U.S. patent application number 15/066515 was filed with the patent office on 2016-09-15 for electroluminescent devices with improved optical out-coupling efficiencies.
The applicant listed for this patent is National Taiwan University. Invention is credited to Min Jiao, Wei-Kai Lee, Chun-Yu Lin, Hoang Yan Lin, Guo-Dong Su, Chung-Chih Wu.
Application Number | 20160268554 15/066515 |
Document ID | / |
Family ID | 56886827 |
Filed Date | 2016-09-15 |
United States Patent
Application |
20160268554 |
Kind Code |
A1 |
Wu; Chung-Chih ; et
al. |
September 15, 2016 |
ELECTROLUMINESCENT DEVICES WITH IMPROVED OPTICAL OUT-COUPLING
EFFICIENCIES
Abstract
An electroluminescent (EL) device is disclosed. An optically
reflective concave structure includes a first surface and a second
surface that lies at an angle relative to the first surface,
wherein at least the first and second surfaces are optically
reflective. One or more functional layers include a light emitting
layer, disposed over the surfaces of the optically reflective
concave structure, wherein at least one electroluminescent area of
the light emitting layer is defined on the first surface.
Especially, the ratio between the width of the first surface and
the thickness of the one or more functional layers in the optically
reflective concave structure is smaller than a constant value.
Inventors: |
Wu; Chung-Chih; (Taipei,
TW) ; Lin; Chun-Yu; (Taipei, TW) ; Lee;
Wei-Kai; (Taipei, TW) ; Jiao; Min; (Taipei,
TW) ; Lin; Hoang Yan; (Taipei, TW) ; Su;
Guo-Dong; (Taipei, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
National Taiwan University |
Taipei |
|
TW |
|
|
Family ID: |
56886827 |
Appl. No.: |
15/066515 |
Filed: |
March 10, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62177273 |
Mar 11, 2015 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 51/5268 20130101;
H01L 2251/558 20130101; H01L 33/60 20130101; H01L 27/32 20130101;
H01L 51/5271 20130101; H01L 27/3246 20130101 |
International
Class: |
H01L 51/52 20060101
H01L051/52; H01L 27/32 20060101 H01L027/32 |
Claims
1. An electroluminescent (EL) device, comprising: an optically
reflective concave structure, including a first surface, a second
surface that lies at an angle relative to the first surface, and a
third surface parallel to the first surface, wherein at least the
first and second surfaces of the optically reflective concave
structure are optically reflective; and one or more functional
layers including a light emitting layer, disposed over the surfaces
of the optically reflective concave structure, wherein at least one
electroluminescent area of the light emitting layer is defined on
the first surface of the optically reflective concave structure;
wherein the ratio between the maximum width of the first surface of
the optically reflective concave structure and the thickness of the
one or more functional layers in the optically reflective concave
structure is smaller than 200.
2. The electroluminescent device of claim 1, wherein the one or
more functional layers including a patterned interlayer formed
between the optically reflective concave structure and the other
functional layers, and the at least one electroluminescent area is
defined by the patterned interlayer.
3. The electroluminescent device of claim 1, further comprising a
bend of the one or more functional layers formed at the angle
between the first surface and the second surface, wherein the light
emitted from the electroluminescent area is re-directed and
out-coupled to air by the bend, when propagating in the one or more
functional layers.
4. The electroluminescent device of claim 1, further comprising: a
first portion of the one or more functional layers, disposed over
the first surface; and a second portion of the one or more
functional layers, disposed over the second surface, wherein the
light emitted from the electroluminescent area is re-directed and
out-coupled to air by the variation of the thicknesses between the
first portion and the second portion of the one or more functional
layers, when propagating from the first portion to the second
portion in the one or more functional layers.
5. The electroluminescent device of claim 1, further comprising an
index-matching material that is mostly filled on the first and
second surfaces of the optically reflective concave structure and
over the one or more functional layers.
6. The electroluminescent device of claim 5, wherein the ratio
between the maximum width of the first surface of the optically
reflective concave structure and the total thickness of the one or
more functional layers and the index-matching material in the
optically reflective concave structure is smaller than 60.
7. The electroluminescent device of claim 5, wherein the light
emitted from the electroluminescent area is re-directed and
out-coupled to air, and the number of reflection of the reflected
or total internal reflected light and corresponding optical loss is
reduced before being re-directed and out-coupled, when propagating
in the one or more functional layers and the index-matching
material.
8. The electroluminescent device of claim 5, wherein the refractive
indices of the other functional layers and the index-matching
material within the optically reflective concave structure are kept
within .+-.0.2 of that of the light emitting layer or higher than
that of the light emitting layer, and the other functional layers
and the index-matching material within the optically reflective
concave structure have relatively high transparency of more than
75% in the wavelength range of the light emitted from the
electroluminescent area.
9. The electroluminescent device of claim 5, wherein the exposed
surface of the index-matching material within the optically
reflective concave structure is flat or curved.
10. The electroluminescent device of claim 1, wherein the optically
reflective concave structure is directly formed by an optically
reflective material, the optically reflective material is selected
from the group consisting of metal and scattering reflector.
11. The electroluminescent device of claim 1, wherein the optically
reflective concave structure is composed of a concave structure and
an optically reflective surface, the material of the optically
reflective surface is selected from the group consisting of metal,
transparent conductive metal-oxide, transparent dielectric,
scattering reflector, distributed Bragg reflector formed by
alternate stacking of high-index/low-index materials, their
stacking and their combinations.
12. The electroluminescent device of claim 1, wherein the material
of the first surface is the same as that of the second surface of
the optically reflective concave structure.
13. The electroluminescent device of claim 1, wherein the material
of the first surface is different from that of the second surface
of the optically reflective concave structure.
14. The electroluminescent device of claim 1, wherein the
electroluminescent area of the light emitting layer is extended to
the intersection of the second and third surfaces of the optically
reflective concave structure.
15. The electroluminescent device of claim 1, wherein the optically
reflective surfaces of the optically reflective concave structure
have a relatively high optical reflectance more than 80% in the
wavelength range of the light emitted from the electroluminescent
area.
16. The electroluminescent device of claim 1, wherein the
functional layers in the optically reflective concave structure
have a relatively high transparency more than 75% in the wavelength
range of the light emitted from the electroluminescent area.
17. A display including said electroluminescent (EL) device of
claim 1, wherein the display comprising: a substrate; a thin-film
transistor formed on the substrate; and an interconnection
conductor, being electrical contact to the thin-film transistor,
wherein said electroluminescent device electrically contacts to the
interconnection conductor via the first surface of the optically
reflective concave structure.
18. The display of claim 17, wherein the interconnection conductor
also serves as the first surface of the optically reflective
concave structure in said electroluminescent device.
19. The display of claim 17, wherein the surfaces of the optically
reflective concave structure in said electroluminescent device is
non-conductive, and the one or more functional layers include a
first electrode disposed between the other functional layers and
the optically reflective concave structure, wherein the first
electrode is electrically connected to the interconnection
conductor and the one or more functional layers.
20. A display including said electroluminescent (EL) device of
claim 1, wherein the display comprising: a substrate; a thin-film
transistor formed on the substrate; and an interconnection
conductor, being electrical contact to the thin-film transistor,
wherein said electroluminescent device electrically contacts to the
interconnection conductor via the third surface of the optically
reflective concave structure.
21. The display of claim 20, wherein the interconnection conductor
also serves as the surfaces of the optically reflective concave
structure.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to and the benefit of U.S.
Provisional Patent Application Ser. No. 62/177,273, filed on Mar.
11, 2015, and entitled "Organic Light-Emitting Device Structures
with Improved Optical Out-Coupling and Their Applications", the
disclosure of which is incorporated by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention pertains to an electroluminescent (EL)
device, and more particularly pertains to an organic light-emitting
device (OLED) structures with improved optical out-coupling and
their applications.
