieve a similar color gamut. For example,
comparing DCIP3 color gamut Run 2 with Run 7 in which the green
saturation is increased to Rec2020, only a 3 mW increase in power
consumption is observed for Run 7, but the color gamut increases
from 64% to 93% of the Rec2020 color gamut.
[0075] As previously disclosed and as shown in the results provided
in Table 4, embodiments disclosed herein may provide a substantial
portion of a desired color gamut such as the Rec2020 color gamut,
while still requiring less power to operate than conventional
devices. This may be achieved, for example, by selecting individual
sub-pixel structures to provide a saturation parameter of at least
1.5 or higher as previously disclosed. Specifically, embodiments
disclosed herein may operate with, i.e., provide a usable color
gamut equivalent to 95% of the Rec2020 1931 CIE color gamut while
operating at a power consumption of not more than 6.85 mW/cm.sup.2
(e.g., 2145 mW for a 313 cm.sup.2 panel) at a luminance of 500
nits; or 90% of the Rec2020 gamut at a power consumption of not
more than 5.78 mW/cm.sup.2 (e.g., 1840 mW, 313 cm.sup.2 panel) at
500 nits; or, more generally and synthesizing the results of Table
4, at least 80% or 90% of the Rec2020 1931 CIE color gamut, while
operating with a power consumption of not more than 5-6
mW/cm.sup.2.
[0076] From the prior disclosure and the experimental results shown
in Table 4, it can be seen that OLED display power consumption
increases with increasing color saturation as a result of
increasing the red subpixel color saturation, whereas increasing
both the blue and green color saturation generally does not
increase power consumption. To take advantage of this
understanding, some embodiments may use a novel four subpixel
display that includes a deep blue subpixel (B), a saturated green
subpixel (G), a saturated red subpixel (R2) and a less saturated
red pixel (R1), which may be referred to as a R1R2GB architecture.
Examples of layouts that use four sub-pixels are shown in FIGS.
5A-5C, though other arrangements may be used. Generally, each
arrangement will include sub-pixels arranged such that each pixel
includes one of each type, though in some embodiments a specific
sub-pixel structure may provide a sub-pixel for multiple pixels,
i.e., the sub-pixel may be "shared" among multiple pixels.
[0077] FIG. 5A shows a sub-pixel arrangement in which the four
sub-pixels are arranged in a 2.times.2 grid as shown, with the red
sub-pixels in opposite quadrants. FIG. 5B shows a linear
arrangement of four sub-pixels. FIG. 5C shows an arrangement in
which the central blue sub-pixel is shared between two adjacent
pixels 520, 530. Any of the pixel arrangements shown in FIGS. 5A-5C
may be repeated across a display panel, or portions of each
arrangement may be repeated such as where sub-pixel rendering
techniques are used, sub-pixels are shared between pixels, or the
like. Generally the R1 and R2 sub-pixels will have different
emission spectra, such that the R2 sub-pixel is more saturated than
the R1 sub-pixel. The specific arrangement of sub-pixels shown in
FIGS. 5A-5C is illustrative and other arrangements may be used. In
some cases, it may be desirable to minimize apparent dark areas
arising due to luminance content areas in each pixel by arranging
sub-pixels so that, for example, the R1 and R2 sub-pixels are
adjacent to one another. For example, the B and/or R2 sub-pixels
may have the least overall luminance content, especially since the
more saturated R2 sub-pixel typically will have a much lower "on
time" than the R1 sub-pixel.
[0078] Notably, arrangements disclosed herein may use only the four
sub-pixels in each pixel to achieve a high color gamut, whereas
other types of devices may use multiple sub-pixels of each type.
For example, other display architectures may use two of each
sub-pixel (two green, two blue, and two red) in order to achieve a
higher color gamut. Such arrangements may be less desirable than
the R1R2GB arrangements disclosed herein since they require more
complex circuitry and, in many cases, a higher total operating
power, especially in configurations which use multiple sub-pixels
of the same color to render a given color without consideration for
the specific color being rendered, the amount of power used by each
sub-pixel, and the like.
