U.S. patent application number 17/671752 was filed with the patent office on 2022-07-07 for oleds for micro transfer printing.
The applicant listed for this patent is X Display Company Technology Limited. Invention is credited to Christopher Bower, Ronald S. Cok, Matthew Meitl.
Application Number | 20220216413 17/671752 |
Document ID | / |
Family ID | 1000006138594 |
Filed Date | 2022-07-07 |
United States Patent
Application |
20220216413 |
Kind Code |
A1 |
Bower; Christopher ; et
al. |
July 7, 2022 |
OLEDS FOR MICRO TRANSFER PRINTING
Abstract
An organic light-emitting diode (OLED) structure includes an
organic light-emitting diode having a first electrode, one or more
layers of organic material disposed on at least a portion of the
first electrode, and a second electrode disposed on at least a
portion of the one or more layers of organic material. At least a
portion of a tether extending from a periphery of the organic
light-emitting diode. The organic light-emitting diodes can be
printable organic light-emitting diode structures that are micro
transfer printed over a display substrate to form a display.
Inventors: |
Bower; Christopher;
(Raleigh, NC) ; Meitl; Matthew; (Durham, NC)
; Cok; Ronald S.; (Rochester, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
X Display Company Technology Limited |
Dublin |
|
IE |
|
|
Family ID: |
1000006138594 |
Appl. No.: |
17/671752 |
Filed: |
February 15, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16255596 |
Jan 23, 2019 |
11289652 |
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17671752 |
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14869369 |
Sep 29, 2015 |
10230048 |
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16255596 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 27/3225 20130101;
H01L 51/56 20130101; H01L 51/0013 20130101; H01L 2227/323 20130101;
H01L 51/5206 20130101; H01L 51/5253 20130101; H01L 51/0023
20130101; H01L 51/003 20130101; H01L 51/50 20130101; H01L 51/5221
20130101; H01L 27/3206 20130101 |
International
Class: |
H01L 51/00 20060101
H01L051/00; H01L 51/56 20060101 H01L051/56; H01L 51/50 20060101
H01L051/50; H01L 27/32 20060101 H01L027/32; H01L 51/52 20060101
H01L051/52 |
Claims
1-40. (canceled)
41. A method of making an OLED structure, comprising: providing a
source substrate; patterning a sacrificial layer on the source
substrate; patterning a first electrode on the sacrificial layer;
patterning one or more layers of organic material on at least a
portion of the patterned first electrode; and patterning a second
electrode on at least a portion of the one or more layers of
organic material to form an OLED structure.
42. The method of claim 41, comprising removing at least a portion
of the sacrificial layer, thereby partially releasing the OLED
structure from the source substrate.
43. The method of claim 42, comprising micro transfer printing the
OLED structure from the source substrate to a display
substrate.
44. The method of claim 41, wherein the one or more layers of
organic material are one or more layers of organic material that
emit blue light and the OLED structure is a blue OLED structure
that emits blue light when a current is applied thereto.
45. The method of claim 44, comprising: forming a red OLED
structure that emits red light when a current is applied thereto,
comprising: providing a second source substrate; patterning a
second sacrificial layer on or in the second source substrate;
patterning a first electrode on the second sacrificial layer;
patterning one or more layers of organic material that emit red
light on at least a portion of the patterned first electrode on the
second sacrificial layer; and patterning a second electrode on at
least a portion of the one or more layers of organic material that
emit red light; and forming a green OLED structure that emits green
light when a current is applied thereto, comprising: providing a
third source substrate; patterning a third sacrificial layer on or
in the third source substrate; patterning a first electrode on the
third sacrificial layer; patterning one or more layers of organic
material that emit green light on at least a portion of the
patterned first electrode on the third sacrificial layer; and
patterning a second electrode on at least a portion of the one or
more layers of organic material that emit green light.
46. The method of claim 45, comprising: micro transfer printing the
red OLED structure from the red source substrate to a display
substrate; micro transfer printing the green OLED structure from
the green source substrate to the display substrate; and micro
transfer printing the blue OLED structure from the blue source
substrate to the display substrate.
47. The method of claim 45, wherein at least ten thousand,
one-hundred thousand, one million, or ten million OLEDs are on each
source substrate.
48. The method of claim 41, wherein patterning the one or more
layers of organic material on the patterned first electrode
comprises depositing the layers of organic material through a fine
metal shadow mask.
49. The method of claim 41, wherein patterning the one or more
layers of organic material on the patterned first electrode and
patterning the second electrode on the one or more layers of
organic material comprises: blanket depositing the layers of
organic material over an area of the source substrate; blanket
depositing the second electrode over the layers of organic
material; forming a patterned protective layer over the second
electrode, the patterned protective layer defining the pattern of
the one or more layers of organic material; patterning the second
electrode by exposing the second electrode to an active material
that removes second electrode material exposed to line-of-flight of
the active material; and patterning the one or more layers of
organic material by exposing the one or more layers of organic
material to an active material that removes the one or more layers
of organic material exposed to the line-of-flight of the active
material.
50. The method of claim 49, wherein patterning the one or more
layers of organic material on the patterned first electrode and
patterning the second electrode on the one or more layers of
organic material comprises: removing the patterned protective
layer.
51. The method of claim 50, wherein patterning the one or more
layers of organic material on the patterned first electrode and
patterning the second electrode on the one or more layers of
organic material comprises: providing additional patterned second
electrode material to form the patterned second electrode and
protect the one or more layers of organic material.
52. The method of claim 41, wherein the organic light-emitting
diode is a top emitter.
53. The method of claim 41, wherein the organic light-emitting
diode is a bottom emitter.
54. The method of claim 41, wherein the organic-light emitting
diode a light-emissive area of less than 1600 square microns.
55. The method of claim 41, wherein the organic-light emitting
diode has at least one of a width from 5 to 10 .mu.m, 10 to 20
.mu.m, or 20 to 50 .mu.m, a length from 5 to 10 .mu.m, 10 to 20
.mu.m, or 20 to 50 .mu.m, and a height from 2 to 5 .mu.m, 4 to 10
.mu.m, 10 to 20 .mu.m, or 20 to 50 .mu.m.
56-67. (canceled)
Description
FIELD OF THE INVENTION
[0001] The present invention relates to organic light-emitting
diode (OLED) displays and to micro transfer printing.
BACKGROUND OF THE INVENTION
[0002] Flat-panel displays are widely used in conjunction with
computing devices, in portable devices, and for entertainment
devices such as televisions. Such displays typically employ a
plurality of pixels distributed over a display substrate to display
images, graphics, or text. In a color display, each pixel includes
light emitters that emit light of different colors, such as red,
green, and blue. For example, liquid crystal displays (LCDs) employ
liquid crystals to block or transmit light from a backlight behind
the liquid crystals and organic light-emitting diode (OLED)
displays rely on passing current through a layer of organic
material that glows in response to the current. Displays using
inorganic light emitting diodes (LEDs) are also in widespread use
for outdoor signage and have been demonstrated in a 55-inch
television.
[0003] The various light-emitting technologies have different
characteristics, advantages, and disadvantages. For example, liquid
crystals are simple to control and have a highly developed and
sophisticated technological infrastructure. Organic LEDs are area
emitters, can be more efficient and flexible, and are demonstrated
in a very thin form factor. Inorganic light-emitting diodes are
very efficient and provide relatively saturated light in an
environmentally robust structure. Lasers are also efficient,
provide a virtually monochromatic light, but have a limited viewing
angle. None of these technologies, however, meet all of a display
viewer's needs under all circumstances.
[0004] Organic light-emitting diodes are widely used in portable
electronic devices with displays and in some televisions. Organic
LEDs are area emitters, can be efficient and flexible, can have a
very thin form factor, and have an excellent viewing angle.
However, the process used to manufacture OLED displays has some
challenging steps. An OLED emitter typically includes several
layers, for example a hole-injection layer, a light-emitting layer,
and an electron-injection layer. The hole-injection layer is coated
on a first electrode such as an anode and a second electrode such
as a cathode is formed on an electron-injection layer.
Alternatively, an electron-injection layer is formed on a cathode
and the anode is formed on a hole-injection layer.
[0005] One type of OLED display is made with a common unpatterned
light emitter for all pixels and patterned color filters that
filter the light from each light-emitter in the display. Different
color filters produce different colors and the common light emitter
emits white light, for example a combination of blue and yellow
light. This display type is similar to the color-filter approach
found in LCDs and suffers from the loss of approximately two thirds
of the emitted light in the color filters.
[0006] Another type of OLED display uses different organic material
patterned over a display substrate. The different OLED materials
are chosen to emit different colors of light and are patterned to
form pixels, typically arranged in stripes. The strip pattern is
formed by depositing organic material through a fine metal shadow
mask. A different mask is used for each different set of materials,
or at least for the different light-emitting layers. The alignment
of the masks before deposition is difficult, and the repeated use
of the masks can damage deposited materials. Moreover, the masks
must be periodically cleaned, are easily damaged, difficult to
make, and expensive.