BACKGROUND OF THE INVENTION
[0003] Due to various merits of organic light-emitting devices
(OLEDs), such as high efficiency, wide viewing angles, fast
response, potentially low cost etc., OLED technologies have become
an important next-generation display technology since Dr. Tang and
VanSlyke reported the first efficient and practical OLED in 1987.
Due to increasing efficiencies, the OLED is also becoming practical
for lighting applications. No matter display or lighting
applications, external quantum efficiencies (EQEs) of OLEDs are
essential. EQEs of OLEDs are determined by internal quantum
efficiencies (IQEs) and the optical out-coupling efficiencies.
Through appropriate combinations of materials for electrodes,
carrier-transport layers (e.g., hole-transport layers-HTL,
electron-transport layers-ETL), emission layers (EML), and their
stacking, internal quantum efficiencies can reach nearly 100%.
However, in typical OLED structures, optical out-coupling
efficiencies of OLEDs are still limited.
[0004] Currently typical OLEDs are fabricated on a substrate.
According to the direction of the light emission relative to the
substrate, OLEDs can be classified into bottom-emitting OLEDs or
top-emitting OLEDs. Bottom-emitting OLEDs 1 emit through the
transparent or semi-transparent substrate 10 as FIG. 1, while
top-emitting OLEDs 2 emit opposite the substrate direction as FIG.
2.
[0005] Please refer to FIG. 1, the bottom-emitting OLEDs 1 are
typically composed of a single or multiple organic material layers
12 stacking and sandwiched between top reflective electrode 13 and
bottom (semi-)transparent electrode 11. Through appropriate
combinations of materials for electrodes, carrier-transport layers
(e.g., hole-transport layers-HTL, electron-transport layers-ETL),
emission layers (EML), and their stacking, internal quantum
efficiencies can reach nearly 100%. However, in typical
bottom-emitting OLED 1 structures, for example, glass or plastic
substrate/transparent electrode such as ITO/organic
layers/reflective electrode such as Al, due to higher refractive
indices n of the organic layers (typically n.gtoreq.1.7) and
transparent electrodes (typically n.gtoreq.1.8) than those of
substrates (e.g., n.about.1.4-1.5 for glass substrates), a
significant portion of internally generated light with larger
angles will be confined in the device by total internal reflection
at the electrode-substrate interface and cannot enter the substrate
for out-coupling into air. For the light entering the substrate 10,
due to higher refractive indices of transparent substrates (e.g.,
n.about.1.4-1.5 for glass substrates) than that of air, again a
significant portion of light with larger angles will be confined in
the substrate by total internal reflection at the substrate-air
interface and cannot be out-coupled into air. As such, in typical
bottom-emitting OLED structures, optical out-coupling efficiencies
are generally limited to only 20-25%.
[0006] On the other hand, the typical top-emitting OLEDs 2 have the
structure of substrate 20 such as glass or plastic/bottom
reflective electrode such as metal 21/organic layer(s) 22/top
(semi-)transparent electrode 23 such as ITO, thin metal, as shown
in FIG. 2. In some cases, the top (semi-)transparent electrode may
be further over-coated with transparent passivation or capping
layer. Due to higher refractive indices of organic layers
(typically n.gtoreq.1.7), transparent electrodes (typically
n.gtoreq.1.8), and even transparent passivation or capping layers
than that of air, a significant portion of internally generated
light with larger angles will be confined in the device by total
internal reflection at the device-air interface and cannot be
out-coupled to air as shown in FIG. 2. Therefore, in typical
top-emitting OLED structures, optical out-coupling efficiencies are
generally also limited.
[0007] Therefore, to achieve high-efficiency, power-saving OLED
displays or lighting, the optical out-coupling efficiencies have to
be effectively raised by out-coupling otherwise trapped OLED
internal light. This invention thus aims to provide OLED device
structures that can effectively enhance optical out-coupling
efficiencies of OLEDs.
SUMMARY OF THE PRESENT INVENTION
[0008] In order to overcome the drawbacks of prior arts, the
present invention provides various embodiments described below.
[0009] In certain embodiments, an electroluminescent (EL) device is
disclosed, comprising a substrate, an optically reflective concave
structure and one or more functional layers. The optically
reflective concave structure includes a first surface, a second
surface that lies at an angle relative to the first surface, and a
third surface parallel to the first surface, wherein at least the
first and second surfaces of the optically reflective concave
structure are optically reflective. The one or more functional
layers include a light emitting layer, disposed over the surfaces
of the optically reflective concave structure, wherein at least one
electroluminescent area of the light emitting layer is defined on
the first surface of the optically reflective concave structure.
The one or more functional layers further include a patterned
interlayer formed between the optically reflective concave
structure and the other functional layers, and the at least one
electroluminescent area is defined by the patterned interlayer.
Especially, a first ratio between the maximum width of the first
surface of the optically reflective concave structure and the
thickness of the one or more functional layers in the optically
reflective concave structure is smaller than a first constant
value, which is 200, 180, 150, 100, 80 or 50. In an preferred
embodiments, the electroluminescent device with the optical
out-coupling efficiencies is disclosed when the first ratio is
smaller than 50.
[0010] In certain embodiments, the electroluminescent device
further comprises a bend of the one or more functional layers
formed at the angle between the first surface and the second
surface, wherein the light emitted from the electroluminescent area
is re-directed and out-coupled to air by the bend, when propagating
in the one or more functional layers.
[0011] In certain embodiments, the electroluminescent device
further comprises a first portion of the one or more functional
layers, disposed over the first surface; and a second portion of
the one or more functional layers, disposed over the second
surface, wherein the light emitted from the electroluminescent area
is re-directed and out-coupled to air by the variation of the
thicknesses between the first portion and the second portion of the
one or more functional layers, when propagating from the first
portion to the second portion in the one or more functional
layers.
[0012] In certain embodiments, the optically reflective concave
structure is directly formed by an optically reflective material,
selected from the group consisting of metal and scattering
reflector. In certain embodiments, the optically reflective concave
structure is composed of a concave structure and an optically
reflective surface, and the material of the optically reflective
surface is selected from the group consisting of metal, transparent
conductive metal-oxide, transparent dielectric, scattering
reflector, distributed Bragg reflector formed by alternate stacking
of high-index/low-index materials, and their stacking or
combinations. The material of the first surface is the same as, or
different from that of the second surface of the concave
structure.
[0013] In certain embodiments, the electroluminescent area of the
light emitting layer is extended to the intersection of the second
and third surfaces of the optically reflective concave
structure.
[0014] In certain embodiments, the optically reflective surfaces of
the optically reflective concave structure have a relatively high
optical reflectance more than 80% in the wavelength range of the
light emitted from the electroluminescent area.
[0015] In certain embodiments, the functional layers in the
optically reflective concave structure have a relatively high
transparency more than 75% in the wavelength range of the light
emitted from the electroluminescent area.
[0016] In certain embodiments, another electroluminescent (EL)
device is disclosed. Said electroluminescent (EL) device further
comprising an index-matching material that is mostly filled on the
first and second surfaces of the optically reflective concave
structure and over the one or more functional layers. The light
emitted from the electroluminescent area is re-directed and
out-coupled to air, and the number of reflection of the reflected
or total internal reflected light and corresponding optical loss is
reduced before being re-directed and out-coupled, when propagating
in the one or more functional layers and the index-matching
material. Especially, a second ratio between the maximum width of
the first surface of the optically reflective concave structure and
the total thickness of the one or more functional layers and the
index-matching material in the optically reflective concave
structure is smaller than a second constant value, which is 60 or
30. In an preferred embodiments, the electroluminescent device with
the optical out-coupling efficiencies is disclosed when the second
ratio is smaller than 30.
