U.S. patent application number 11/589792 was filed with the patent office on 2010-05-13 for organic electronic device.
Invention is credited to Hyeon Choi, Min Soo Kang, Se Hwan Son.
Application Number | 20100117063 11/589792 |
Document ID | / |
Family ID | 38002848 |
Filed Date | 2010-05-13 |
United States Patent
Application |
20100117063 |
Kind Code |
A9 |
Kang; Min Soo ; et
al. |
May 13, 2010 |
Organic electronic device
Abstract
Disclosed is an electronic device including an n-type organic
compound layer as a portion of an electrode for hole injection or
hole extraction. The electronic device includes a first electrode
including a conductive layer and an n-type organic compound layer
disposed on the conductive layer; a second electrode; and a p-type
organic compound layer that is interposed between the n-type
organic compound layer of the first electrode and the second
electrode and forms an NP junction together with the n-type organic
compound layer of the first electrode and energy levels of the
layers satisfy the following Expressions (1) and (2): 2
eV<E.sub.nL-E.sub.F1.ltoreq.4 eV (1) E.sub.pH-E.sub.nL.ltoreq.1
eV (2) where E.sub.F1 is a Fermi energy level of the conductive
layer of the first electrode, E.sub.nL is an LUMO energy level of
the n-type organic compound layer of the first electrode, and
E.sub.pH is an HOMO energy level of the p-type organic compound
layer forming the NP junction together with the n-type organic
compound layer of the first electrode.
Inventors: |
Kang; Min Soo; (Daejeon
Metropolitan City, KR) ; Son; Se Hwan; (Daejeon
Metropolitan City, KR) ; Choi; Hyeon; (Daejeon
Metropolitan City, KR) |
Correspondence
Address: |
MCKENNA LONG & ALDRIDGE LLP
1900 K STREET, NW
WASHINGTON
DC
20006
US
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20070102698 A1 |
May 10, 2007 |
|
|
Family ID: |
38002848 |
Appl. No.: |
11/589792 |
Filed: |
October 31, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
10798584 |
Mar 10, 2004 |
7538341 |
|
|
11589792 |
Oct 31, 2006 |
|
|
|
09914731 |
Aug 30, 2001 |
6720573 |
|
|
PCT/KR00/01537 |
Dec 27, 2000 |
|
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|
10798584 |
Mar 10, 2004 |
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Current U.S.
Class: |
257/40 |
Current CPC
Class: |
H01L 51/5218 20130101;
Y02E 10/549 20130101; H01L 51/5278 20130101; H01L 51/5004 20130101;
H01L 51/0072 20130101; H01L 51/5012 20130101; H01L 51/5206
20130101; H01L 51/52 20130101; H01L 51/0058 20130101; H01L 51/5088
20130101; H01L 27/3204 20130101; Y02P 70/521 20151101; Y02P 70/50
20151101 |
Class at
Publication: |
257/040 |
International
Class: |
H01L 29/08 20060101
H01L029/08 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 1, 2005 |
KR |
2005-0103664 |
Dec 31, 1999 |
KR |
1999-067746 |
Dec 26, 2000 |
KR |
2000-82085 |
Claims
1. An electronic device, comprising: a first electrode including a
conductive layer and an n-type organic compound layer disposed on
the conductive layer; a second electrode; and a p-type organic
compound layer that is interposed between the n-type organic
compound layer of the first electrode and the second electrode and
forms an NP junction together with the n-type organic compound
layer of the first electrode, wherein energy levels of the layers
satisfy the following Expressions (1) and (2): 2
eV<E.sub.nL-E.sub.F1.ltoreq.4 eV (1) E.sub.pH-E.sub.nL.ltoreq.1
eV (2) where E.sub.F1 is a Fermi energy level of the conductive
layer of the first electrode, E.sub.nL is an LUMO energy level of
the n-type organic compound layer of the first electrode, and
E.sub.pH is an HOMO energy level of the p-type organic compound
layer forming the NP junction together with the n-type organic
compound layer of the first electrode.
2. The electronic device as set forth in claim 1, further
comprising: at least one organic compound layer disposed between
the p-type organic compound layer and the second electrode.