[0007] There is a need, therefore, for devices, systems and methods
for providing OLED light emitters that have improved efficiency,
reduced costs, and fewer mechanical process steps.
SUMMARY OF THE INVENTION
[0008] The present invention provides structures, devices and
methods for organic light-emitting diodes and color displays that
require fewer or no shadow masks for evaporative deposition of
organic materials. The organic light-emitting diode structures can
be micro transfer printed and organic light-emitting diode
structures that each emit different colors of light can be
separately constructed on separate source substrates, released from
the source substrate, and micro transfer printed to a destination
display substrate. The organic light-emitting diode structures and
methods mitigate the problems encountered with repeated use of fine
metal shadow masks, such as alignment to a common display substrate
and damage to organic materials deposited on the display
substrate.
[0009] Moreover, in an embodiment, the use of fine metal shadow
masks is unnecessary for patterning evaporated organic materials.
Higher resolution OLED displays are thereby enabled.
[0010] In one aspect, the disclosed technology includes a structure
including an organic light-emitting diode (OLED) having a first
electrode, one or more layers of organic material disposed on at
least a portion of the first electrode, and a second electrode
disposed on at least a portion of the one or more layers of organic
material; and at least a portion of a tether extending from a
periphery of the organic light-emitting diode.
[0011] In certain embodiments, at least a portion of the first
electrode is transparent.
[0012] In certain embodiments, at least a portion of the second
electrode is transparent.
[0013] In certain embodiments, the layers of organic material
comprise one or more of a hole-injection layer, a light-emitting
layer, and an electron-injection layer.
[0014] In certain embodiments, the OLED has a light-emitting area
that has a dimension parallel to the first electrode that is less
than or equal to 40 microns, less than or equal to 20 microns, less
than or equal to 10 microns, or less than or equal to 5
microns.
[0015] In certain embodiments, the OLED has a light-emitting area
that is less than or equal to 1600 square microns, less than or
equal to 800 square microns, less than or equal to 400 square
microns, less than or equal to 200 square microns, less than or
equal to 100 square microns, or less than or equal to 50 square
microns.
[0016] In certain embodiments, the first electrode comprises a
transparent electrode in electrical contact with an opaque first
electrode portion, and a transparent insulator, wherein the
transparent insulator is at least partly in a common layer with the
opaque first electrode portion.
[0017] In certain embodiments, the transparent electrode is
disposed on a transparent insulator.
[0018] In certain embodiments, the first electrode comprises a
first protrusion and the second electrode comprises a second
protrusion separate from the first protrusion, the first and second
protrusions extending in a direction from the second electrode to
the first electrode.
[0019] In certain embodiments, the first electrode is a unitary
electrical conductor.
[0020] In certain embodiments, the organic light-emitting diode is
a top emitter.
[0021] In certain embodiments, the organic light-emitting diode is
a bottom emitter.
[0022] In certain embodiments, the organic-light emitting diode a
light-emissive area of less than 1600 square microns, less than or
equal to 800 square microns, less than or equal to 400 square
microns, less than or equal to 200 square microns, less than or
equal to 100 square microns, or less than or equal to 50 square
microns.
[0023] In certain embodiments, the organic-light emitting diode has
at least one of a width from 5 to 10 .mu.m, 10 to 20 .mu.m, or 20
to 50 .mu.m, a length from 5 to 10 .mu.m, 10 to 20 .mu.m, or 20 to
50 .mu.m, and a height from 2 to 5 .mu.m, 4 to 10 .mu.m, 10 to 20
.mu.m, or 20 to 50 .mu.m.
[0024] In certain embodiments, the structure includes a source
substrate having a portion defining an anchor; and a sacrificial
layer formed on the source substrate and adjacent to the anchor,
wherein the OLED is disposed on the sacrificial layer and the
tether is connected to the anchor.
[0025] In certain embodiments, an oxide layer or a pre-determined
designated portion of the source substrate.
[0026] In certain embodiments, the sacrificial layer comprises a
cavity between the organic light-emitting diode and the source
substrate.
[0027] In certain embodiments, the structure includes a plurality
of OLED structures formed on the source substrate, wherein the one
or more layers of organic material in each of the OLED structures
is the same.
[0028] In certain embodiments, at least one of the one or more
layers of organic material emits red light, green light, or blue
light.
[0029] In certain embodiments, the structure includes first and
second OLED structures formed on the source substrate and wherein
the first OLED structure comprises at least one layer of organic
material that emits a first color of light and the second OLED
structure comprises at least one layer of organic material that
emits a second color of light different from the first color of
light.
[0030] In certain embodiments, the structure includes a third OLED
structure formed on the source substrate, wherein the third OLED
structure comprises at least one layer of organic material that
emits a third color of light different from the first color of
light and different from the second color of light.
[0031] In certain embodiments, the first color of light is red, the
second color of light is green, and the third color of light is
blue.
[0032] In certain embodiments, the portion of a tether extending
from the periphery of the organic light-emitting diode is a portion
of a broken tether.
[0033] In certain embodiments, the structure includes a first
conductive protrusion extending from the structure and electrically
connected to the first electrode; and a second conductive
protrusion extending from the structure and electrically connected
to the second electrode.
[0034] In another aspect, the disclosed technology includes a
display having printable organic light-emitting diode structures,
including: a display substrate; one or more organic light-emitting
diode structures described above and herein disposed on the display
substrate; a first electrical conductor electrically connected to
the first electrode; and a second electrical conductor electrically
connected to the second electrode.
[0035] In certain embodiments, at least one of the first electrical
conductor and the second electrical conductor is located on the
display substrate.
[0036] In certain embodiments, one or more of the OLED structures
are grouped into pixels and the display comprises a pixel
controller located on the display substrate electrically connected
to the first and second electrodes of the pixels in the group to
control the light output from the OLED structures.
[0037] In certain embodiments, the display includes one or more
inorganic light-emitting diodes, wherein the one or more OLED
structures comprises a first OLED structure that emits light of a
first color and a second inorganic light-emitting diode that emits
light of a second color different from the first color.
[0038] In certain embodiments, the one or more OLED structures
comprises at least a first OLED structure that emits light of a
first color and a second OLED structure that emits light of a
second color different from the first color.
[0039] In certain embodiments, two or more of the OLED structures
are grouped into pixels, each pixel including: a first OLED
structure that emits light of the first color; a second OLED
structure that emits light of the second color; and a pixel
substrate, separate and distinct from the display substrate and the
source substrate, on which the first and second OLED structures are
disposed, wherein the pixel substrate is disposed on the display
substrate.
[0040] In certain embodiments, the display includes a pixel
controller located on the pixel substrate electrically connected to
the first and second electrodes of each of the first and second
OLED structures in the pixel to control the light output from the
first and second OLED structures.
[0041] In certain embodiments, the organic light-emitting diode is
a top emitter.
[0042] In certain embodiments, the organic light-emitting diode is
a bottom emitter.
[0043] In certain embodiments, the organic-light emitting diode a
light-emissive area of less than 1600 square microns, less than or
equal to 800 square microns, less than or equal to 400 square
microns, less than or equal to 200 square microns, less than or
equal to 100 square microns, or less than or equal to 50 square
microns.
[0044] In certain embodiments, the organic-light emitting diode has
at least one of a width from 5 to 10 .mu.m, 10 to 20 .mu.m, or 20
to 50 .mu.m, a length from 5 to 10 .mu.m, 10 to 20 .mu.m, or 20 to
50 .mu.m, and a height from 2 to 5 .mu.m, 4 to 10 .mu.m, 10 to 20
.mu.m, or 20 to 50 .mu.m.
[0045] In certain embodiments, the display substrate has a
thickness from 5 to 10 microns, 10 to 50 microns, 50 to 100
microns, 100 to 200 microns, 200 to 500 microns, 500 microns to 0.5
mm, 0.5 to 1 mm, 1 mm to 5 mm, 5 mm to 10 mm, or 10 mm to 20
mm.
[0046] In certain embodiments, the display substrate comprises a
polymer, plastic, resin, polyimide, PEN, PET, metal, metal foil,
glass, a semiconductor, or sapphire.
[0047] In certain embodiments, the display substrate has a
transparency greater than or equal to 50%, 80%, 90%, or 95% for
visible light.
[0048] In certain embodiments, the organic light-emitting diode,
when energized, emits light in a direction opposite the display
substrate.
[0049] In certain embodiments, the organic light-emitting diode,
when energized, emits light through the display substrate.