[0017] In certain embodiments, the refractive indices of the other
functional layers and the index-matching material within the
optically reflective concave structure are kept within .+-.0.2 of
that of the light emitting layer or higher than that of the light
emitting layer, and the other functional layers and the
index-matching material within the optically reflective concave
structure have relatively high transparency of more than 75% in the
wavelength range of the light emitted from the electroluminescent
area.
[0018] In certain embodiments, the exposed surface of the
index-matching material within the optically reflective concave
structure is flat or curved.
[0019] In certain embodiments, a display including said
electroluminescent (EL) device is disclosed. The display comprises
a substrate, a thin-film transistor (TFT) formed on the substrate,
and an interconnection conductor being electrical contact to the
thin-film transistor, wherein said electroluminescent device
electrically contacts to the interconnection conductor via the
first surface of the optically reflective concave structure.
[0020] In certain embodiments, the interconnection conductor also
serves as the first surface of the optically reflective concave
structure in said electroluminescent device.
[0021] In certain embodiments, the surfaces of the optically
reflective concave structure in said electroluminescent device is
non-conductive, and the one or more functional layers include a
first electrode disposed between the other functional layers and
the optically reflective concave structure, wherein the first
electrode is electrically connected to the interconnection
conductor and the one or more functional layers.
[0022] In certain embodiments, a display including said
electroluminescent (EL) device is disclosed. The display comprises
a substrate, a thin-film transistor (TFT) formed on the substrate,
and an interconnection conductor being electrical contact to the
thin-film transistor, wherein said electroluminescent device
electrically contacts to the interconnection conductor via the
third surface of the optically reflective concave structure.
[0023] In certain embodiments, the interconnection conductor also
serves as the surfaces of the optically reflective concave
structure.
[0024] The above description is only an outline of the technical
schemes of the present invention. Preferred embodiments of the
present invention are provided below in conjunction with the
attached drawings to enable one with ordinary skill in the art to
better understand said and other objectives, features and
advantages of the present invention and to make the present
invention accordingly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1. Schematic structure of typical bottom-emitting
OLED.
[0026] FIG. 2. Schematic structure of typical top-emitting
OLED.
[0027] FIG. 3. The top-emitting OLED structure contains a single
emission zone inside the concave and optically reflective structure
formed on a substrate.
[0028] FIG. 4. The top-emitting OLED structure contains multiple
emission zones inside the concave and optically reflective
structure formed on a substrate.
[0029] FIG. 5. The top-emitting OLED structure contains a single
emission zone extending to the side slopes and the top edge of the
concave and optically reflective structure formed on a
substrate.
[0030] FIG. 6. The top-emitting OLED structure contains multiple
emission zones extending to the side slopes and the top edge of the
concave and optically reflective structure formed on a
substrate.
[0031] FIG. 7a. The optical energy originally trapped by total
internal reflection or reflection at the OLED functional material
layer(s)/air interface may be re-directed and be out-coupled to air
by the bending of the concave structure, when propagating in the
layers.
[0032] FIG. 7b. The optical energy originally trapped by total
internal reflection or reflection at the OLED functional material
layer(s)/air interface may be re-directed and be out-coupled to air
by the change/variation of the layer thicknesses, when propagating
in the layers.
[0033] FIGS. 8a and 8b. The top-emitting OLED structure having a
single emission zone inside the concave (at the bottom) and
optically reflective structure formed on a substrate and further
having an index-matching filling material disposed inside the
concave area. The top surface of the index-matching filling
material/layer is flat or curved/non-planar.
[0034] FIGS. 9a and 9b. The top-emitting OLED structure having
multiple emission zones inside the concave (at the bottom) and
optically reflective structure formed on a substrate and further
having an index-matching filling material disposed inside the
concave area. The top surface of the index-matching filling
material/layer is flat or curved/non-planar.
[0035] FIGS. 10a and 10b. The top-emitting OLED structure having a
single emission zone a single emission zone extending to the side
slopes and the top edge of the concave and optically reflective
structure formed on a substrate and further having an
index-matching filling material disposed inside the concave area.
The top surface of the index-matching filling material/layer is
flat or curved/non-planar.
[0036] FIGS. 11a and 11b. The top-emitting OLED structure having a
single emission zone a single emission zone extending to the side
slopes and the top edge of the concave and optically reflective
structure formed on a substrate and further having an
index-matching filling material disposed inside the concave area.
The top surface of the index-matching filling material/layer is
flat or curved/non-planar.
[0037] FIGS. 12a, 12b and 12c. Several possible types of the
concave and optically reflective structures of this invention.
[0038] FIGS. 13a, 13b and 13c. Several possible embodiments of
top-emitting OLEDs having the concave and optically reflective
structure.
[0039] FIG. 14. One possible fabrication/processing flow for
fabrication of FIG. 13a.
[0040] FIG. 15. Using the etching method to form concave areas in
the concave structure layer.
[0041] FIG. 16. Using the photo-patterning/developing of a
photopolymer to form the concave areas in the concave structure
layer.
[0042] FIGS. 17a, 17b and 17c. Several other possible embodiments
of top-emitting OLEDs having the concave and optically reflective
structure.
[0043] FIGS. 18a, 18b and 18c. Several other possible embodiments
of top-emitting OLEDs having the concave and optically reflective
structure.
[0044] FIG. 19. The schematic integration structure for the pixel
of a current and typical top-emitting AMOLED.
[0045] FIGS. 20a, 20b and 20c. Several possible embodiments of
top-emitting AMOLEDs having the concave and optically reflective
structure for the pixel OLED.
[0046] FIGS. 21a, 21b and 21c. Several possible embodiments of
top-emitting AMOLEDs having the concave and optically reflective
structure for the pixel OLED with the flat surface of the
index-matching filling material/layer.
[0047] FIGS. 22a, 22b and 22c. Several possible embodiments of
top-emitting AMOLEDs having the concave and optically reflective
structure for the pixel OLED with the curved/non-flat surface of
the index-matching filling material/layer.
[0048] FIGS. 23a, 23b and 23c. Various top-emitting AMOLEDs having
the concave and optically reflective structure and having the
bottom reflective electrode (and also the optically reflective
coating over the concave area) of the pixel OLED also serve as the
interconnection conductor with the driving TFT below.
[0049] FIGS. 24a, 24b and 24c. Various top-emitting AMOLEDs having
the concave and optically reflective structure and having the
bottom reflective electrode (and also the optically reflective
coating over the concave area) of the pixel OLED also serve as the
interconnection conductor with the driving TFT below and the top
surface of the index-matching filling material/layer is flat.
[0050] FIGS. 25a, 25b and 25c. Various top-emitting AMOLEDs having
the concave and optically reflective structure and having the
bottom reflective electrode (and also the optically reflective
coating over the concave area) of the pixel OLED also serve as the
interconnection conductor with the driving TFT below and the top
surface of the index-matching filling material/layer is
curved/non-flat.
[0051] FIGS. 26a, 26b and 26c. Several more possible concave and
optically reflective structures that combine different reflective
material layers.
[0052] FIGS. 27a and 27b. Possible embodiments of top-emitting
OLEDs having the concave and optically reflective structure based
on FIG. 26a.
[0053] FIGS. 28a and 28b. Possible embodiments of top-emitting
OLEDs having the concave and optically reflective structure based
on FIG. 26a and the top surface of the index-matching filling
material/layer is flat.
[0054] FIGS. 29a and 29b. Possible embodiments of top-emitting
OLEDs having the concave and optically reflective structure based
on FIG. 26a and the top surface of the index-matching filling
material/layer is curved/non-flat.