[0079] In contrast, embodiments disclosed herein recognize and
account for the fact that most images can be rendered using
non-saturated colors. Specifically, when using a R1R2GB sub-pixel
arrangement as disclosed herein, most images can be rendered using
only the green, blue, and R1 (less saturated) sub-pixels, thereby
resulting in a moderate power consumption with acceptable display
quality and color gamut. When highly saturated reds are required or
desired, the more saturated R2 pixel may be used. Such an
arrangement may be similar in approach, and may use similar driving
techniques, to RGB1B2 arrangements. Examples of RGB1B2 devices are
provided in U.S. Pat. Nos. 8,827,488, 8,902,245, 9,385,168,
10,304,906, and 10,700,134, the disclosure of each of which is
incorporated by reference.
[0080] Because the more saturated R2 subpixel may be used for only
a relatively small percentage of the time, the display may be able
to render a deeper red color but with the power consumption of a
lighter red on average, without using the specific combinations of
sub-pixel types previously described with respect to Table 4. So,
for example, if a Rec2020 emitter system (GBR2) is used in
conjunction with an additional DCIP3 red subpixel (R1), the
resulting display may achieve 100% of the Rec2020 color gamut with
a power consumption very close to a DCIP3 display. Using the base
Rec2020 and DCIP3 values from Table 4, for example, the resulting
device may use about 1840 mW as opposed to 2145 mW for a Rec2020
color gamut display, a power savings of nearly 15%. This approach
can be used for any desired color combinations. In some
embodiments, the more-saturated red sub-pixel also may be
relatively efficient, such that it causes a relatively small
increase in power relative to the less-saturated sub-pixel. For
example, the saturated R1 red sub-pixel may use not more than 10%
more power than the less-saturated R2 sub-pixel when used to
generate the same color in a pixel. That is, when a full-color
display using a four sub-pixel arrangement as disclosed herein is
used to display a given image, a pixel using the green, blue, and
more-saturated red sub-pixel may use not more than 10% or 5% more
power than when the same pixel uses the green, blue, and
less-saturated red sub-pixel to display the same image. This may
hold true even where the sub-pixels have relatively disparate CIE
coordinates, such as where the 1931 CIE x coordinates of the red
sub-pixels differ by at least 0.02, 0.04, or 0.06. Furthermore,
sub-pixel types may be selected based upon the data in Table 4 as
previously disclosed, but using a four sub-pixel arrangement such
as those shown in FIGS. 5A-5C, leading to additional improvements
in color gamut and/or power usage.
[0081] The "proximity" of the red sub-pixels on a color gamut chart
may vary depending upon the desired saturation and/or power
consumption. In some embodiments, the 1931 CIE x coordinate of the
two sub-pixels may vary by 0.02, 0.04, 0.06 or more. The more
saturated R2 sub-pixel may have an x coordinate of at least 0.69 or
0.70.
[0082] In some embodiments it may be desirable to strictly limit
use of the more saturated sub-pixel, and/or to limit the use of the
two red sub-pixels concurrently. For example, via circuitry,
programming logic, firmware, or combinations thereof, a four
sub-pixel device may be configured to only use one or the other of
the two red sub-pixels, such that both red sub-pixels are prevented
from being energized (i.e., operated to generate light)
concurrently some or all of the time. That is, the device may be
configured such that it never energizes both red sub-pixels at the
same time, or so that concurrent use of the two red sub-pixels is
limited to only specific situations such as where the display is
required to operate at very high luminances, such as for
readability in bright sunlight. This and other configurations allow
for devices that require no more than three data lines per pixel.
For example, a single data line may be used in conjunction with
other driving circuitry, programming logic, and/or firmware to
drive both red sub-pixels. An example of driving circuitry suitable
for use with a four sub-pixel, three data line arrangement is
provided in U.S. Pub. No. 2020/0312922, the disclosure of which is
incorporated by reference in its entirety.