[0050] In another aspect, the disclosed technology includes a
method of making an OLED structure, including: providing a source
substrate; patterning a sacrificial layer on the source substrate;
patterning a first electrode on the sacrificial layer; patterning
one or more layers of organic material on at least a portion of the
patterned first electrode; and patterning a second electrode on at
least a portion of the one or more layers of organic material to
form an OLED structure.
[0051] In certain embodiments, the method includes removing at
least a portion of the sacrificial layer, thereby partially
releasing the OLED structure from the source substrate.
[0052] In certain embodiments, the method includes micro transfer
printing the OLED structure from the source substrate to a display
substrate.
[0053] In certain embodiments, the one or more layers of organic
material are one or more layers of organic material that emit blue
light and the OLED structure is a blue OLED structure that emits
blue light when a current is applied thereto.
[0054] In certain embodiments, the method includes forming a red
OLED structure that emits red light when a current is applied
thereto, including: providing a second source substrate; patterning
a second sacrificial layer on or in the second source substrate;
patterning a first electrode on the second sacrificial layer;
patterning one or more layers of organic material that emit red
light on at least a portion of the patterned first electrode on the
second sacrificial layer; and patterning a second electrode on at
least a portion of the one or more layers of organic material that
emit red light; and forming a green OLED structure that emits green
light when a current is applied thereto, including: providing a
third source substrate; patterning a third sacrificial layer on or
in the third source substrate; patterning a first electrode on the
third sacrificial layer; patterning one or more layers of organic
material that emit green light on at least a portion of the
patterned first electrode on the third sacrificial layer; and
patterning a second electrode on at least a portion of the one or
more layers of organic material that emit green light.
[0055] In certain embodiments, the method includes micro transfer
printing the red OLED structure from the red source substrate to a
display substrate; micro transfer printing the green OLED structure
from the green source substrate to the display substrate; and micro
transfer printing the blue OLED structure from the blue source
substrate to the display substrate.
[0056] In certain embodiments, the at least ten thousand,
one-hundred thousand, one million, or ten million OLEDs are on each
source substrate.
[0057] In certain embodiments, patterning the one or more layers of
organic material on the patterned first electrode comprises
depositing the layers of organic material through a fine metal
shadow mask.
[0058] In certain embodiments, patterning the one or more layers of
organic material on the patterned first electrode and patterning
the second electrode on the one or more layers of organic material
includes: blanket depositing the layers of organic material over an
area of the source substrate; blanket depositing the second
electrode over the layers of organic material; forming a patterned
protective layer over the second electrode, the patterned
protective layer defining the pattern of the one or more layers of
organic material; patterning the second electrode by exposing the
second electrode to an active material that removes second
electrode material exposed to the line-of-flight of the active
material; and patterning the one or more layers of organic material
by exposing the one or more layers of organic material to an active
material that removes the one or more layers of organic material
exposed to the line-of-flight of the active material.
[0059] In certain embodiments, patterning the one or more layers of
organic material on the patterned first electrode and patterning
the second electrode on the one or more layers of organic material
includes: removing the patterned protective layer.
[0060] In certain embodiments, patterning the one or more layers of
organic material on the patterned first electrode and patterning
the second electrode on the one or more layers of organic material
includes: providing additional patterned second electrode material
to form the patterned second electrode and protect the one or more
layers of organic material.
[0061] In certain embodiments, the organic light-emitting diode is
a top emitter.
[0062] In certain embodiments, the organic light-emitting diode is
a bottom emitter.
[0063] In certain embodiments, the organic-light emitting diode a
light-emissive area of less than 1600 square microns, less than or
equal to 800 square microns, less than or equal to 400 square
microns, less than or equal to 200 square microns, less than or
equal to 100 square microns, or less than or equal to 50 square
microns.
[0064] In certain embodiments, the organic-light emitting diode has
at least one of a width from 5 to 10 .mu.m, 10 to 20 .mu.m, or 20
to 50 .mu.m, a length from 5 to 10 .mu.m, 10 to 20 .mu.m, or 20 to
50 .mu.m, and a height from 2 to 5 .mu.m, 4 to 10 .mu.m, 10 to 20
.mu.m, or 20 to 50 .mu.m.
[0065] In another aspect, the disclosed technology includes a wafer
of printable organic light-emitting diodes, including: a source
substrate; a plurality of organic light-emitting diodes formed on
the substrate, each organic light-emitting diode having a first
electrode, one or more layers of organic material disposed on at
least a portion of the first electrode, and a second electrode
disposed on at least a portion of the one or more layers of organic
material; one or more anchors on the source substrate; and a
plurality of tethers, each organic light-emitting diode releasably
secured to the source substrate by at least one anchor and at least
one tether.
[0066] In certain embodiments, the wafer includes a sacrificial
layer at least partially between the organic light-emitting diodes
and the source substrate, wherein the plurality of organic
light-emitting diodes are disposed on the sacrificial layer.
[0067] In certain embodiments, an oxide layer or a pre-determined
designated portion of the source substrate.
[0068] In certain embodiments, the sacrificial layer comprises a
cavity between the organic light-emitting diode and the source
substrate.
[0069] In certain embodiments, there is an air gap between the
organic light-emitting diodes and the source substrate.
[0070] In certain embodiments, the one or more layers of organic
material in each of the organic light-emitting diodes is the
same.
[0071] In certain embodiments, at least one of the one or more
layers of organic material emits red light, green light, or blue
light when a current is applied thereto.
[0072] In certain embodiments, at least ten thousand, one-hundred
thousand, one million, or ten million OLEDs are on the source
substrate.
[0073] In certain embodiments, the organic light-emitting diodes
are top emitter.
[0074] In certain embodiments, the organic light-emitting diodes
are bottom emitters.
[0075] In certain embodiments, the organic-light emitting diodes
have a light-emissive area of less than 1600 square microns, less
than or equal to 800 square microns, less than or equal to 400
square microns, less than or equal to 200 square microns, less than
or equal to 100 square microns, or less than or equal to 50 square
microns.
[0076] In certain embodiments, the organic-light emitting diodes
have at least one of a width from 5 to 10 .mu.m, 10 to 20 .mu.m, or
20 to 50 .mu.m, a length from 5 to 10 .mu.m, 10 to 20 .mu.m, or 20
to 50 .mu.m, and a height from 2 to 5 .mu.m, 4 to 10 .mu.m, 10 to
20 .mu.m, or 20 to 50 .mu.m.
[0077] Organic light emitters have better power conversion
efficiencies at low current density than some inorganic light
emitters. It is an object of the present invention to provide
organic emitters that supplement the emitter population of displays
made from assemblies of micro scale inorganic LEDs. It is also an
object of the present invention to provide photoluminescent
down-converters for blue or violet micro-assembled inorganic
LEDs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0078] The foregoing and other objects, aspects, features, and
advantages of the present disclosure will become more apparent and
better understood by referring to the following description taken
in conjunction with the accompanying drawings, in which:
[0079] FIG. 1 is a cross section of an embodiment of the present
invention;
[0080] FIGS. 2A-2I are cross sections of successive structures
useful in making the structure of FIG. 1 in an embodiment of the
present invention;
[0081] FIG. 3 is a cross section of an alternative embodiment of
the present invention;
[0082] FIGS. 4A and 4B are top views and bottom views respectively
of the structure in FIG. 3 in an embodiment of the present
invention;
[0083] FIGS. 5A-5J are cross sections of successive structures
useful in making the structure of FIG. 3 in an embodiment of the
present invention;
[0084] FIG. 6 is a cross section of an alternative top-emitter or
bottom-emitter embodiment of the present invention; and
[0085] FIGS. 7A-7O are cross sections of successive structures
useful in making the structures of FIGS. 1, 3, and 5 in an
alternative embodiment of the present invention that does not
require shadow masks;
[0086] FIG. 8 is a perspective of a display in an embodiment of the
present invention;
[0087] FIG. 9 is a perspective of a pixel having a separate
substrate according to an embodiment of the present invention;
[0088] FIG. 10 is a perspective of a display in an embodiment of
the present invention using the pixels of FIG. 9; and
[0089] FIGS. 11 and 12 are flow diagrams illustrating methods in
various embodiments of the present invention.
[0090] The features and advantages of the present disclosure will
become more apparent from the detailed description set forth below
when taken in conjunction with the drawings, in which like
reference characters identify corresponding elements throughout. In
the drawings, like reference numbers generally indicate identical,
functionally similar, and/or structurally similar elements. The
figures are not drawn to scale since the variation in size of
various elements in the Figures is too great to permit depiction to
scale.