[0055] FIGS. 30a and 30b. Several possible embodiments of
top-emitting AMOLEDs having the concave and optically reflective
structure for the pixel OLED, based on the structures of FIGS.
27a-27b.
[0056] FIGS. 31a and 31b. Several possible embodiments of
top-emitting AMOLEDs having the concave and optically reflective
structure for the pixel OLED, based on the structures of FIG.
27a-27b, and the top surface of the index-matching filling
material/layer is flat.
[0057] FIGS. 32a and 32b. Several possible embodiments of
top-emitting AMOLEDs having the concave and optically reflective
structure for the pixel OLED, based on the structures of FIG.
27a-27b, and the top surface of the index-matching filling
material/layer is curved/non-flat.
DETAILED DESCRIPTION OF THE INVENTION
[0058] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory only and are not restrictive of the invention, as
claimed. It should be noted that, as used in the specification and
the appended claims, the singular forms "a", an and the include
plural referents unless the context clearly dictates otherwise.
Thus, for example, reference to "a material" may include mixtures
of materials; reference to "a display" may include multiple
displays, and the like. References cited herein are hereby
incorporated by reference in their entirety, except to the extent
that they conflict with teachings explicitly set forth in this
specification.
[0059] Please refer to FIG. 3 to FIG. 7, the invention provides an
OLED structure with high optical out-coupling efficiency, whose
principles, structure and characteristics are described as
following (1)-(6).
[0060] (1) First, the OLED structure contains an optically
reflective concave structure 200 formed on a substrate 100. The
optically reflective concave structure 200 includes a first surface
(a bottom surface), a second surface (an inclined surface) that
lies at an angle relative to the first surface, and a third surface
(a top surface) parallel to the first surface, and at least the
first and second surfaces of the optically reflective concave
structure 200 are optically reflective.
[0061] (2) Second, various functional layers 300 of the OLED, such
as at least one light emitting layer (or called emission layer),
charge transport layer(s), electrode layer(s), insulating
dielectric layer(s) to define the electroluminescent area
305/305a/305b/305c (or called emission zones) of the OLED, and
passivation/capping layer(s) etc. that typically have refractive
indices higher than that of air, are disposed over the surfaces of
the optically reflective concave structure 200, forming one or
multiple OLED electroluminescent areas 305/305a on the bottom of
the concave structure, as shown in FIG. 3 and FIG. 4, or forming
one or multiple OLED electroluminescent areas 305b/305c that extend
to the top edge of the concave structure 200, as shown in FIG. 5
and FIG. 6.
[0062] (3) With such an OLED structure, the optical energy
originally trapped by total internal reflection or reflection at
the OLED functional material layer(s)/air interface may be
re-directed and be out-coupled to air by the bending of the concave
structure, as shown in FIG. 7a, or the change/variation of the
layer thicknesses, as shown in FIG. 7b, when light L is propagating
in the layers 300. Wherein the bend of the one or more functional
layers formed at the angle between the first surface and the second
surface. The thickness of a first portion of the one or more
functional layers 300 disposed over the first surface is d, and the
thickness of a second portion of the one or more functional layers
300 disposed over the second surface is <d.
[0063] (4) To reduce the optical loss of reflected or total
internal reflected light during reflection/propagation in the
structure, the concave structure should have a relatively high
optical reflectance (e.g., >80%) in the wavelength range of the
light emitted from the electroluminescent area (or called emission
wavelength range).
[0064] (5) To reduce the optical loss of reflected or total
internal reflected light during reflection/propagation in the
structure, various functional layers in the concave structure
should have a relatively high transparency (e.g., >75%) in the
emission wavelength range.
[0065] (6) To reduce the optical loss of reflected or total
internal reflected light during reflection/propagation in the
structure, the ratio between the maximum width of the concave area
and the total thickness of functional layers in the concave and
optical reflective structure should be kept small enough to reduce
the number of reflection and total internal reflection within the
structure. For example, the ratio of maximum width overall the
total layer thickness is <200, 180, 150, 100, 80 or 50. In an
preferred embodiments, the electroluminescent device with the
optical out-coupling efficiencies is disclosed when the ratio is
<50.
[0066] Please refer to FIG. 8 to FIG. 11, this invention provides
another OLED structure with high optical out-coupling efficiency,
whose principles, structure and characteristics are described as
following (1)-(10).
[0067] (1) First, the OLED structure contains an optically
reflective concave structure 200 formed on a substrate 100. The
optically reflective concave structure 200 includes a first
surface, a second surface that lies at an angle relative to the
first surface, and a third surface parallel to the first surface,
and at least the first and second surfaces of the optically
reflective concave structure 200 are optically reflective.
[0068] (2) Second, various functional layers 300 of the OLED, such
as emission layer(s), charge transport layer(s), electrode
layer(s), insulating dielectric layer(s) to define the emission
area 305/305a/305b/305c of the OLED, and passivation/capping
layer(s) etc. that typically have refractive indices higher than
that of air, are disposed over surface of the concave and optically
reflective structure 200 (or called optically reflective concave
structure), forming one or multiple OLED emission zones 305/305a on
the bottom surface of the concave structure as shown in FIGS. 8a,
8b, 9a and 9b, or forming one or multiple OLED emission zones
305b/305c that extend to the top edge of the concave area as shown
in FIGS. 10a, 10b, 11a and 11b.
[0069] (3) Further, the relatively transparent material 400/400a
(referred as the index-matching material) having a refractive index
similar to those of the OLED emission layer(s)/emission zone is
disposed over the OLED functional layers 300 within the concave
structure 200 to fill or nearly fill the concave and optically
reflective structure 200. The exposed surface of the index-matching
filling material/layer 400/400a can be flat or curved, as shown in
FIG. 8-11. Filling the index-matching material 400/400a can
increase the overall thickness of functional layers 300 within the
concave and optically reflective area 200 and reduce the number of
reflection (and corresponding optical loss) of the reflected or
total internal reflected light before being re-directed by the
concave and optically reflective structure for optical
out-coupling.
[0070] (4) Also, the refractive indices of various functional
layer(s) 300/400 within the concave and optically reflective area
200 are kept similar or homogeneous (e.g., with refractive indices
n being within .+-.0.2 of that of the emission layer/zone) or
higher than those of the emission layer(s)/zone, so that the
difference in refractive indices and layer structures are not
sufficient to induce total internal reflection (or waveguided
modes) between layers.
[0071] (5) With such an OLED structure, the optical energy L
originally trapped by total internal reflection or reflection of
the material/air interface may be re-directed and be out-coupled to
air by reflection or multiple reflection of the concave and
optically reflective structure 200.
[0072] (6) In such an OLED structure, to effectively re-direct and
out-couple the optical energy originally trapped by total internal
reflection or reflection of the material/air interface, the profile
of the concave structure 200 shall not be too steep (e.g., nearly
vertical or) 90.degree. or be too gentle (e.g., nearly flat or
0.degree.).
[0073] (7) To reduce the optical loss of reflected or total
internal reflected light during reflection/propagation in the
structure, the concave and optical reflective structure should have
a relatively high optical reflectance (e.g., >80%) in the
emission wavelength range.
[0074] (8) To reduce the optical loss of reflected or total
internal reflected light during reflection/propagation in the
structure, various functional layers in the concave and optical
reflective structure should have a relatively high transparency
(e.g., >75%) in the emission wavelength range.
[0075] (9) To reduce the optical loss of reflected or total
internal reflected light during reflection/propagation in the
structure, the ratio between the maximum width and the depth of the
concave and optically reflective structure 200 should be kept small
enough to reduce the number of reflection and total internal
reflection within the structure. For example, the ratio of maximum
width overall the depth is <60 or 30. In an preferred
embodiments, the electroluminescent device with the optical
out-coupling efficiencies is disclosed when the ratio is <30.