3. The electronic device as set forth in claim 1, wherein the
n-type organic compound layer of the first electrode contains a
compound represented by the following Formula 1: ##STR5## where
each of R.sup.1 to R.sup.6 is selected from a group consisting of
hydrogen, halogen atoms, nitrile (--CN), nitro (--NO.sub.2),
sulfonyl (--SO.sub.2R), sulfoxide (--SOR), sulfonamide
(--SO.sub.2NR), sulfonate (--SO.sub.3R), trifluoromethyl
(--CF.sub.3), ester (--COOR), amide (--CONHR or --CONRR'),
substituted or unsubstituted straight or branched chain
C.sub.1-C.sub.12 alkoxy, substituted or unsubstituted straight or
branched C.sub.1-C.sub.12 alkyl, substituted or unsubstituted
aromatic or non-aromatic heterocyclic rings, substituted or
unsubstituted aryl, substituted or unsubstituted mono- or
di-arylamine, and substituted or unsubstituted aralkylamine, and
each of R and R' are selected from a group consisting of
substituted or unsubstituted C.sub.1-C.sub.60 alkyl, substituted or
unsubstituted aryl, and substituted or unsubstituted 5-7 membered
heterocyclic rings.
4. The electronic device as set forth in claim 3, wherein the
compound of Formula 1 is selected from compounds represented by the
following Formulae 1-1 to 1-6: ##STR6## ##STR7##
5. The electronic device as set forth in claim 1, wherein the
n-type organic compound layer of the first electrode contains
2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ),
fluoro-substituted 3,4,9,10-perylenetetracarboxylic dianhydride
(PTCDA), cyano-substituted 3,4,9,10-perylenetetracarboxylic
dianhydride (PTCDA), naphthalene-tetracaboxylic-dianhydride
(NTCDA), fluoro-substituted naphthalene-tetracaboxylic-dianhydride
(NTCDA), or cyano-substituted
naphthalene-tetracaboxylic-dianhydride (NTCDA).
6. The electronic device as set forth in claim 1, wherein the
conductive layer of the first electrode is formed of a material
selected from a group of a metal, a metal oxide, and a conductive
polymer.
7. The electronic device as set forth in claim 1, wherein the
conductive layer of the first electrode and the second electrode
are formed of the same material.
8. The electronic device as set forth in claim 1, wherein the
conductive layer of the first electrode and the second electrode
are formed of a material selected from a group consisting of Ca,
Ca--Ag, Ca--IZO, and Mg--Ag.
9. The electronic device as set forth in claim 1, wherein the
electronic device is an organic light emitting device that
includes: an anode including a conductive layer and an n-type
organic compound layer disposed on the conductive layer; a cathode;
and a p-type organic compound layer that is interposed between the
n-type organic compound layer of the anode and the cathode and
forms an NP junction together with the n-type organic compound
layer of the anode, wherein energy levels of the layers satisfy the
following Expressions (3) and (4): 2
eV<E.sub.nL-E.sub.F1.ltoreq.4 eV (3) E.sub.pH-E.sub.nL.ltoreq.1
eV (4) where E.sub.F1 is a Fermi energy level of the conductive
layer of the anode, E.sub.nL is an LUMO energy level of the n-type
organic compound layer of the anode, and E.sub.pH is an HOMO energy
level of the p-type organic compound layer forming the NP junction
together with the n-type organic compound layer of the anode.
10. The electronic device as set forth in claim 9, further
comprising: at least one selected from a hole injection layer, a
hole transport layer, an emitting layer, an electron transport
layer, and an electron injection layer, which is disposed between
the p-type organic compound layer and the cathode.
11. The electronic device as set forth in claim 9, wherein the
conductive layer of the anode and the cathode are formed of the
same material.
12. The electronic device as set forth in claim 9, wherein the
conductive layer of the anode and the cathode are formed of a
material selected from a group consisting of Ca, Ca--Ag, Ag--IZO,
and Ma--Ag.
13. The electronic device as set forth in claim 9, wherein the
n-type organic compound layer of the anode has an LUMO energy level
of 4 to 7 eV and electron mobility of 10.sup.-8 cm.sup.2/Vs to 1
cm.sup.2/Vs.