DETAILED DESCRIPTION OF THE INVENTION
[0091] Referring to the cross section of FIG. 1, in an embodiment
of the present invention an organic light-emitting diode (OLED)
structure 10 includes an organic light-emitting diode 65 having a
first electrode 55, one or more layers of organic material 60
disposed on at least a portion of the first electrode 55, and a
second electrode 52 disposed on at least a portion of the one or
more layers of organic material 60. The OLED structure 10 includes
at least a portion of a tether 12 extending from a periphery of the
organic light-emitting diode 65. In an embodiment, the OLED
structure 10 is a micro transfer printable OLED 65.
[0092] In the embodiment of FIG. 1, the first electrode 55 includes
a first electrode portion 50 and a transparent electrode 40 that is
in electrical contact with the first electrode portion 50. The
first electrode portion 50 can be opaque, for example made of an
electrically conductive metal such as aluminum, silver, gold,
tungsten, or titanium. The transparent electrode 40 can be any
transparent conductor such as a transparent conductive metal oxide
such as indium tin oxide or aluminum zinc oxide. The second
electrode 52 can be a metal layer made of a conductive metal such
as aluminum, silver, gold, tungsten, or titanium and can be made of
the same material as the first electrode portion 50, or a different
material.
[0093] The OLED 65 can be constructed on a transparent insulator 30
and an insulator 32. The insulator 32 can be transparent and
comprise the same material as the transparent insulator 30 or the
insulator 32 can be a different, opaque material. The transparent
insulator 30 or insulator 32 can be, for example, silicon dioxide
or silicon nitride. The transparent electrode 40 is formed at least
partly on the transparent insulator 30 and the transparent
insulator 30 is at least partly in a common layer with the opaque
first electrode portion 50. The transparent insulator 30 transmits
light emitted from the one or more layers of organic material 60.
The insulator 32 electrically insulates the first electrode portion
50 from the second electrode 52 so that a voltage difference can be
established between the first and second electrodes 55, 52 causing
current to flow between the first and second electrodes 55, 52
through the one or more layers of organic material 60, causing at
least one of the one or more layers of organic material 60 to emit
light.
[0094] The insulator 32 prevents electrical shorts between the
first electrode portion 50 and the second electrode 52 and allows
the first electrode 55 to extend beyond the second electrode 52
enabling an external electrical connection to the first electrode
55, for example an external electrical connection on a display
substrate (not shown in FIG. 1).
[0095] The one or more layers of organic material 60 can be
evaporatively deposited on the transparent electrode 40 and can
include a hole-injection layer, a light-emitting layer, and an
electron-injection layer. Bank insulators 34 formed on the edges or
corners of the transparent electrode 40 prevents electrical shorts
between the transparent electrode 40 and the second electrode 52 at
the edges or corners of the transparent electrode 40.
[0096] The OLED structure 10 includes a tether 12 physically
connecting the OLED 65 extending from a periphery of the organic
light-emitting diode 65. In the embodiment of FIG. 1, the tether 12
is an extension of the transparent insulator 30 beyond the OLED 65
and is attached to a portion of a source substrate 20 forming an
anchor 14. A sacrificial layer 18 is formed beneath the OLED
structure 10 so that the OLED structure 10 is only connected to the
source substrate 20 by the tether 12 to the anchor 14. Thus, the
OLED structure 10 can be released from the source substrate 20 by
contacting the OLED 65 with a stamp, pressing the stamp against the
OLED 65 to fracture the tether 12. The OLED 65 can then be micro
transfer printed to a destination substrate such as a display
substrate (not shown in FIG. 1).
[0097] The sacrificial layer 18 can be a cavity that is etched out
from under the OLED 65 to form the tether 12 and OLED structure 10.
Alternatively, according to embodiments of the present invention,
the sacrificial layer 18 is a physical layer, such as an oxide
layer on the source substrate 20 on which the OLED 65 is
constructed. In another embodiment, the source substrate 20 is a
semiconductor substrate, such as silicon (1 0 0) or silicon (1 1
1), and the sacrificial layer 18 is a pre-determined designated
portion of the source substrate 20.
[0098] The cross sections of FIGS. 2A-2I and the flow diagram of
FIG. 11 illustrate successive steps in making an embodiment of the
present invention. As shown in FIG. 2A, a source substrate 20 is
provided in step 100. The source substrate 20 can be any substrate
on which the subsequent structures can be formed and can include a
glass, plastic, or semiconductor substrate having opposing
substantially planar surfaces on which lithographic processes can
be performed. The embodiment described uses a semiconductor
substrate, for example silicon (1 0 0) or silicon (1 1 1).
[0099] For clarity and brevity of exposition, in the following
steps and also with respect to FIGS. 5A-5J, repeated references are
made to forming a patterned layer or structure. Patterned layers
are typically made in the photolithographic arts by first
depositing a blanket layer of a desired material, for example by
evaporation or sputtering. A blanket layer is unpatterned and
covers the exposed area of a substrate. A photoresist layer, either
positive or negative and for example SUB, is then deposited in a
blanket layer over the desired material and exposed to a pattern of
electromagnetic radiation such as ultra-violet radiation to
pattern-wise cure the photoresist. The uncured photoresist is then
removed to expose a pattern of the desired material. The exposed
desired material is then etched, for example with a wet etchant, a
dry etch, a plasma, reactive ions, or other active materials to
remove the exposed desired material. Optionally, the cured
photoresist is then removed, for example using an etchant specific
to the cured photoresist, leaving a pattern of the desired
material.
[0100] Referring to FIG. 2B, a first electrode portion 50 is
deposited and patterned on or in the source substrate 20 in step
110. For example, the first electrode portion 50 can be a metal
such as aluminum, titanium, tungsten, gold, silver, or other
electrically conductive materials including conductive inks,
semiconductors, or doped semiconductors.
[0101] A layer of transparent insulator 30 is patterned over the
first electrode portion 50 in step 120, leaving an exposed gap in
the transparent insulator 30, as shown in FIG. 2C. A suitable
transparent insulator 30 is silicon nitride or silicon dioxide. The
transparent insulator 30 can be partially transparent, for example
50%, 70%, 80%, 90%, or 95% transparent to visible light. Two
portions of transparent insulator 30 (a left and a right portion)
are shown in FIG. 2C. The right portion can be opaque and does not
need to be transparent. As shown in FIG. 1, the right portion of
the insulating layer is labeled as 32, an insulator and can be
formed and patterned separately from the transparent insulator 30
and can be a different material than the transparent insulator 30.
In an embodiment, however, both the transparent insulator 30 and
insulator 32 of FIG. 1 are transparent and are made in a common
process with common materials so that the insulator 32 is also a
transparent insulator 30.
[0102] Referring next to FIG. 2D, in step 130 a transparent
electrode 40 is patterned over the transparent insulator 30 and in
electrical contact with the first electrode portion 50. The
transparent electrode 40 is therefore in electrical contact with
the first electrode portion 50 and the first electrode 55 includes
both the first electrode portion 50 and the transparent electrode
40. As shown in FIG. 2E, bank insulators 34 are formed and
patterned in step 140 on the edges of the transparent electrode 40.
The bank insulators 34 can be made of the same materials as the
transparent insulator 30 or insulator 32, or a different insulating
material. The bank insulators 34 can, but need not, be
transparent.
[0103] As shown in FIG. 2F, one or more layers of organic material
60 are patterned over the transparent electrode 40 in step 150. The
one or more layers of organic material 60 can extend, but need not
extend, over the bank insulators 34 and transparent insulators 30
(and insulator 32 as shown in FIG. 1). In an embodiment, the one or
more layers of organic material 60 are deposited by evaporation and
patterned with a fine metal mask placed over the transparent
conductor 40 and the bank insulators 34. The fine metal mask has
openings corresponding to the areas in which it is desired to
deposit the organic layers, for example the exposed portion of the
transparent electrode 40 between the bank insulators 34. Elsewhere,
any evaporated organic material is deposited on the fine metal
mask. Alternatively, the one or more layers of organic material 60
are patterned using photolithographic processes described
below.
[0104] Referring next to FIG. 2G, the second electrode 52 is
patterned over the one or more layers of organic material 60 in
step 160. The first and second electrodes 55, 52 and the one or
more layers of organic material 60 form an organic light-emitting
diode or OLED 65. When a voltage is supplied across the first and
second electrodes 55, 52 so that an electrical current flows
between the first and second electrodes 55, 52 through the one or
more layers of organic material 60, light is emitted from one or
more of the organic material layers.
[0105] As shown in FIG. 2H, the transparent insulator 30 or
insulator 32 (FIG. 1) is further patterned to expose the first
electrode portion 50 in step 170. The sacrificial layer 18 is then
removed in step 180 from beneath the first electrode portion 50 and
transparent insulator (dielectric) 30, for example by etching (FIG.