Further, the ratio between the maximum width of the concave area
200 and the total thickness of functional layers 300/400 in the
concave and optical reflective structure 200 should be kept small
enough to reduce the number of reflection and total internal
reflection within the structure. For example, the ratio of maximum
width overall the total layer thickness is <60 or 30. In an
preferred embodiments, the electroluminescent device with the
optical out-coupling efficiencies is disclosed when the ratio is
<30.
[0076] (10) If a portion of some functional layers disposed over
the concave and optically reflective structure 200 extends to the
non-concave area (FIG. 8-11), the overall total layer thickness of
such extended part shall be kept much smaller than the depth of the
concave and reflective structure 200 and the overall total layer
thickness disposed within the concave area, to reduce the leakage
of light energy propagating and bouncing within the concave area to
the extended area and to reduce the ratio of light that cannot be
out-coupled by the concave and optically reflective structure
200.
[0077] This invention provides a top-emitting active matrix OLED
display (top-emitting AMOLED) structure that makes use of the above
mentioned OLED structures with high optical out-coupling efficiency
and thus would have enhanced emission efficiency and reduced power
consumption. The array of the above mentioned OLED structures with
high optical out-coupling efficiency are formed over the substrate
having the thin-film transistor (TFT) driving circuit array. An
appropriate electrical interconnection is formed between the TFT
driving circuit array and the OLED array above, so that the TFT
driving circuit array can drive and control the OLED array,
achieving the top-emitting AMOLED.
[0078] There have been some reported approaches for enhancing light
out-coupling of OLEDs, such as micro-lens, surface textures,
scattering, embedded low-index grids, embedded grating/corrugation,
embedded photonic crystals, high-index substrates etc. Although
these different methods/structures can provide enhancement of OLED
light out-coupling to some degree and may be useful for OLED
lighting and/or bottom-emitting OLED structures, they may not be
readily applicable to OLED displays for enhancing light
out-coupling of OLED pixels, due to a few factors and difficulties:
(1) the optical out-coupling structures/processing may not be
compatible with OLED displays, or the optical out-coupling
structures/processing may be too complicated, too small (e.g., need
to use very high-resolution nano-fabrication or nano-processing),
too expensive, or too difficult to integrate with OLED display
structures and processing; (2) the out-coupling structures/effects
may lead to light leakage/diffusion to neighboring pixels and thus
lead to pixel blurring that would degrade the display resolution
and image quality, making them not useful for OLED displays; (3)
the out-coupling structures/effects may lead to optical scattering,
diffusive reflection, diffractive reflection of ambient incident
light and thus lead to degradation of display contrast and image
quality, making them not useful for OLED displays. As such, current
(top-emitting) OLED displays hardly adopt effective light
out-coupling techniques/structures for boosting efficiencies and
power saving, although it is highly desired for mobile
applications.
[0079] The inventions disclosed here, as compared to various prior
arts for enhancing light out-coupling of OLEDs in general could
have the following features/merits for OLED display
applications:
[0080] (1) It could extract otherwise trapped light (e.g.,
waveguided modes or the large-angle total internally reflected
light), giving high optical out-coupling efficiency.
[0081] (2) The extraction mechanism here is rather wavelength
insensitive, therefore good for all R/G/B/W-color OLEDs and good
for both display and lighting applications.
[0082] (3) The extraction structure and mechanism here could
re-mix/re-distribute internal emission of different angles, and
therefore reduce angular dependence (e.g., viewing angle dependent
emission characteristics induced by microcavity effect) of pixel
OLED emission and be beneficial to viewing-angle
characteristics/performance and color performance of OLED
displays.
[0083] (4) The structure here could confine pixel emission mainly
within the concave and reflective structure of the pixel element of
an OLED display, thus reduce leakage of emission of a pixel element
to and re-radiation at neighboring pixels, and would not have pixel
blurring/mixing problems (that would degrade display resolution) as
in other OLED out-coupling structures and techniques.
[0084] (5) When used in the pixel element of OLED displays, the
structure here has no major change in optical effects of incident
ambient light as compared to conventional OLED pixel structures,
and therefore it shall not induce optical scattering, diffusive
reflection, diffractive reflection of ambient incident light and
thus could keep high contrast of the pixel image.
[0085] (6) When using structures having non-planar emission zones
in the OLED display pixel element, they could also increase the
emission area/filling factor/aperture ratio of the OLED pixel,
which is beneficial for OLED displays requiring higher and higher
pixel densities and display resolutions.
[0086] (7) It only slightly modifies current top-emitting AMOLED
structure and processing (e.g., 1-2 more photo-masks during the
fabrication), requires no nano-scale (very high-resolution)
fabrication, and has good compatibility and feasibility with
current AMOLED structures and processing.
[0087] Embodiment of the optically reflective concave structure:
material of the first surface (the bottom surface) is the same as
that of the second surface (the inclined surface) of the optically
reflective concave structure.
[0088] FIGS. 12a, 12b and 12c illustrate several possible types of
the optically reflective concave structure of this invention. The
optically reflective concave structure may be directly formed by an
optically reflective material, selected from the group consisting
of metal and scattering reflector. The optically reflective concave
structure may also be composed of a concave structure and an
optically reflective surface. The material of the optically
reflective surface is selected from the group consisting of metal,
transparent conductive metal-oxide, transparent dielectric,
scattering reflector, distributed Bragg reflector formed by
alternate stacking of high-index/low-index materials, and their
stacking or combinations.
[0089] The first type, which is shown in FIG. 12a, which is formed
by disposing (and patterning) highly optically reflective and
conductive layer(s) 201, such as Al, Ag, Al:Ag alloys, or their
stacks, over the concave structure layer 200, or further disposing
conductive indium tin oxide (ITO), indium zinc oxide (IZO),
aluminum zinc oxide (AZO), gallium zinc oxide (GZO) over the Al
(Ag, Al:Ag alloys, Ag/Al stacks). Such highly optically reflective
and conductive layer(s) 201 can serve as the bottom electrode of
the OLED.
[0090] The second type, which is shown in FIG. 12b, which is formed
by disposing (and patterning) appropriate combinations of
transparent dielectric layers 201a having high reflection, such as
the distributed Bragg reflector (DBR) formed by alternate stacking
of high-index/low-index materials (e.g., ITO/SiO.sub.2,
TiO.sub.2/SiO.sub.2, Ta.sub.2O.sub.5/SiO.sub.2 etc.), over the
concave structure layer 200a.
[0091] The third type, which is shown in FIG. 12c, which is formed
by using a material having strong optical scattering reflection to
directly form the concave structure layer 200b. Both the bottom and
the inclined sides of the concave structure are the scattering
reflective material.
[0092] Below, using the concave and optically reflective structure
of FIG. 12a, two embodiment examples of top-emitting OLEDs and four
embodiment examples top-emitting AMOLEDs having the concave and
optically reflective structures are described. With slight
modification of the processing and processing flows of these
embodiment examples, top-emitting OLEDs and top-emitting AMOLEDs
having the concave and optically reflective structures of FIG. 12b
and FIG. 12c can also be readily implemented.
[0093] Embodiment 1: structure and fabrication method for the
electroluminescent device having the optically reflective concave
structure.
[0094] FIGS. 13a, 13b and 13c illustrate several possible
embodiments of OLEDs having the concave and optically reflective
structure 200, including the structure with the OLED emission zone
305 within the concave area (at the bottom), as shown in FIG. 13a,
and the structure with the OLED emission zone 305b extending to the
side slopes and the top edge of the concave area, as shown in FIGS.