14. The electronic device as set forth in claim 9, wherein the
n-type organic compound layer of the anode contains a compound
represented by the following Formula 1: ##STR8## where each of
R.sup.1 to R.sup.6 is selected from a group consisting of hydrogen,
halogen atoms, nitrile (--CN), nitro (--NO.sub.2), sulfonyl
(--SO.sub.2R), sulfoxide (--SOR), sulfonamide (--SO.sub.2NR),
sulfonate (--SO.sub.3R), trifluoromethyl (--CF.sub.3), ester
(--COOR), amide (--CONHR or --CONRR'), substituted or unsubstituted
straight or branched chain C.sub.1-C.sub.12 alkoxy, substituted or
unsubstituted straight or branched C.sub.1-C.sub.12 alkyl,
substituted or unsubstituted aromatic or non-aromatic heterocyclic
rings, substituted or unsubstituted aryl, substituted or
unsubstituted mono- or di-arylamine, and substituted or
unsubstituted aralkylamine, and each of R and R' are selected from
a group consisting of substituted or unsubstituted C.sub.1-C.sub.60
alkyl, substituted or unsubstituted aryl, and substituted or
unsubstituted 5-7 membered heterocyclic rings.
15. The electronic device as set forth in claim 14, wherein the
compound of Formula 1 is selected from compounds represented by the
following Formulae 1-1 to 1-6: ##STR9## ##STR10##
16. The electronic device as set forth in claim 9, wherein the
n-type organic compound layer of the anode contains
2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ),
fluoro-substituted 3,4,9,10-perylenetetracarboxylic dianhydride
(PTCDA), cyano-substituted 3,4,9,10-perylenetetracarboxylic
dianhydride (PTCDA), naphthalene-tetracaboxylic-dianhydride
(NTCDA), fluoro-substituted naphthalene-tetracaboxylic-dianhydride
(NTCDA), or cyano-substituted
naphthalene-tetracaboxylic-dianhydride (NTCDA).
17. The electronic device as set forth in claim 1, wherein the
electronic device is an organic solar cell that includes: an anode
including a conductive layer and an n-type organic compound layer
disposed on the conductive layer; a cathode; and an electron donor
layer consisting of a p-type organic compound layer that is
interposed between the n-type organic compound layer of the anode
and the cathode and forms an NP junction together with the n-type
organic compound layer of the anode, wherein energy levels of the
layers satisfy the following Expressions (5) and (6): 2
eV<E.sub.nL-E.sub.F1.ltoreq.4 eV (5) E.sub.pH-E.sub.nL.ltoreq.1
eV (6) where E.sub.F1 is a Fermi energy level of the conductive
layer of the anode, E.sub.nL is an LUMO energy level of the n-type
organic compound layer of the anode, and E.sub.pH is an HOMO energy
level of the p-type organic compound layer forming the NP junction
together with the n-type organic compound layer of the anode.
18. The electronic device as set forth in claim 17, further
comprising: an electron acceptor layer disposed between the cathode
and the electron donor layer.
19. The electronic device as set forth in claim 17, wherein the
conductive layer of the anode and the cathode are formed of the
same material.
20. The electronic device as set forth in claim 17, wherein the
n-type organic compound layer of the anode contains
2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ),
fluoro-substituted 3,4,9,10-perylenetetracarboxylic dianhydride
(PTCDA), cyano-substituted 3,4,9,10-perylenetetracarboxylic
dianhydride (PTCDA), naphthalene-tetracaboxylic-dianhydride
(NTCDA), fluoro-substituted naphthalene-tetracaboxylic-dianhydride
(NTCDA), cyano-substituted naphthalene-tetracaboxylic-dianhydride
(NTCDA), or hexanitrile hexaazatriphenylene (HAT).
21. The electronic device as set forth in claim 1, wherein the
electronic device is an organic transistor that includes: a source
electrode; a drain electrode; a gate electrode; an insulating layer
disposed on the gate electrode; and a p-type organic compound layer
disposed on the insulating layer, and at least one of the source
electrode and the drain electrode includes a conductive layer and
an n-type organic compound layer forming an NP junction together
with the p-type organic compound layer, wherein energy levels of
the layers satisfy the following Expressions (7) and (8): 2
eV<E.sub.nL-E.sub.F1.ltoreq.4 eV (7) E.sub.pH-E.sub.nL.ltoreq.1
eV (8) where E.sub.F1 is a Fermi energy level of the conductive
layer of the source electrode or drain electrode, E.sub.nL is an
LUMO energy level of the n-type organic compound layer of the
source electrode or drain electrode, and E.sub.pH is an HOMO energy
level of the p-type organic compound layer forming the NP junction
together with the n-type organic compound layer of the source
electrode or drain electrode.