[0083] The two red sub-pixels in embodiments disclosed herein may
be formed in any suitable manner. In some cases, the red sub-pixels
may include one or more common materials, which may be deposited
individually or in a single "blanket" deposition across both red
sub-pixel regions. In an embodiment, the red sub-pixels may include
emissive regions formed from a single deposition of one or more
common emissive materials, such that they share a common emissive
layer. Different emission spectra may be obtained via color
filters, conversion layers, cavity structures, or the like. For
example, two red sub-pixels may be patterned via OVJP or
shadow-masked vapor thermal evaporation (VTE), or made from the
same emitter using different cavity structures or cavity strengths
(or one with a cavity and the other without) to provide two
different red colors. As another example, in addition or
alternatively, a color filter could be used to make a deeper more
saturated red from a less saturated red emitter or from color
filters applied to a white emitting pixel. Alternatively, each red
sub-pixel may be formed separately, including two different OLED
depositions, which may use some or all of the same or different
emissive materials. As specific examples, the two R1 and R2
sub-pixels may include emissive regions that have different
emitters with the same or different hosts, or the same emissive
materials but at different doping concentrations, such as for
emissive materials in which a higher doping concentration will
result in more saturated emission.
[0084] In some embodiments, either or both of the red sub-pixels
may use a blue, light blue, or green emissive material in
combination with a color filter, conversion layer such as a quantum
dot down-conversion layer, cavity structures, or the like to
achieve a desired red emission spectrum. As another example, the
emissive stack in one or both red sub-pixels may be blue, light
blue or green/blue and quantum dot down conversion components may
be used to achieve the desired red emission spectra. For example,
two differently-patterned quantum dot layers may be used, one for
the more-saturated red sub-pixel and one for the less-saturated
sub-pixel. As another example, two quantum dot structures may be
mixed to provide both R1 and R2 colors, and then different cavities
structures may be used to select R1 or R2 in different
sub-pixels.
[0085] The various arrangements and sub-pixels disclosed herein may
use any suitable device structure, including OLEDs, microLEDs,
quantum dot devices, or combinations thereof. Four sub-pixel
arrangements may be particularly beneficial for microLED displays,
because red microLEDs typically have lower efficiencies than green
and blue microLEDs. OLED devices used in embodiments disclosed
herein may emit via fluorescence, phosphorescence, thermally
assisted delayed fluorescence (TADF), phosphor-sensitized TADF,
phosphor-sensitized fluorescence, or combinations thereof. The red
sub-pixels may use a common emissive material or structure or
different materials and/or structures, and one or both may use
cavity structures. Other structures used with OLEDs, microLEDs,
and/or quantum dot devices may be used, including color filters,
cavity structures, up- and/or down-conversion layers or components,
outcoupling components, and the like.
Simulation Data
[0086] Display simulations were performed using two techniques:
[0087] (1) Establishing different color simulated red, green and
blue emitters assuming gaussian optical emission spectra and
varying their external quantum efficiency (EQE), peak wavelength,
and FWHM spectra width. The output in Table 4 is provided in 1931
CIE coordinates and cd/A luminous efficacy.
[0088] (2) Use different RGB emitters to simulate OLED displays
with varying color gamuts--calculate RGB color balance to achieve
the D65 white point and then display power consumption based on RGB
efficiencies and color balance.
[0089] The DCIP3 blue was modeled as 459 nm, 55 nm FWHM peak with a
CIE of (0.141, 0.055). The Rec2020 blue was modeled as 467 nm peak,
10 nm FWHM with a CIE of (0.111, 0.047).
[0090] Devices were simulated using red, green, and blue sub-pixels
with the indicated properties. The simulated devices were 10.4''
OLED displays operating at 500 cd/m.sup.2 and 50% pixels fully
illuminated. The results are shown below in Tables 4A, 4B, and 4C,
which should be read as a single table with device types numbered
by "Run" across the three sub-tables. The results include the
simulated power consumption in mW versus color gamut, including the
examples shown in FIG. 3 as indicated by corresponding reference
numerals.