13b and 13c. In all these OLED structures, the concave and
optically reflective structures 200 are first formed on a substrate
100. Then, various functional layers 300 of the OLED, such as
emission layer(s), charge transport layer(s), electrode layer(s),
insulating dielectric layer(s) 301 to define the emission area of
the OLED, and passivation/capping layer(s) 310 etc. that typically
have refractive indices higher than that of air, are disposed over
surface of the concave and optically reflective structure 200,
forming OLED emission zones inside the concave area, as shown in
FIG. 13a, or forming OLED emission zones that extend to the top
edge of the concave area, as shown in FIGS. 13b and 13c. In
disposing OLED functional layers 300, if more than one emitting
layers/units are disposed in the layer structure, then multiple
emission zones 305 may be formed and stacked in the concave and
optically reflective structure 200.
[0095] Below, using the structure of FIG. 13a as the example, one
possible fabrication/processing flow for its fabrication is
illustrated in FIG. 14. Meanwhile, the structures of FIGS. 13b and
13c can be similarly fabricated by slightly modifying the
processing/fabrication flow shown in FIG. 14.
[0096] (a) Dispose a material layer 200 on a substrate 100 for the
formation of the concave structure.
[0097] (b) With using the photo-mask and photolithography, form the
concave structure (a single concave structure or an array of
concave structures) in this material layer through etching of the
material layer or through photo-patterning/developing of a
photopolymer.
[0098] (c) Dispose (and pattern) highly optically reflective
layer(s) 201, such as Al, Ag, Al:Ag alloys, or their stacks, over
the concave structure layer 200, or further disposing conductive
indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc
oxide (AZO), gallium zinc oxide (GZO) over the Al (Ag, Al:Ag
alloys, Ag/Al stacks). Such highly optically reflective and
conductive layer(s) can serve as the bottom electrode of the
OLED.
[0099] (d) Dispose and pattern the insulating dielectric layer(s)
301 (e.g., SiO2, SiNx etc. deposited by PECVD or sputtering) to
define the emission area of the OLED.
[0100] (e) Dispose various functional layers 300 of the OLED, such
as carrier injection layer(s), emission layer(s), charge transport
layer(s) etc. These OLED functional layers 300 can be disposed over
the whole area or selectively only over the concave area (e.g.,
selective deposition through vacuum deposition through a shadow
mask or through ink-jet printing).
[0101] (f) Dispose the semi-transparent or transparent top
electrode 310 of the OLED structure. The semi-transparent or
transparent top electrode 310 could be ITO, IZO, AZO, GZO, thin
metal layer (e.g., <=25 nm thickness) of Al, Ag, Al:Ag alloy,
Mg:Ag alloy, Al/Ag stacks, Mg/Ag stacks etc.
[0102] (g) If necessary, other functional layers, such as the
passivation/capping layer 320, can be further disposed over the top
semi-transparent or transparent electrode 310 of the OLED.
[0103] The concave structure layer 200 can be formed by: (1) the
etching method, or (2) the photo-patterning/developing of a
photopolymer.
[0104] For the etching method, as shown in FIG. 15, the processing
steps might include:
[0105] (1) Dispose a material layer on a substrate for the
formation of the concave structure, such as SiO.sub.2, SiN.sub.x
dielectric material layer(s) deposited by PECVD or sputtering.
[0106] (2) For a photoresist pattern over such a material layer 200
through coating/exposure/developing of a photoresist layer.
[0107] (3) Use the isotropic etching recipe to etch the concave
structure material layer 200 through the opening in the photoresist
layer. Due to lateral etching characteristics of the isotropic
etching, not only the material under the opening will be etched
away, but also a portion of the material under the photoresist
layer and near the edge of the photoresist opening will be
partially etched away, forming a taper structure near the edge of
the photoresist opening. The isotropic etching used could be a wet
etching method or a dry etching method widely reported in the
literature.
[0108] (4) After removal of the photoresist, the layer with concave
structures is obtained.
[0109] For the method of photo-patterning/developing of a
photopolymer, as shown in FIG. 16, the processing steps might
include:
[0110] (1) Dispose a photopolymer layer on a substrate 100 for the
formation of the concave structure 200, such as a negative
photoresist/photopolymer.
[0111] (2) Conduct a patterned (UV) light exposure of the
photopolymer through a photomask pattern. During the exposure, due
to diffraction/diffusion effect near edges of photomask patterns,
there would still be partial exposure/developing for areas under
photomask pattern edges.
[0112] (3) After exposure, conduct development of the negative
photoresist/photopolymer. Un-exposed areas/materials would be
removed by the developer, while UV-light-exposed areas/materials
would remain due to photo-induced cross-linking. Due to partial
exposure/developing effect under photomask pattern edges, the
concave structure layer with tapers is formed after
development.
[0113] With such OLED structures in FIGS. 13a, 13b and 13c, the
optical energy originally trapped by total internal reflection or
reflection of the material/air interface may be re-directed and be
out-coupled to air by the bending of the concave structure or the
change/variation of the layer thicknesses, when propagating in the
layers, as shown in FIGS. 7a-7b.
[0114] To reduce the optical loss of reflected or total internal
reflected light during reflection/propagation in the structure, the
concave and optical reflective structure should have a relatively
high optical reflectance (e.g., >80%) in the emission wavelength
range.
[0115] To reduce the optical loss of reflected or total internal
reflected light during reflection/propagation in the structure,
various functional layers in the concave and optical reflective
structure should have a relatively high transparency (e.g.,
>75%) in the emission wavelength range.
[0116] To reduce the optical loss of reflected or total internal
reflected light during reflection/propagation in the structure, the
ratio between the maximum width of the concave area and the total
thickness of functional layers in the concave and optical
reflective structure should be kept small enough to reduce the
number of reflection and total internal reflection within the
structure. For example, the ratio of maximum width overall the
total layer thickness is <200, 180, 150, 100, 80 or 50. In an
preferred embodiments, the electroluminescent device with the
optical out-coupling efficiencies is disclosed when the ratio is
<50.
[0117] Embodiment 2: structure and fabrication method for the
electroluminescent device having the optically reflective concave
structure with the flat or curved exposed surface of the
index-matching material.
[0118] FIGS. 17a, 17b and 17c illustrate several other possible
embodiments of OLEDs having the concave and optically reflective
structure 200, including the structure with the OLED emission zone
305 within the concave area in FIG. 17a and the structure with the
OLED emission zone 305b extending to the top edge of the concave
area in FIGS. 17b and 17c. Their structures and possible
fabrication are similar to those shown in FIGS. 13a, 13b and 13c
and FIG. 14, and yet a relatively transparent material 400
(referred as the index-matching filling material) having a
refractive index similar to those of the OLED emission
layer(s)/emission zone 305/305b is further disposed over the OLED
functional layers 300 within the concave area to fill or nearly
fill the concave and optically reflective structure. Filling the
index-matching material 400 can increase the overall thickness of
functional layers within the concave and optically reflective area
and reduce the number of reflection (and corresponding optical
loss) of the reflected or total internal reflected light before
being re-directed by the concave and optically reflective structure
for optical out-coupling. In disposing OLED functional layers, if
more than one emitting layers/units are disposed in the layer
structure, then multiple emission zones may be formed and stacked
in the concave and optically reflective structure.
[0119] Also, the refractive indices of various functional layer(s)
within the concave and optically reflective area are kept similar
or homogeneous (e.g., with refractive indices n being within
.+-.0.2 of that of the emission layer/zone) or higher than those of
the emission layer(s)/zone, so that the difference in refractive
indices and layer structures are not sufficient to induce total
internal reflection (or waveguided modes) between layers.
[0120] With these OLED structures, the optical energy originally
trapped by total internal reflection or reflection of the
material/air interface may be re-directed and be out-coupled to air
by reflection or multiple reflection of the concave and optically
reflective structure.