2I). In one embodiment of the present invention, the sacrificial
layer 18 is simply a portion of the source substrate 20 that is
etched, for example to form a cavity, as illustrated in FIGS. 1 and
2I. In another embodiment a layer different from the source
substrate 20 is patterned on the source substrate 20, for example
an oxide or nitride layer. The OLED structure 10 is formed on the
sacrificial layer 18, with the optional addition of an etch stop
layer to protect the OLED structure 10 from the sacrificial layer
18 etch when it is removed in step 180 to form a cavity. After
etching, the sacrificial layer 18 is a cavity.
[0106] The sacrificial layer 18 is patterned on the source
substrate 20 so that the OLED 65 is completely undercut and so that
a tether 12 extends from the periphery or edge of the OLED 65 to an
anchor 14. The anchor 14 can be a portion of the source substrate
20 that is not removed when the sacrificial layer 18 is removed to
form the cavity. The tether 12 can be a portion of the transparent
insulator 30 (as shown) or a portion of the first or second metal
electrodes 55, 52, or the bank insulator 34 (as shown in FIG. 10
and discussed further below). Because of the tether 12, anchor 14,
and underlying sacrificial layer 18, the OLED structure 10 is
suitable for micro transfer printing. During the micro transfer
printing process, the tether 12 is fractured leaving only a portion
of the tether 12 as a part of the OLED structure 10 of the present
invention, and the OLED structure 10 can be transferred to a
destination substrate such as a display substrate.
[0107] The OLED structure 10 of FIG. 1 and as made by the process
described in FIGS. 2A-2I includes first and second electrodes 55,
52. After the OLED structure 10 is micro transfer printed to a
destination substrate, conventional photolithographic methods can
be used to electrically connect the first and second electrodes 55,
52 to a control, power, or ground circuit.
[0108] An alternative OLED structure 10 according to an embodiment
of the present invention is illustrated in FIG. 3 and a method of
making the OLED structure 10 is illustrated in the successive cross
section illustrations of FIGS. 4A-4L. As shown in FIG. 3, the first
electrode 55 includes a first protrusion 53 and the second
electrode 52 includes a second protrusion 54 spatially and
electrically separate from the first protrusion 53. The first and
second protrusions 53, 54 extend in a direction from the second
electrode 52 to the first electrode 55, i.e., toward the source
substrate 20. The remainder of the OLED 65 and OLED structure 10
are similar to those described above with respect to FIG. 1.
[0109] FIGS. 4A and 4B illustrate top and bottom views of the OLED
structure 10 of FIG. 3 respectively, excluding the source substrate
20 and the transparent insulator 30 in the bottom view. As viewed
from the top and as shown in FIG. 4A, the OLED structure 10
includes a first electrode portion 50 extending to one side of the
OLED structure 10. The insulator 32 separates the first electrode
portion 50 from the second electrode 52. The insulator 32 (which
can be the transparent insulator 30) extends to the other side of
the OLED structure 10 and, where it extends past the protrusion 54,
forms the tether 12.
[0110] As viewed from the bottom and as shown in FIG. 4B, the OLED
structure 10 includes a first electrode portion 50 extending to one
side of the OLED structure 10. The transparent insulator 30
separates the first electrode portion 50 from the bank insulator
34. The one or more layers of organic material 60 can (but need
not) extend past the bank insulator 34 and the second electrode 52
likewise can (but need not) extend past the one or more layers of
organic material 60. The insulator 32 (which can be the transparent
insulator 30) extends to the other side of the OLED structure 10
and, where it extends past the protrusion 54 (which is a portion of
the second electrode 52), forms the tether 12.
[0111] The cross sections of FIGS. 5A-5J and the flow diagram of
FIG. 11 illustrate successive steps in making an embodiment of the
present invention. As shown in FIG. 5A, a source substrate 20 is
provided in step 100 with spatially separated indentations formed
in the source substrate 20, for example by anisotropic etching,
above a portion of the source substrate 20 pre-defined as the
sacrificial layer 18. The source substrate 20 can be any substrate
on which the subsequent structures can be formed and can include a
glass, plastic, or semiconductor substrate having opposing
substantially planar surfaces on which lithographic processes can
be performed. The embodiment described uses a semiconductor
substrate, for example silicon (1 0 0) or silicon (1 1 1).
[0112] Referring to FIG. 5B, in step 110 a first electrode portion
50 is deposited and patterned on or in one of the indentations in
the source substrate 20 and a portion of the second electrode 52 is
deposited and patterned on or in the other of the indentations in
the source substrate 20. For example, the first electrode portion
50 or second electrode portions 52 can be a metal such as aluminum,
titanium, tungsten, gold, silver, or other electrically conductive
materials including conductive inks, semiconductors, or doped
semiconductors.
[0113] A layer of transparent insulator 30 is patterned over the
first electrode portion 50 in step 120, leaving an exposed gap in
the transparent insulator 30, as shown in FIG. 2C. A suitable
transparent insulator 30 is silicon nitride or silicon dioxide. The
transparent insulator 30 can be partially transparent, for example
50%, 70%, 80%, 90%, or 95% transparent to visible light. A
transparent insulator 30 is shown on the left in FIG. 5C. The right
portion can be opaque and does not need to be transparent. As shown
in FIG. 3, the right portion of the insulating layer is labeled as
32, an insulator and can be formed and patterned separately from
the transparent insulator 30 and can be a different material than
the transparent insulator 30. In an embodiment, however, both the
transparent insulator 30 and insulator 32 of FIG. 1 are transparent
and are made in a common process with common materials so that the
insulator 32 is also a transparent insulator 30.
[0114] Referring next to FIG. 5D, in step 130 a transparent
electrode 40 is patterned over the transparent insulator 30 and in
electrical contact with the first electrode portion 50. The
transparent electrode 40 is therefore in electrical contact with
the first electrode portion 50 and the first electrode 55 includes
both the first electrode portion 50 and the transparent electrode
40. As shown in FIG. 5E, a via is opened in the transparent
insulator 30 to expose a portion of the second electrode 52. In an
embodiment, this step is combined with the step illustrated in FIG.
5F. As shown in FIG. 5F, bank insulators 34 are formed and
patterned in step 140 on the edges of the transparent electrode 40.
The bank insulators 34 can be made of the same materials as the
transparent insulator 30 or insulator 32, or a different insulating
material. The bank insulators 34 can, but need not, be
transparent.
[0115] As shown in FIG. 5G, one or more layers of organic material
60 are patterned over the transparent electrode 40 in step 150. The
one or more layers of organic material 60 can, but need not, extend
over the bank insulators 34 and transparent insulators 30 (and
insulator 32 as shown in FIG. 3). In an embodiment, the one or more
layers of organic material 60 are deposited by evaporation and
patterned with a fine metal mask placed over the transparent
conductor 40 and the bank insulators 34. The fine metal mask has
openings corresponding to the areas in which it is desired to
deposit the organic layers; for example, the exposed portion of the
transparent electrode 40 between the bank insulators 34. Elsewhere,
any evaporated organic material is deposited on the fine metal
mask. Alternatively, the one or more layers of organic material 60
are patterned using photolithographic processes described
below.
[0116] Referring next to FIG. 5H, the second electrode 52 is
patterned over the one or more layers of organic material 60 in
step 160 and is formed in electrical contact with the portion of
the second electrode 52 through the via. The first and second
electrodes 55, 52 and the one or more layers of organic material 60
form an organic light-emitting diode or OLED 65. When a voltage is
supplied across the first and second electrodes 55, 52 so that an
electrical current flows between the first and second electrodes
55, 52 through the one or more layers of organic material 60, light
is emitted from one or more of the organic material layers.
[0117] As shown in FIG. 5I, the transparent insulator 30 or
insulator 32 (FIG. 1) is further patterned to expose the first
electrode portion 50 in step 170. The sacrificial layer 18 is then
removed in step 180 from beneath the first electrode portion 50 and
transparent insulator (dielectric) 30, for example by etching (FIG.
5J). In one embodiment of the present invention, the sacrificial
layer 18 is simply a portion of the source substrate 20 that is
etched, for example etched to form a cavity, as illustrated in
FIGS. 3 and 5J. In another embodiment a layer different from the
source substrate 20 is patterned on the source substrate 20, for
example an oxide or nitride layer. The OLED structure 10 is formed
on the sacrificial layer 18, with the optional addition of an etch
stop layer to protect the OLED structure 10 from the sacrificial
layer 18 etch when it is removed in step 180 to form a cavity.
After etching, the sacrificial layer 18 is a cavity.