22. The electronic device as set forth in claim 21, wherein the
n-type organic compound layer contains
2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ),
fluoro-substituted 3,4,9,10-perylenetetracarboxylic dianhydride
(PTCDA), cyano-substituted 3,4,9,10-perylenetetracarboxylic
dianhydride (PTCDA), naphthalene-tetracaboxylic-dianhydride
(NTCDA), fluoro-substituted naphthalene-tetracaboxylic-dianhydride
(NTCDA), cyano-substituted naphthalene-tetracaboxylic-dianhydride
(NTCDA), or hexanitrile hexaazatriphenylene (HAT).
23. A stack-type organic light emitting device comprising at least
two electronic device as set forth in claim 9, wherein an anode of
one electronic device is connected to a cathode of an adjacent
electronic device in series.
24. The stack-type organic light emitting device as set forth in
claim 23, wherein the conductive layer of the anode and the cathode
of the electronic device are formed of the same material.
25. The stack-type organic light emitting device as set forth in
claim 24, in the anode and the cathode deposed in the interface
between the electronic devices connected in series, the conductive
layer of the anode and the cathode form a single conductive layer.
Description
TECHNICAL FIELD
[0001] The present invention relates to an electronic device in
which an electrode for hole injection or hole extraction has an
n-type organic compound layer. More specifically, the present
invention relates to an electronic device capable of reducing an
energy barrier for hole injection or hole extraction.
[0002] This application claims priority benefits from Korean Patent
Application No. 10-2005-0103664, filed on Nov. 1, 2005, the entire
contents of which are fully incorporated herein by reference.
BACKGROUND ART
[0003] In general, an electronic device, such as a solar cell, an
organic light emitting device, or an organic transistor, includes
two electrodes and an organic compound layer interposed
therebetween. For example, a solar cell generates electricity using
electrons and holes separated from exitons that are generated in an
organic compound layer by solar energy. An organic light emitting
device converts a current into visible light by injecting electrons
and holes from two electrodes into an organic compound layer. An
organic transistor transports holes or electrons generated in an
organic compound layer between a source electrode and a drain
electrode by applying a voltage to a gate electrode. The electronic
device may further include an electron/hole injection layer, an
electron/hole extraction layer, or an electron/hole transport
layer.
[0004] However, since the interfaces between the organic compound
layer and the electrodes each containing a metal, a metal oxide, or
a conductive polymer are unstable, heat from the outside, heat
generated inside, or an electric field applied to the electronic
device may have a bad effect on performance of the electronic
device. Further, due to a conductive energy level difference
between the organic compound layer and the electron/hole injection
layer, the electron/hole extraction layer, or the electron/hole
transport layer, a driving voltage for driving the electronic
device may increase. Therefore, it is important not only to
minimize the energy barrier for hole/electron injection to the
electrodes and hole/electron extraction from the electrodes, but
also to stabilize the interfaces between the organic compound layer
and the electrodes and the interfaces between the organic compound
and the electron/hole injection layer, the electron/hole extraction
layer, and the electron/hole transport layer.
[0005] Electronic devices capable of adjusting the energy level
differences between the electrodes and the organic compound layer
interposed therebetween have been developed. In case of an organic
light emitting device, in order to smoothly inject holes, an anode
is adjusted to have a Fermi energy level similar to an HOMO
(highest occupied molecular orbital) energy level of a hole
injection layer or a material having an HOMO energy level similar
to a Fermi energy level of an anode is selected as a material for a
hole injection layer. However, since the hole injection layer
should be selected in view of an HOMO energy level of a hole
transport layer or an emitting layer close to the hole injection
layer as well as in view of the Fermi energy level of the anode,
there is a limitation to select a material for the hole injection
layer.
[0006] For this reason, in general, a method of adjusting a Fermi
energy level of an anode is used to manufacture an organic light
emitting device. However, in such a method, a material for the
anode is limited. In an organic transistor, gold or precious metals
are used as materials of a source electrode and a drain electrode.
However, precious metals, such as gold, are very expensive and are
not easily processed compared with other metals. Therefore, the
manufacturing process of the organic transistor is complicated and
thus it is difficult to commercially use the organic
transistor.