[0121] In these OLED structures, to effectively re-direct and
out-couple the optical energy originally trapped by total internal
reflection or reflection of the material/air interface, the profile
(side slopes) of the concave structure shall not be too steep
(e.g., nearly vertical or 90.degree. side slope) or be too gentle
(e.g., nearly flat or 0.degree. side slope).
[0122] To reduce the optical loss of reflected or total internal
reflected light during reflection/propagation in the structure, the
concave and optical reflective structure should have a relatively
high optical reflectance (e.g., >80%) in the emission wavelength
range.
[0123] To reduce the optical loss of reflected or total internal
reflected light during reflection/propagation in the structure,
various functional layers in the concave and optical reflective
structure should have a relatively high transparency (e.g.,
>75%) in the emission wavelength range.
[0124] To reduce the optical loss of reflected or total internal
reflected light during reflection/propagation in the structure, the
ratio between the maximum width and the depth of the concave and
optically reflective structure should be kept small enough to
reduce the number of reflection and total internal reflection
within the structure. For example, the ratio of maximum width
overall the depth is <60 or 30. In an preferred embodiments, the
electroluminescent device with the optical out-coupling
efficiencies is disclosed when the ratio is <30. Further, the
ratio between the maximum width of the concave area and the total
thickness of functional layers in the concave and optical
reflective structure should be kept small enough to reduce the
number of reflection and total internal reflection within the
structure. For example, the ratio of maximum width overall the
total layer thickness is <60 or 30. In an preferred embodiments,
the electroluminescent device with the optical out-coupling
efficiencies is disclosed when the ratio is <30.
[0125] If a portion of some functional layers disposed over the
concave and optically reflective structure extends outside to the
non-concave area, the overall total layer thickness of such
extended part shall be kept much smaller than the depth of the
concave and reflective structure and the overall total layer
thickness disposed within the concave area, to reduce the leakage
of light energy propagating and bouncing within the concave area to
the extended area and to reduce the ratio of light that cannot be
out-coupled by the concave and optically reflective structure.
[0126] The disposition of the index-matching filling material 400
in FIGS. 17a, 17b and 17c may be conducted by several possible
ways:
[0127] (1) Dispose a material with appropriate thickness and
refractive index (n) by vacuum deposition/evaporation to reduce the
dip depth of the concave area. The selective deposition/evaporation
of the index-matching capping/filling material layer may be
conducted through a shadow mask to define its
area/pattern/range.
[0128] (2) Selectively dispose liquid or gel-state index-matching
fluid/oil, adhesive, gel, resin, encapsulation material etc. to
fill the concave area. If necessary, solidify these index-matching
filling materials by subsequent curing. The selective disposition
of these liquid or gel-state index-matching capping/filling
materials may be conducted by ink-jet printing to define its
area/pattern/range and to control the filling material amount and
filling thickness.
[0129] If the index-matching filling materials applied to the
concave area are liquid or gel, one may further make use of their
surface tension to make the surface of the index-matching material
layer curved or non-planar (e.g., lens-like surface profile), as
illustrated in FIGS. 18a, 18b and 18c. It may benefit direct
out-coupling of OLED emission or reduce of the number of
reflections (and corresponding optical loss) before being
out-coupled, further enhancing optical out-coupling efficiency of
OLEDs.
[0130] Embodiment example 3: top-emitting active matrix OLED
display (top-emitting AMOLED) having the optically reflective
concave structure.
[0131] FIG. 19 shows the schematic integration structure for the
pixel of a top-emitting AMOLED. It has a pixel definition layer-PDL
P (or planarization & interlayer) of an appropriate thickness,
which has tapered opening for defining the pixel OLED emission area
and also serves to planarize surface corrugation caused by
TFTs/electrode bus lines/interconnection/other structures of the
backplane below.
[0132] FIG. 19 shows that there is a concave structure in the
AMOLED pixel OLED structure. By using such a concave structure in
the AMOLED pixel OLED structure, by forming patterned reflective
electrode E over the surface of the concave structure, and by
making its electrical contact to the TFT interconnection 500
beneath, OLED pixels having the concave and optically reflective
structure can be formed. By adding one or two more photo-mask
processing steps in the AMOLED fabrication, various top-emitting
AMOLED architectures having the concave and optically reflective
structure 200(201), as shown in FIG. 20a, 20b, 20c, can be
implemented. In the structure of FIG. 20a, the OLED emission area
is defined at the planar bottom of the concave structure 200 (i.e.,
with planar OLED emission zone) by the patterned opening in the
emission-zone definition layer 301. Meanwhile in the structures of
FIGS. 20b and 20c, the OLED emission area is extended to the side
slopes till the top edge of the concave area (i.e., with non-planar
OLED emission zone), as defined by the patterned opening in the
emission-zone definition layer 301 or the patterned reflective
electrode 201 over the surface of the concave structure 200. In
disposing OLED functional layers 300 including the top (semi)
transparent electrode 310, if more than one emitting layers/units
are disposed in the layer structure, then multiple emission zones
may be formed and stacked in the concave and optically reflective
structure 200.
[0133] Embodiment example 4: top-emitting active matrix OLED
display (top-emitting AMOLED) having the optically reflective
concave structure with the flat or curved exposed surface of the
index-matching material.
[0134] With the structures shown in FIG. 20a, 20b, 20c as the
basis, a relatively transparent material 400/400a (referred as the
index-matching filling material) having a refractive index similar
to those of the OLED emission layer(s)/emission zone can be further
disposed over the OLED functional layers 300/310 within the concave
area to fill or nearly fill the concave and optically reflective
structure 200/201, forming the structures shown in FIG. 21a, 21b,
21c or FIG. 22a, 22b, 22c. In disposing OLED functional layers
300/310, if more than one emitting layers/units are disposed in the
layer structure, then multiple emission zones may be formed and
stacked in the concave and optically reflective structure
200/201.
[0135] Embodiment example 5: top-emitting active matrix OLED
display (top-emitting AMOLED) having the optically reflective
concave structure.
[0136] With the structures shown in FIGS. 20a, 20b, 20c as the
basis, through appropriate patterning and opening in the concave
structure layer and layers beneath, the bottom reflective electrode
(and also the optically reflective coating over the concave area
200) of the pixel OLED can also serve as the interconnection
conductor 500a with the TFT below, forming various top-emitting
AMOLED architectures having the concave and optically reflective
structure 200 as shown in FIGS. 23a, 23b, 23c. In the structure of
FIG. 23a, the OLED emission area is defined at the planar bottom of
the concave structure 200 (i.e., with planar OLED emission zone) by
the patterned opening in the emission-zone definition layer 301.
Meanwhile in the structures of FIGS. 23b and 23c, the OLED emission
area is extended to the side slopes till the top edge of the
concave area (i.e., with non-planar OLED emission zone), as defined
by the patterned opening in the emission-zone definition layer 301
or the patterned reflective electrode over the surface of the
concave structure 200. In disposing OLED functional layers 300
including the semi-transparent or transparent top electrode 310, if
more than one emitting layers/units are disposed in the layer
structure, then multiple emission zones may be formed and stacked
in the concave and optically reflective structure 200.
[0137] Embodiment example 6: top-emitting active matrix OLED
display (top-emitting AMOLED) having the optically reflective
concave structure with the flat or curved exposed surface of the
index-matching material
[0138] With the structures shown in FIGS. 23a, 23b, 23c as the
basis, a relatively transparent material 400/400a (referred as the
index-matching filling material) having a refractive index similar
to those of the OLED emission layer(s)/emission zone can be further
disposed over the OLED functional layers within the concave area to
fill or nearly fill the concave and optically reflective structure,
forming the structures shown in FIGS. 24a, 24b, 24c or FIG. 25a,
25b, 25c. In disposing OLED functional layers, if more than one
emitting layers/units are disposed in the layer structure, then
multiple emission zones may be formed and stacked in the concave
and optically reflective structure.