[0118] The sacrificial layer 18 is patterned on the source
substrate 20 so that the OLED 65 is completely undercut and so that
a tether 12 extends from the periphery or edge of the OLED 65 to an
anchor 14. The anchor 14 can be a portion of the source substrate
20 that is not removed when the sacrificial layer 18 is removed to
form the cavity. The tether 12 can be a portion of the transparent
insulator 30 (as shown) or a portion of the first or second metal
electrodes 55, 52, or the bank insulator 34 (as shown in FIG. 10
and discussed further below). Because of the tether 12, anchor 14,
and underlying sacrificial layer 18, the OLED structure 10 is
suitable for micro transfer printing. During the micro transfer
printing process, the tether 12 is fractured leaving only a portion
of the tether 12 as a part of the OLED structure 10 of the present
invention, and the OLED structure 10 can be transferred to a
destination substrate such as a display substrate.
[0119] The OLED structure 10 of FIG. 1 and as made by the process
described in FIGS. 2A-2I includes first and second electrodes 55,
52. In certain embodiments, one or more steps may be omitted. After
the OLED structure 10 is micro transfer printed to a destination
substrate, conventional photolithographic methods can be used to
electrically connect the first and second electrodes 55, 52 to a
control, power, or ground circuit.
[0120] Another embodiment of the present invention illustrate in
the cross section of FIG. 6 uses a unitary first electrode 55. By
unitary it is meant that the first electrode 55 consists of only
one kind of material in a single structure in contrast to the first
electrode 55 of the embodiments of FIGS. 1 and 3, in which the
first electrode 55 has two parts, a first electrode portion 50 and
a transparent electrode portion 40. As shown in FIG. 6, the
separate transparent electrode 40 is omitted and the tether 12 is
formed by the bank insulator 34. The structure shown in FIG. 6 can
also be used with the first and second protrusions 53, 54 shown in
the embodiment of FIG. 3.
[0121] The evaporated organic materials can be patterned by using a
fine metal shadow mask that prevents the deposition of organic
particles on portions of a substrate covered by the shadow mask. In
an embodiment of the present invention, the organic materials are
patterned using photolithographic methods. Because the present
invention contemplates the deposition of only a single set of
organic materials on a source substrate 20 and multiple colors in a
display are provided with different sets of organic materials on
respective different source substrates 20 rather than on a common
substrate, the photolithographic process do not damage pre-existing
layers of organic materials.
[0122] FIG. 7A illustrates a portion of an OLED structure 10
corresponding to the structures of FIGS. 2F and 5G except that the
one or more layers of organic material 60 are unpatterned.
Referring to FIG. 7B, an unpatterned layer of electrically
conductive material comprising the second electrode 52 is deposited
on the unpatterned one or more layers of organic material 60.
[0123] Next, as shown in FIG. 7C, a protective layer 70 is
patterned on the unpatterned second electrode 52 and then exposed
to an active material, such as an etchant, a dry etchant, an ion
etchant, or a plasma. The active material removes the exposed
portions of the second electrode 52 as shown in FIG. 7D. The
process is then optionally repeated with the same or a different
etchant (FIG. 7E) to form the patterned one or more layers of
organic materials 60 illustrated in FIG. 7F.
[0124] The patterned protective layer 70 is optionally removed (not
shown) or coated with a second layer 56 of the electrical conductor
of the second electrode 52 (FIG. 7G) and patterned to further
protect any exposed edges of the one or more layers of organic
materials 60 (FIG. 7H). If not removed earlier, the patterned
protective layer 70 is optionally removed (FIG. 7I) and an
additional layer of second electrode 52 material is optionally
provided (FIG. 7J). After patterning the organic materials layer 60
a barrier material 71 may be deposited and patterned to encapsulate
the organic materials and at least a portion of the second
electrode 52, optionally having at least one opening to provide
access to the second electrode 52. A third conductive layer 72 that
like the barrier material 71 has moisture or environmental
protection characteristics may be deposited and patterned over some
portion of the organic materials and the second electrode, thereby
forming (FIG. 7M) a protecting encapsulation layer composed of a
combination of barrier material 71 and the third conductive layer
72. The insulator 32 is then patterned (FIG. 7K) and the
sacrificial layer 18 etched (FIG. 7L) to form the OLED structure
10, optionally having the protecting encapsulation layer (FIG. 7N).
In some embodiments, the organic structure is photoluminescent and
contains only organic layers and transparent dielectric or barrier
layers with no exposed electrical terminals (FIG. 7O).
[0125] Therefore, a method of patterning the one or more layers of
organic material 60 on the patterned first electrode 55 and
patterning the second electrode 52 on the one or more layers of
organic material 60 includes blanket depositing the layers of
organic material 60 over an area of the source substrate 20,
blanket depositing the second electrode 52 over the layers of
organic material 60, and forming a patterned protective layer 70
over the second electrode 52. The patterned protective layer
defines the pattern of the one or more layers of organic material
60. The second electrode 52 is patterned by exposing the second
electrode 52 to an active material that removes second electrode
material exposed to the line-of-flight of the active material. The
one or more layers of organic material 60 are patterned by exposing
the one or more layers of organic material 60 to an active material
that removes the one or more layers of organic material 60 exposed
to the line-of-flight of the active material. The patterned
protective layer is optionally removed. Additional patterned second
electrode material is optionally provided to form the patterned
second electrode 52 and protect the one or more layers of organic
material 60. In an embodiment, the active material is a gas, a
plasma, or not a liquid.
[0126] The process described in FIGS. 7A-7L does not require the
use of fine metal shadow masks and is therefore not limited by the
sizes of the mechanical structures inherent in the shadow masks.
Instead, higher resolution photolithographic techniques are used
and, in consequence, smaller OLED devices for higher resolution
displays are possible. Therefore, according to an embodiment of the
present invention, OLED 65 has a light-emitting area that has a
dimension parallel to the extent of the first electrode 55 that is
less than or equal to 40 microns, less than or equal to 20 microns,
less than or equal to 10 microns, or less than or equal to 5
microns. Alternatively, or in addition, the OLED 65 has a
light-emitting area that is less than or equal to 1600 square
microns, less than or equal to 800 square microns, less than or
equal to 400 square microns, less than or equal to 200 square
microns, less than or equal to 100 square microns, or less than or
equal to 50 square microns.
[0127] According to different embodiments of the present invention,
the OLED structure 10 can have a top-emitter configuration or a
bottom-emitter configuration. FIG. 1 and FIGS. 2A-2I illustrate a
structure and method for a bottom-emitter embodiment in which light
from the one or more layers of organic material 60 passes through
the bottom, transparent electrode 40 and transparent insulator 30.
Referring to FIG. 6, a top-emitter embodiment uses a unitary opaque
first electrode 55 that extends between the bank insulators 34 and
under the one or more layers of organic material 60. The bank
insulators 34 are also helpful to insulate the transparent
electrode 40 from the second electrode 52. The second electrode 52
is transparent, for example made of a metal oxide such as indium
tin oxide or aluminum zinc oxide. In other embodiments, for example
alternative configurations of FIGS. 1 and 3, the transparent
electrode 40 is replaced with an opaque and preferably reflective
electrode and the second electrode 52 is transparent. In these
embodiments of the present invention, light emitted from the one or
more layers of organic material 60 in response to current flowing
between the first and second electrodes 55, 52 passes through the
top, transparent second electrode 52.
[0128] As shown in FIGS. 1, 3, and 6, OLED structures 10 of the
present invention can be constructed over a sacrificial layer 18 on
a source substrate 20. The source substrate 20 has a portion
defining an anchor 14 and the sacrificial layer 18 is formed on the
source substrate 20 and adjacent to the anchor 14. The OLED 65 is
disposed on the sacrificial layer 18 and the tether 12 is connected
to the anchor 14. This OLED structure 10 is adapted for micro
transfer printing to a destination substrate such as a display
substrate.
[0129] According to further embodiments of the present invention, a
plurality of OLED structures 10 are formed on the source substrate
20. In one embodiment, the one or more layers of organic material
60 in each of the OLED structures 10 is the same and at least one
of the one or more layers of organic material 60 emits red light,
green light, or blue light.
[0130] Alternatively, first and second OLED structures 10 are
formed on the source substrate 20. The first OLED structure 10
includes at least one layer of organic material that emits a first
color of light and the second OLED structure 10 includes at least
one layer of organic material that emits a second color of light
different from the first color of light. Additionally, a third OLED
structure 10 can be formed on the source substrate 20 that includes
at least one layer of organic material that emits a third color of
light different from the first color of light and different from
the second color of light. The first color of light can be red, the
second color of light can be green, and the third color of light
can be blue.
[0131] Referring to the perspective of FIG. 8, a micro transfer
printed OLED display 82 having printable organic light-emitting
diode structures 10 includes a display substrate 80 having one or
more organic light-emitting diode structures 10 disposed on the
display substrate 80. A first electrical conductor 98 is
electrically connected to the first electrode 55 and a second
electrical conductor 99 is electrically connected to the second
electrode 52. In various embodiments, the first electrical
conductor 98 or the second electrical conductor 99 is located on
the display substrate 80 or the first and second electrical
conductors 98, 99 are both located on the display substrate 80. The
first and second electrical conductors 98, 99 can be connected to
wires or form a bus 96 that is connected to a controller 92. The
controller 92 provides signals, power, or ground through the wires
96 and the first and second electrical conductors 98, 99 to control
the organic light-emitting diode structures 10 to emit light.