DISCLOSURE
Technical Problem
[0007] Accordingly, it is an object of the present invention to
provide an electronic device, such as an organic light emitting
device, an organic solar cell and an organic transistor, which
includes a first electrode, a second electrode, and an organic
compound layer interposed between the first and second electrodes,
in which the first electrode and the second electrode are formed of
the same material, and a stack-type organic light emitting device
using the organic light emitting device as a repetition unit.
[0008] It is another object of the present invention to provide an
electronic device, such as an organic light emitting device, an
organic solar cell, and an organic transistor, in which, in a case
where a first electrode includes an n-type organic compound layer
and a conductive layer, even though an energy difference between an
LUMO (Lowest Unoccupied Molecular Orbital) energy level of the
n-type organic compound layer of the first electrode and a Fermi
energy level of the conductive layer of the first electrode is
large, for example, 2 eV to 4 eV, hole injection and/or hole
extraction capacity can be improved with a low electrical barrier
for hole injection and/or hole extraction at an interface between
an electrode and an organic compound layer, whereby excellent
device performance exhibits, and in which an electrode can be
formed of various materials, whereby a device manufacturing process
can be simplified.
TECHNICAL SOLUTION
[0009] According to an exemplary embodiment of the invention, an
electronic device includes a first electrode including a conductive
layer and an n-type organic compound layer disposed on the
conductive layer; a second electrode; and a p-type organic compound
layer that is interposed between the n-type organic compound layer
of the first electrode and the second electrode and forms an NP
junction together with the n-type organic compound layer of the
first electrode. Energy levels of the layers satisfy the following
Expressions (1) and (2): 2 eV<E.sub.nL-E.sub.F1.ltoreq.4 eV (1)
E.sub.pH-E.sub.nL.ltoreq.1 eV (2)
[0010] where E.sub.F1 is a Fermi energy level of the conductive
layer of the first electrode, E.sub.nL is an LUMO energy level of
the n-type organic compound layer of the first electrode, and
E.sub.pH is an HOMO energy level of the p-type organic compound
layer forming the NP junction together with the n-type organic
compound layer of the first electrode.
[0011] According to another exemplary embodiment of the invention,
an organic light emitting device includes an anode including a
conductive layer and an n-type organic compound layer disposed on
the conductive layer; a cathode; and a p-type organic compound
layer that is interposed between the n-type organic compound layer
of the anode and the cathode and forms an NP junction together with
the n-type organic compound layer of the anode. Energy levels of
the layers satisfy the following Expressions (3) and (4): 2
eV<E.sub.nL-E.sub.F1.ltoreq.4 eV (3) E.sub.pH-E.sub.nL.ltoreq.1
eV (4)
[0012] where E.sub.F1 is a Fermi energy level of the conductive
layer of the anode, E.sub.nL is an LUMO energy level of the n-type
organic compound layer of the anode, and E.sub.pH is an HOMO energy
level of the p-type organic compound layer forming the NP junction
together with the n-type organic compound layer of the anode.
[0013] According to another exemplary embodiment of the invention,
an organic solar cell includes an anode including a conductive
layer and an n-type organic compound layer disposed on the
conductive layer; a cathode; and an electron donor layer consisting
of a p-type organic compound layer that is interposed between the
n-type organic compound layer of the anode and the cathode and
forms an NP junction together with the n-type organic compound
layer of the anode. Energy levels of the layers satisfy the
following Expressions (5) and (6): 2
eV<E.sub.nL-E.sub.F1.ltoreq.4 eV (5) E.sub.pH-E.sub.nL.ltoreq.1
eV (6)
[0014] where E.sub.F1 is a Fermi energy level of the conductive
layer of the anode, E.sub.nL is an LUMO energy level of the n-type
organic compound layer of the anode, and E.sub.pH is an HOMO energy
level of the p-type organic compound layer forming the NP junction
together with the n-type organic compound layer of the anode.
[0015] According to another exemplary embodiment of the invention,
an organic transistor includes a source electrode; a drain
electrode; a gate electrode; an insulating layer disposed on the
gate electrode; and a p-type organic compound layer disposed on the
insulating layer. At least one of the source electrode and the
drain electrode includes a conductive layer and an n-type organic
compound layer forming an NP junction together with the p-type
organic compound layer, and energy levels of the layers satisfy the
following Expressions (7) and (8): 2
eV<E.sub.nL-E.sub.F1.ltoreq.4 eV (7) E.sub.pH-E.sub.nL.ltoreq.1
eV (8)
[0016] where E.sub.F1 is a Fermi energy level of the conductive
layer of the source electrode or drain electrode, E.sub.nL is an
LUMO energy level of the n-type organic compound layer of the
source electrode or drain electrode, and E.sub.pH is an HOMO energy
level of the p-type organic compound layer forming the NP junction
together with the n-type organic compound layer of the source
electrode or drain electrode.