TABLE-US-00005 TABLE 4A Run Blue R CIE x R CIE y R cd/A G CIE x G
CIE y G cd/A D65 sRGB 1 P3 0.654 0.346 100.8 0.304 0.601 176.58
DCIP3 2 P3 0.682 0.318 73.1 0.253 0.706 201.47 sRGB red DCIP3 green
3 P3 0.654 0.346 100.8 0.253 0.706 201.47 sRGB green and DCIP3 red
4 P3 0.682 0.318 73.1 0.304 0.601 176.58 Rec2020 5 2020 0.708 0.292
50.5 0.167 0.794 205.50 DCIP3 green and Rec2020 red 6 2020 0.708
0.292 50.5 0.253 0.706 201.47 DCIP3 red and Rec2020 green (32) 7
2020 0.682 0.318 73.1 0.167 0.794 205.50 sRGB to DCIP3 sRGB red mid
green 8 P3 0.654 0.346 100.8 0.278 0.657 189.3 sRGB green and mid
red 9 P3 0.668 0.332 87.8 0.304 0.601 176.58 mid green and mid red
10 P3 0.668 0.332 87.8 0.278 0.657 189.3 mid green and DCIP3 red 11
P3 0.682 0.318 73.1 0.278 0.657 189.3 mid red and DCIP3 green 12 P3
0.668 0.332 87.8 0.253 0.706 201.47 DCIP3 to Rec2020 DCIP3 red mid
green (31) 13 2020 0.682 0.318 73.1 0.209 0.755 206 DCIP3 green and
mid red 14 2020 0.696 0.304 62.6 0.253 0.706 201.47 mid green and
mid red 15 2020 0.696 0.304 62.6 0.209 0.755 206 mid green and
Rec2020 red 16 2020 0.708 0.292 50.5 0.209 0.755 206 mid red and
Rec2020 green (33) 17 2020 0.696 0.304 62.6 0.167 0.794 205.50
DCIP3 to Rec2020 DCIP3 red mid green 18 P3 0.682 0.318 73.1 0.209
0.755 206 DCIP3 green and mid red 19 P3 0.696 0.304 62.6 0.253
0.706 201.47 mid green and mid red 20 P3 0.696 0.304 62.6 0.209
0.755 206 mid green and Rec2020 red 21 P3 0.708 0.292 50.5 0.209
0.755 206 mid red and Rec2020 green 22 P3 0.696 0.304 62.6 0.167
0.794 205.50 Rec2020 with P3 blue 23 P3 0.708 0.292 50.5 0.167
0.794 205.50 Rec2020 with P3 PHOLED blue 23 P P3 0.708 0.292 50.5
0.167 0.794 205.50 DCIP3 with Rec2020 blue 24 2020 0.682 0.318 73.1
0.253 0.706 201.47 DCIP3 red and Rec2020 green 25 P3 0.682 0.318
73.1 0.167 0.794 205.50 DCIP3 green and Rec2020 red 26 P3 0.708
0.292 50.5 0.253 0.706 201.47 sRGB red and Rec2020 green 27 P3
0.654 0.346 100.8 0.167 0.794 205.50
TABLE-US-00006 TABLE 4B Run R/W G/W B/W Power % Rec2020 D65 sRGB 1
23.5 69.9 6.6 1706 34.4% DCIP3 2 32.6 61.1 6.3 1840 63.9% sRGB red
DCIP3 green 3 38.4 55.3 6.3 1706 56.1% sRGB green and DCIP3 red 4
19.9 73.6 6.5 1778 42.1% Rec2020 5 44.40 51.50 4.10 2145 100.0%
DCIP3 green and Rec2020 red 6 28.5 66.2 5.3 1962 74.2% DCIP3 red
and Rec2020 green (32) 7 51.6 44.4 4.0 1843 93.3% sRGB to DCIP3
sRGB red mid green 8 31.4 62.1 6.5 1707 45.8% sRGB green and mid
red 9 21.6 71.8 6.6 1738 38.2% mid green and mid red 10 28.9 64.6
6.5 1750 49.6% mid green and DCIP3 red 11 26.6 66.9 6.5 1816 53.5%
mid red and DCIP3 green 12 35.4 58.3 6.3 1755 59.9% DCIP3 to
Rec2020 DCIP3 red mid green (31) 13 42.8 52.5 4.7 1816 81.0% DCIP3
green and mid red 14 30.6 64.1 5.3 1846 70.7% mid green and mid red