Although for clarity, the OLED structures 10 are shown
interconnected serially by the first and second electrical
conductors 98, 99, in an alternative embodiment, the OLED
structures 10 can be controlled using conventional column and row
drivers.
[0132] The OLED structures 10 can be grouped into pixels 90. The
pixels 90 can have OLED structures 10 that all emit the same color
of light or the pixels 90 can be full-color pixels 90 that each
have different OLED structures 10. For example, the pixels 90 can
include at least a first OLED structure 10 that emits light of a
first color and a second OLED structure 10 that emits light of a
second color different from the first color. The pixels 90 can also
include a third OLED structure 10 that emits light of third color
different from the first and second colors. The colors can be red,
green, and blue and the first OLED structure 10 can be a red OLED
structure 10R that emits red light, the second OLED structure 10
can be a green OLED structure 10G that emits green light, and the
third OLED structure 10 can be a blue OLED structure 10B that emits
blue light.
[0133] In an alternative embodiment of the present invention, not
shown, a color display includes both organic light-emitting diodes
and inorganic light-emitting diodes. Thus, the one or more OLED
structures 10 can include a first OLED structure 10 that emits
light of a first color and a second inorganic light-emitting diode
that emits light of a second color different from the first color.
Both the organic and inorganic light-emitting diodes can be micro
transfer printed from a source substrate 20 to the display
substrate 80 to form a heterogeneous display. For example, the red
light emitter can be a red OLED and the green and blue light
emitters can be inorganic light emitters.
[0134] In a further embodiment of the present invention the display
includes pixel controllers 94 (shown in FIG. 9) associated with or
a part of the pixels 90 that are electrically connected to the
first and second electrodes 55, 52 of the OLED structures 10 in the
pixel 90 group to control the OLED structures 10 to emit light. The
pixel controllers 94 can be an integrated circuit that includes
control circuits responsive to the controller 92 through the wires
96 and first and second electrical conductors 98, 99.
[0135] In an embodiment of the present invention and as shown in
FIG. 9, the pixel controllers 94 and the OLED structures 10 in a
pixel 90 are disposed on a pixel substrate 84 that is separate and
distinct from the display substrate 80 and forms a pixel component
16. The pixel substrate 84 can be a semiconductor substrate on or
in which the pixel controller circuits are formed (not shown), or
the pixel substrate 84 can also be separate and distinct from the
pixel controller 94 substrate (as shown).
[0136] As shown in FIG. 10, the pixel components 16 are then
disposed on the display substrate 80, for example by micro transfer
printing to form a micro-transfer printed display 82 or by using
pick-and-place technology. The pixel components 16 can be surface
mount components.
[0137] The present invention provides an advantage over structures
and methods of the prior art in that OLED structures 10 of the
present invention emitting different colors of light can each be
made on a different source substrate 20 so that each source
substrate 20 can include OLED structures 10 that emit light of only
a single color. This reduces alignment and tolerance issues and
avoid repeatedly contacting the source substrate 20 with shadow
masks. Referring to FIG. 12, a red source substrate 20R is a source
substrate 20 with an organic layer that emits red light, a green
source substrate 20G is a source substrate 20 with an organic layer
that emits green light, and a blue source substrate 20B is a source
substrate 20 with an organic layer that emits blue light. Each of
the red, green, and blue source substrates are different and
separate source substrates 20 that can each supply a red, green, or
blue OLED structure 10R, 10G, or 10B, respectively.
[0138] As shown in FIG. 12, a red source substrate 20R is provided
in step 100R, a green source substrate 20G is provided in step
100G, a blue source substrate 20B is provided in step 100B, and a
destination substrate such as a displays substrate 80 is provided
in step 105. As shown in FIG. 11, the steps 110 through 140 form a
first electrode structure in step 101 and the steps 160-180 form a
second electrode structure in step 103. After the different source
and destination substrates 20, 80 are provided in FIG. 12, the
first electrodes 55 are separately and independently formed on each
of the red, green, and blue source substrates 20R, 20G, and 20B in
step 101. One or more layers of organic material 60 that emit red
light are then patterned on the red source substrate 20R, one or
more layers of organic material 60 that emit green light are then
patterned on the green source substrate 20G, and one or more layers
of organic material 60 that emit blue light are then patterned on
the blue source substrate 20B in steps 150R, 150G, 150B,
respectively. The second electrodes 52 are separately and
independently formed on each of the red, green, and blue layers of
organic material on each of the red, green, and blue source
substrates 20R, 20G, and 20B in step 103. The blue OLED structures
10B are then micro transfer printed to the destination substrate
80, the green OLED structures 10G are micro transfer printed to the
destination substrate 80, and the red OLED structures 1OR are micro
transfer printed to the destination substrate 80 in steps 190B,
190G, and 190R to form the display structure illustrated in FIG. 8.
The steps 190B, 190G, and 190R can be performed in any order. If
pixel components 16 are desired, the red, green, and blue OLED
structures 10R, 10G, 10B from the red, green, and blue source
substrates 20R, 20G, and 20B, respectively, are each micro transfer
printed onto the pixel substrate 84 and then the pixel substrates
84 are disposed on the destination substrate 80.
[0139] The controller 92 and pixel controllers 94 can be made in
one or more integrated circuits having separate, independent, and
distinct substrates. For example, the pixel controllers 94 can be
chiplets, small, unpackaged integrated circuits such as unpackaged
dies interconnected with wires connected to contact pads on the
chiplets. The chiplets can be disposed on an independent
light-emitter substrate, such as a pixel substrate 84 or a display
substrate 80. If the chiplets are disposed on pixel substrates 84,
the pixel substrates 84 can be disposed on the display substrate
80. In an embodiment, the chiplets are made on a semiconductor
wafer and have a semiconductor substrate and the display substrate
80 is or includes glass, resin, polymer, plastic, or metal. The
pixel substrates 84 can be made in semiconductor materials or in
glass, resin, polymer, plastic, or metal. Semiconductor materials
(for example silicon) and processes for making small integrated
circuits are well known in the integrated circuit arts. Likewise,
display substrates 80 (destination substrates) and means for
interconnecting integrated circuit elements on the display
substrate 80 are well known in the printed circuit board arts. The
chiplets can be applied to the pixel substrates 84 or to the
display substrate 80 using micro transfer printing. The pixel
substrates 84 can be applied to the display substrate 80 using
micro transfer printing.
[0140] In one method of the present invention the pixel substrates
84 are disposed on the display substrate 80 by micro transfer
printing using compound micro assembly structures and methods, for
example as described in U.S. patent application Ser. No.
14/822,868, filed Aug. 10, 2015, entitled Compound Micro-Assembly
Strategies and Devices, which is hereby incorporated by reference
in its entirety. However, since the pixel substrates 84 are larger
than the chiplets, in another method of the present invention, the
pixel substrates 84 are disposed on the display substrate 80 using
pick-and-place methods found in the printed-circuit board industry,
for example using vacuum grippers. The OLED structures 10 or pixel
controllers 94 on the pixel substrates 84 can be interconnected
using photolithographic methods and materials or on the display
substrate 80 using printed circuit board methods and materials.
[0141] In useful embodiments the display substrate 80 includes
material, for example glass or plastic, different from a material
in an integrated-circuit or chiplet substrate, for example a
semiconductor material such as silicon. The pixel controllers 94
can be formed separately on separate semiconductor substrates,
assembled onto the pixel substrates 84, and then the assembled unit
is disposed on the surface of the display substrate 80. This
arrangement has the advantage that the OLED structure 10 can be
separately tested on the pixel substrates 84 and the pixel
substrate 84 accepted, repaired, or discarded before it is located
on the display substrate 80, thus improving yields and reducing
costs.
[0142] The OLED structures 10 are electrically connected to one or
more electrically conductive wires 98, 99 that electrically connect
the OLED structures 10 and the pixel controllers 94 or controllers
92 to conduct power, a ground reference voltage, or signals for
controlling the OLED structures 10. In an embodiment, the wires 96
are connected to a controller 92 that is external to the display
substrate 80. In an alternative embodiment, not shown, the
controller 92 is located on the display substrate 80 outside a
display area including the OLED structures 10. If individual pixel
controllers 94 are used, they can be spatially distributed over the
display substrate 80 in spatial correspondence to the pixels 90 or
on pixel substrates 84 that are spatially distributed over the
display substrate 80. The controller 92 controls the OLED
structures 10 or pixel controllers 92 by, for example, providing
power, a ground reference signal, and control signals.