ADVANTAGEOUS EFFECTS
[0017] As described above, in an electronic device, such as an
organic light emitting device, a stack-type light emitting device,
an organic transistor, and an organic solar cell, according to the
invention, a conductive layer of a first electrode and a second
electrode may be formed of the same material. Therefore, it is
possible to obtain a high-luminance organic light emitting device
having a stacked structure and to realize various devices, such as
a stack-type electronic device in which a plurality of unit
electronic devices are stacked. Further, it is possible to use
various electrode materials in an electronic device, such as an
organic light emitting device, an organic transistor, and an
organic solar cell, requiring hole injection and hole extraction
layers, and to simplify the manufacturing process.
[0018] Furthermore, since an organic electronic device according to
the invention lowers an electrical barrier for hole injection or
hole extraction and forms an NP junction of an n-type organic
compound layer and a p-type organic compound layer, the efficiency
of the device is high. In addition, since various materials can be
used to form an electrode, it is possible to further simplify the
manufacturing process.
DESCRIPTION OF DRAWINGS
[0019] FIGS. 1(a) and 1(b) are views illustrating energy levels of
a first electrode for hole injection or hole extraction before and
after applying an n-type organic compound layer to the first
electrode in an electronic device according to an exemplary
embodiment of the invention, respectively.
[0020] FIG. 2 is a view illustrating an NP junction formed between
an n-type organic compound layer of a first electrode for hole
injection or hole extraction and a p-type organic compound layer in
an electronic device according to an exemplary embodiment of the
invention.
[0021] FIGS. 3 to 5 are cross-sectional views schematically
illustrating organic light emitting devices according to exemplary
embodiments of the invention;
[0022] FIG. 6 is a view illustrating an ideal energy level of a
conventional organic light emitting device.
[0023] FIG. 7 is a view illustrating an energy level of an organic
light emitting device according to an exemplary embodiment of the
invention.
[0024] FIG. 8 is a cross-sectional view schematically illustrating
an organic solar cell according to an exemplary embodiment of the
invention.
[0025] FIG. 9 is a cross-sectional view schematically illustrating
an organic transistor according to an exemplary embodiment of the
invention.
[0026] FIGS. 10 and 11 are cross-sectional views schematically
illustrating stack-type organic light emitting devices according to
exemplary embodiments of the invention.
REFERENCE NUMERALS
[0027] 31, 41, 61: SUBSTRATE [0028] 32, 42: ANODE [0029] 37, 45:
CATHODE [0030] 33: HOLE INJECTION LAYER [0031] 34: HOLE TRANSPORT
LAYER [0032] 35: EMITTING LAYER [0033] 36: ELECTRON TRANSPORT LAYER
[0034] 43: ELECTRON DONER LAYER [0035] 44: ELECTRON ACCEPTOR LAYER
[0036] 62: GATE ELECTRODE [0037] 63: INSULATING LAYER [0038] 64:
p-TYPE ORGANIC COMPOUND LAYER [0039] 65: SOURCE ELECTRODE [0040]
66: DRAIN ELECTRODE [0041] 32a, 42a, 65a, 66a: CONDUCTIVE LAYER
[0042] 32b, 42b, 67: n-TYPE ORGANIC COMPOUND LAYER
BEST MODE
[0043] Hereinafter, only preferred embodiments of the invention
will be illustrated and described by explaining conditions
contrived by the inventors in order to implement the present
invention. However, various changes or modifications can be made
without departing from the scope of the present invention. The
accompanying drawings and the following detailed description are
illustrative but not intended to limit the invention.