[0139] Embodiment of the optically reflective concave structure:
material of the first surface is different from that of the second
surface.
[0140] In addition to several possible types of the concave and
optically reflective structures illustrated in FIGS. 12a, 12b and
12c, several more possible concave and optically reflective
structures that combine different reflective material layers are
illustrated in FIGS. 26a, 26b and 26c.
[0141] The first type, which is shown in FIG. 26a, is formed by
first disposing a highly optically reflective material layer(s)
over the substrate and then forming a concave structure layer on
such a highly reflective layer with a material having strong
optical scattering reflection. The highly optically reflective
material layer(s) over the substrate could be conductive material
like Al, Ag, Al:Ag alloys, their stacks or material stacks of
transparent conductor like indium tin oxide (ITO), indium zinc
oxide (IZO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO)
over the Al (Ag, Al:Ag alloys, Ag/Al stacks). The highly optically
reflective material layer(s) over the substrate could also be
dielectric DBR.
[0142] The second type, which is shown in FIG. 26b, is formed by
first disposing a highly optically reflective material layer(s)
over the substrate, forming a concave structure layer on such a
highly reflective layer, and then disposing (and patterning)
appropriate combinations of transparent dielectric layers having
high reflection, such as the distributed Bragg reflector formed by
alternate stacking of high-index/low-index materials (e.g.,
ITO/SiO.sub.2, TiO.sub.2/SiO.sub.2, Ta.sub.2O.sub.5/SiO.sub.2
etc.), over the concave structure side slopes. The highly optically
reflective material layer(s) over the substrate could be conductive
material like Al, Ag, Al:Ag alloys, their stacks or material stacks
of transparent conductor like indium tin oxide (ITO), indium zinc
oxide (IZO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO)
over the Al (Ag, Al:Ag alloys, Ag/Al stacks). The highly optically
reflective material layer(s) over the substrate could also be a
highly reflective layer with a material having strong optical
scattering reflection.
[0143] The third type, which is shown in FIG. 26c, is formed by
first disposing a highly optically reflective material layer(s)
over the substrate, forming a concave structure layer on such a
highly reflective layer, and then disposing (and patterning) highly
optically reflective and conductive layer(s) over the side slopes
of the concave structure. The highly optically reflective layer
over the substrate could be the distributed Bragg reflector formed
by alternate stacking of high-index/low-index materials (e.g.,
ITO/SiO.sub.2, TiO.sub.2/SiO.sub.2, Ta.sub.2O.sub.5/SiO.sub.2
etc.). The highly optically reflective material layer(s) over the
substrate could also be a highly reflective layer with a material
having strong optical scattering reflection. The highly optically
reflective and conductive material layer(s) over the side slopes of
concave structures could be conductive material like Al, Ag, Al:Ag
alloys, their stacks or material stacks of transparent conductor
like indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc
oxide (AZO), gallium zinc oxide (GZO) over the Al (Ag, Al:Ag
alloys, Ag/Al stacks).
[0144] Below, using the concave and optically reflective structure
of FIG. 26a, two embodiment examples of top-emitting OLEDs and two
embodiment examples of top-emitting AMOLEDs having the concave and
optically reflective structures are described. With slight
modification of the processing and processing flows of these
embodiment examples, top-mitting OLEDs and top-emitting AMOLEDs
having the concave and optically reflective structures of FIG. 26b
and FIG. 26c can also be readily implemented.
[0145] Embodiment example 7: OLED having the optically reflective
concave structure.
[0146] FIGS. 27a, 27b illustrate possible embodiments of
top-emitting OLEDs having the concave and optically reflective
structure, including the structure with the OLED emission zone
within the concave area in FIG. 27a and the structure with the OLED
emission zone extending to the top edge of the concave area in FIG.
27b. In these OLED structures, the concave and optically reflective
structures are first formed on a substrate 100. Then, various
functional layers 300 of the OLED, such as emission layer(s),
charge transport layer(s), electrode layer(s), and
passivation/capping layer(s) 310 etc. that typically have
refractive indices higher than that of air, are disposed over
surface of the concave and optically reflective structure, forming
OLED emission zones inside the concave area, as shown in FIG. 27a,
or forming OLED emission zones that extend to the top edge of the
concave area, as shown in FIG. 27b. In disposing OLED functional
layers, if more than one emitting layers/units are disposed in the
layer structure, then multiple emission zones may be formed and
stacked in the concave and optically reflective structure.
[0147] Embodiment example 8: OLED having the optically reflective
concave structure with the flat or curved exposed surface of the
index-matching material.
[0148] FIGS. 28a and 28b illustrate possible embodiments of
top-emitting OLEDs having the concave and optically reflective
structure, including the structure with the OLED emission zone
within the concave area in FIG. 28a and the structure with the OLED
emission zone extending to the top edge of the concave area in FIG.
28b. Their structures and possible fabrication are similar to those
shown in FIGS. 27a, 27b and FIG. 14, and yet a relatively
transparent material 400/400a (referred as the index-matching
filling material) having a refractive index similar to those of the
OLED emission layer(s)/emission zone is further disposed over the
OLED functional layers 300/310 within the concave area to fill or
nearly fill the concave and optically reflective structure. Filling
the index-matching material 400/400a can increase the overall
thickness of functional layers within the concave and optically
reflective area and reduce the number of reflection (and
corresponding optical loss) of the reflected or total internal
reflected light before being re-directed by the concave and
optically reflective structure for optical out-coupling. In
disposing OLED functional layers, if more than one emitting
layers/units are disposed in the layer structure, then multiple
emission zones may be formed and stacked in the concave and
optically reflective structure.
[0149] If the index-matching filling materials applied to the
concave area are liquid or gel, one may further make use of their
surface tension to make the surface of the index-matching material
layer curved or non-planar (e.g., lens-like surface profile), as
illustrated in FIGS. 29a and 29b. It may benefit direct
out-coupling of OLED emission or reduce of the number of
reflections (and corresponding optical loss) before being
out-coupled, further enhancing optical out-coupling efficiency of
OLEDs.
[0150] Embodiment example 9: top-emitting active matrix OLED
display (top-emitting AMOLED) having the optically reflective
concave structure.
[0151] With the structure shown in FIG. 27a as the basis, possible
embodiments of top-emitting AMOLED structures containing pixel
OLEDs having the concave and optically reflective structure are
shown in FIG. 30. In the structure of FIG. 30a, the OLED emission
zone is within the concave area; in the structure of FIG. 30b, the
OLED emission zone extends to the side slopes and the top edge of
the concave area, forming non-planar OLED emission zones. In
disposing OLED functional layers, if more than one emitting
layers/units are disposed in the layer structure, then multiple
emission zones may be formed and stacked in the concave and
optically reflective structure.
[0152] Embodiment example 10: top-emitting active matrix OLED
display (top-emitting AMOLED) having the optically reflective
concave structure with the flat or curved exposed surface of the
index-matching material.
[0153] With the structures shown in FIGS. 30a, 30b as the basis, a
relatively transparent material (referred as the index-matching
filling material) having a refractive index similar to those of the
OLED emission layer(s)/emission zone can be further disposed over
the OLED functional layers within the concave area to fill or
nearly fill the concave and optically reflective structure, forming
the structures shown in FIGS. 31a, 31b or FIGS. 32a, 32b. In
disposing OLED functional layers, if more than one emitting
layers/units are disposed in the layer structure, then multiple
emission zones may be formed and stacked in the concave and
optically reflective structure.
[0154] The above embodiments are only used to illustrate the
principles of the present invention, and they should not be
construed as to limit the present invention in any way. The above
embodiments can be modified by those with ordinary skill in the art
without departing from the scope of the present invention as
defined in the following appended claims.
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