[0143] In an embodiment, the OLED structures 10 are transfer
printed to the pixel substrates 84 or to the display substrate 80
in one or more transfers. For a discussion of micro-transfer
printing techniques see, U.S. Pat. Nos. 8,722,458, 7,622,367 and
8,506,867, each of which is hereby incorporated by reference. The
transferred OLED structures 10 are then interconnected, for example
with conductive wires and optionally including connection pads and
other electrical connection structures, to enable the controller 92
or pixel controllers 94 to electrically interact with the OLED
structures 10 to emit light. In an alternative process, the
transfer of the OLED structures 10 is performed before or after all
of the first and second electrical conductors 98, 99 are in place.
Thus, in embodiments the construction of the first and second
electrical conductors 98, 99 can be performed before the OLED
structures 10 are printed, or after the OLED structures 10 are
printed, or both. In an embodiment, the controller 92 is externally
located (for example on a separate printed circuit board substrate)
and electrically connected to the conductive wires using
connectors, ribbon cables, or the like. Alternatively, the
controller 92 is affixed to the display substrate 80 outside the
area on the display substrate 80 in which the OLED structures 10
are located and electrically connected to the first and second
electrical conductors 98, 99 using wires and buses 96, for example
using surface mount and soldering technology.
[0144] According to various embodiments of the present invention,
the micro-transfer-printed OLED display 82 can include a display
substrate 80 on which the OLED structures 10 are disposed. The
display substrate 80 usefully has two opposing smooth sides
suitable for material deposition, photolithographic processing, or
micro-transfer printing of OLED structures 10. The display
substrate 80 can have the size of a conventional display, for
example a rectangle with a diagonal of a few centimeters to one or
more meters. Such substrates are commercially available. The
display substrate 80 can include polymer, plastic, resin,
polyimide, PEN, PET, metal, metal foil, glass, a semiconductor, or
sapphire and have a transparency greater than or equal to 50%, 80%,
90%, or 95% for visible light. In some embodiments of the present
invention, the OLED structures 10 emit light through the display
substrate 80. In other embodiments, the OLED structures 10 emit
light in a direction opposite the display substrate 80. The display
substrate 80 can have a thickness from 5 to 10 microns, 10 to 50
microns, 50 to 100 microns, 100 to 200 microns, 200 to 500 microns,
500 microns to 0.5 mm, 0.5 to 1 mm, 1 mm to 5 mm, 5 mm to 10 mm, or
10 mm to 20 mm. According to embodiments of the present invention,
the display substrate 80 can include layers formed on an underlying
structure or substrate, for example a rigid or flexible glass or
plastic substrate. In an embodiment of the present invention, the
OLED structures 10 have light-emissive areas of less than 1600
square microns, less than or equal to 800 square microns, less than
or equal to 400 square microns, less than or equal to 200 square
microns, less than or equal to 100 square microns, or less than or
equal to 50 square microns. In other embodiments, the OLED
structures 10 have physical dimensions that are less than 100
.mu.m, for example having a width from 5 to 10 .mu.m, 10 to 20
.mu.m, or 20 to 50 .mu.m, having a length from 5 to 10 .mu.m, 10 to
20 .mu.m, or 20 to 50 .mu.m, or having a height from 2 to 5 .mu.m,
4 to 10 .mu.m, 10 to 20 .mu.m, or 20 to 50 .mu.m. The OLED
structures 10 can provide highly saturated display colors and a
substantially Lambertian emission providing a wide viewing
angle.
[0145] According to various embodiments, the micro-transfer-printed
OLED display 82 of the present invention, includes a variety of
designs having a variety of resolutions, OLED structure 10 sizes,
and displays having a range of display areas. For example, display
areas ranging from 1 cm by 1 cm to 10 m by 10 m in size are
contemplated. The resolution of OLED structures 10 over a display
area can also vary, for example from OLED structures 10 per inch to
hundreds of light emitters per inch. Thus, the present invention
has application in both low-resolution and very high-resolution
displays and from very small to very large displays.
[0146] As shown in FIGS. 1, 3, and 6, the full-color pixels 90 form
a regular array on the display substrate 80. Alternatively, at
least some of the full-color pixels 90 have an irregular
arrangement on the display substrate 80.
[0147] In an embodiment, the integrated circuits or chiplets are
formed in substrates or on supports separate from the display
substrate 80. For example, the OLED structures 10 are separately
formed in a semiconductor source wafer. The OLED structures 10 are
then removed from the source wafer and transferred, for example
using micro transfer printing, to the display substrate 80 or pixel
substrate 84.
[0148] By employing a multi-step transfer or assembly process,
increased yields are achieved and thus reduced costs for the
micro-transfer-printed OLED display 82 of the present invention.
Additional details useful in understanding and performing aspects
of the present invention are described in U.S. patent application
Ser. No. 14/743,981, filed Jun. 18, 2015, entitled Micro-Assembled
Micro LED Displays and Lighting Elements, which is hereby
incorporated by reference in its entirety.
[0149] As is understood by those skilled in the art, the terms
"over", "under", "above", "below", "beneath", and "on" are relative
terms and can be interchanged in reference to different
orientations of the layers, elements, and substrates included in
the present invention. For example, a first layer on a second
layer, in some embodiments means a first layer directly on and in
contact with a second layer. In other embodiments, a first layer on
a second layer can include another layer there between.
Additionally, "on" can mean "on" or "in." As additional
non-limiting examples, a sacrificial layer is considered "on" a
substrate when a layer of sacrificial material is on top of the
substrate, when a portion of the substrate itself is the
sacrificial layer, or when the sacrificial layer comprises material
on top of the substrate and a portion of the substrate itself.
[0150] Having described certain embodiments, it will now become
apparent to one of skill in the art that other embodiments
incorporating the concepts of the disclosure may be used.
Therefore, the invention should not be limited to the described
embodiments, but rather should be limited only by the spirit and
scope of the following claims.
[0151] Throughout the description, where apparatus and systems are
described as having, including, or comprising specific components,
or where processes and methods are described as having, including,
or comprising specific steps, it is contemplated that,
additionally, there are apparatus, and systems of the disclosed
technology that consist essentially of, or consist of, the recited
components, and that there are processes and methods according to
the disclosed technology that consist essentially of, or consist
of, the recited processing steps.
[0152] It should be understood that the order of steps or order for
performing certain action is immaterial so long as the disclosed
technology remains operable. Moreover, two or more steps or actions
in some circumstances can be conducted simultaneously. The
invention has been described in detail with particular reference to
certain embodiments thereof, but it will be understood that
variations and modifications can be effected within the spirit and
scope of the invention.
PARTS LIST
[0153] 10 organic light-emitting diode structure [0154] 10R red
organic light-emitting diode structure [0155] 10G green organic
light-emitting diode structure [0156] 10B blue organic
light-emitting diode structure [0157] 12 tether [0158] 14 anchor
[0159] 16 pixel component [0160] 18 sacrificial layer [0161] 20
source substrate [0162] 20R red source substrate [0163] 20G green
source substrate [0164] 20B blue source substrate [0165] 30
transparent insulator [0166] 32 insulator [0167] 34 bank insulator
[0168] 40 transparent electrode [0169] 50 first electrode portion
[0170] 52 second electrode [0171] 53 first protrusion [0172] 54
second protrusion [0173] 55 first electrode [0174] 56 second layer
of second electrode [0175] 60 organic material layer(s) [0176] 65
organic light-emitting diode [0177] 70 patterned protective layer
[0178] 71 barrier material [0179] 72 third conductive layer [0180]
80 destination substrate/display substrate [0181] 82
micro-transfer-printed OLED display [0182] 84 pixel substrate
[0183] 90 pixel [0184] 92 controller [0185] 94 pixel controller
[0186] 96 wires/bus [0187] 98 first electrical conductor [0188] 99
second electrical conductor [0189] 100 provide source substrate
step [0190] 100R provide red source substrate step [0191] 100G
provide green source substrate step [0192] 100B provide blue source
substrate step [0193] 101 form first electrode structure step
[0194] 103 form second electrode structure step [0195] 105 provide
destination substrate step [0196] 110 pattern first electrode step
[0197] 120 pattern transparent dielectric step [0198] 130 pattern
transparent electrode step [0199] 140 pattern bank insulator step
[0200] 150 pattern OLED layers step [0201] 150R pattern red OLED
layers step [0202] 150G pattern green OLED layers step [0203] 150B
pattern blue OLED layers step [0204] 160 pattern second electrode
step [0205] 170 pattern dielectric step [0206] 180 etch sacrificial
layer step [0207] 190R micro transfer print red OLED structure step
[0208] 190G micro transfer print green OLED structure step [0209]
190B micro transfer print blue OLED structure step
* * * * *