15 39.4 55.9 4.7 1903 84.7% mid green and Rec2020 red 16 36.8 58.5
4.7 2066 88.0% mid red and Rec2020 green (33) 17 47.6 48.36 4.06
1957 96.8% DCIP3 to Rec2020 DCIP3 red mid green 18 42.2 52.2 5.6
1863 77.5% DCIP3 green and mid red 19 30.1 63.6 6.3 1901 67.6% mid
green and mid red 20 38.95 55.43 5.62 1953 81.1% mid green and
Rec2020 red 21 36.31 58.05 5.64 2115 84.3% mid red and Rec2020
green 22 47.2 48 4.85 1994 92.8% Rec2020 with P3 blue 23 43.99
51.13 4.88 2199 95.9% Rec2020 with P3 PHOLED blue 23 P 43.99 51.13
4.88 1876 95.9% DCIP3 with Rec2020 blue 24 33.21 61.51 5.27 1776
66.8% DCIP3 red and Rec2020 green 25 51.1 44.08 4.82 1892 89.4%
DCIP3 green and Rec2020 red 26 28 65.68 6.32 2024 71.0% sRGB red
and Rec2020 green 27 59.91 35.35 4.73 1668 82.4%
TABLE-US-00007 TABLE 4C B CIE B CIE Saturation D65 Run x y
Parameter sRGB 1 0.141 0.055 0.89 DCIP3 2 0.141 0.055 1.39 sRGB red
DCIP3 green 3 0.141 0.055 2.77 sRGB green and DCIP3 red 4 0.141
0.055 0.45 Rec2020 5 0.131 0.047 1.21 DCIP3 green and Rec2020 red 6
0.131 0.047 0.53 DCIP3 red and Rec2020 green (32) 7 0.131 0.047
3.14 sRGB to DCIP3 sRGB red mid green 8 0.141 0.055 1.75 sRGB green
and mid red 9 0.141 0.055 0.65 mid green and mid red 10 0.141 0.055
1.29 mid green and DCIP3 red 11 0.141 0.055 0.88 mid red and DCIP3
green 12 0.141 0.055 2.03 DCIP3 to Rec2020 DCIP3 red mid green (31)
13 0.131 0.047 2.24 DCIP3 green and mid red 14 0.131 0.047 0.89 mid
green and mid red 15 0.131 0.047 1.43 mid green and Rec2020 red 16
0.131 0.047 0.86 mid red and Rec2020 green (33) 17 0.131 0.047 2.01
DCIP3 to Rec2020 DCIP3 red mid green 18 0.141 0.055 2.24 DCIP3
green and mid red 19 0.141 0.055 0.89 mid green and mid red 20
0.141 0.055 1.43 mid green and Rec2020 red 21 0.141 0.055 0.86 mid
red and Rec2020 green 22 0.141 0.055 2.01 Rec2020 with P3 blue 23
0.141 0.055 1.21 Rec2020 with P3 PHOLED blue 23 P 0.141 0.055 1.21
DCIP3 with Rec2020 blue 24 0.131 0.047 1.39 DCIP3 red and Rec2020
green 25 0.141 0.055 3.14 DCIP3 green and Rec2020 red 26 0.141
0.055 0.53 sRGB red and Rec2020 green 27 0.141 0.055 6.27
[0091] It is understood that the various embodiments described
herein are by way of example only, and are not intended to limit
the scope of the invention. For example, many of the materials and
structures described herein may be substituted with other materials
and structures without deviating from the spirit of the invention.
The present invention as claimed may therefore include variations
from the particular examples and preferred embodiments described
herein, as will be apparent to one of skill in the art. It is
understood that various theories as to why the invention works are
not intended to be limiting.
* * * * *