[0044] An electronic device according to an exemplary embodiment of
the invention includes a first electrode including a conductive
layer and an organic compound layer that is formed on the
conductive layer and has n-type semiconductor features
(hereinafter, referred to as an "n-type organic compound layer"), a
second electrode, and an organic compound layer having p-type
semiconductor features for forming an NP junction together with the
n-type organic compound layer of the first electrode (hereinafter,
referred to as a "p-type organic compound layer"). The electronic
device may further include at least one selected from an
electron/hole injection layer, an electron/hole extraction layer,
an electron/hole transport layer, and an emitting layer, which is
disposed between the p-type organic compound layer and the second
electrode.
[0045] The conductive layer of the first electrode may be formed of
a metal, a metal oxide, or a conductive polymer. The conductive
polymer may include an electro-conductive polymer. The n-type
organic compound layer formed on the conductive layer of the first
electrode has a predetermined LUMO energy level with respect to a
Fermi energy level of the conductive layer and an HOMO energy level
of the p-type organic compound layer. The n-type organic compound
layer of the first electrode is selected so as to reduce an energy
difference between the LUMO energy level of the n-type organic
compound layer of the first electrode and the Fermi energy level of
the conductive layer of the first electrode and an energy
difference between the LUMO energy level of the n-type organic
compound layer of the first electrode and the HOMO energy level of
the p-type organic compound layer. Therefore, holes are easily
injected into the HOMO energy level of the p-type organic compound
layer through the LUMO energy level of the n-type organic compound
layer of the first electrode. Also, holes are easily extracted from
the HOMO energy level of the p-type organic compound layer through
the LUMO energy level of the n-type organic compound layer of the
first electrode. However, in the invention, the energy difference
between the LUMO energy level of the n-type organic compound layer
of the first electrode and the Fermi energy level of the conductive
layer of the first electrode is equal to or more than a
predetermined value such that the conductive layer of the first
electrode is formed of a material having a low work function.
Specifically, in the invention, various materials can be used to
form the electrode. The detailed description thereof will be
described below.
[0046] International Application No. PCT/KR2005/001381 in the name
of the inventors discloses an electrode device that includes a
first electrode including a conductive layer and an n-type organic
compound layer disposed on the conductive layer; a second
electrode; and a p-type organic compound layer that is interposed
between the n-type organic compound layer of the first electrode
and the second electrode and forms an NP junction together with the
n-type organic compound layer, wherein a difference between an LUMO
energy level of the n-type organic compound layer of the first
electrode and a Fermi energy level of the conductive layer of the
first electrode is 2 eV or less, and a difference between the LUMO
energy level of the n-type organic compound layer of the first
electrode and an HOMO energy level of the p-type organic compound
layer is 1 eV or less. In the electronic device according to the
above-mentioned application, hole injection and/or hole extraction
capacity can be improved with a low energy barrier for hole
injection and/or hole extraction at an interface between the first
electrode and the organic compound layer, whereby excellent device
performance exhibits, and an electrode can be formed of various
materials, whereby a device manufacturing process can be
simplified.
[0047] When the conductive layer of the first electrode and the
second electrode are formed of the same material, it is possible to
realize various devices, such as a stack-type electronic device in
which unit electronic devices are stacked and to simplify a device
manufacturing process. Nevertheless, in the electronic device
according to the above-mentioned application, in case of the second
electrode, unlike the first electrode, it is advantageous to use a
material having a low work function such that electrons are easily
injected thereto. For example, LiF--Al, Li--Al, Ca, Ca--Ag, or
Ca--IZO is used as the material of the second electrode. Therefore,
in a case where the first electrode should satisfy the
above-mentioned condition that the difference between the LUMO
energy level of the n-type organic compound layer of the first
electrode and the Fermi energy level of the conductive layer of the
first electrode is 2 eV or less, there is a limitation to apply Ca,
Ca--Ag, or Ca--IZO among the above-mentioned examples of the
material of the second electrode to the conductive layer of the
first electrode.
[0048] According to this invention, the energy difference between
the LUMO energy level of the n-type organic compound layer of the
first electrode and the Fermi energy level of the conductive layer
of the first electrode is more than 2 eV and equal to or less than
4 eV. Further, the energy difference between the LUMO energy level
of the n-type organic compound layer of the first electrode and the
HOMO energy level of the p-type organic compound layer is 1 eV or
less, and preferably, approximately 0.5 eV or less. This energy
difference is preferably approximately 0.01 eV to 1 eV in view of
material selection.
[0049] When the energy difference between the LUMO energy level of
the n-type organic compound layer of the first electrode and the
Fermi energy level of the conductive layer of the first electrode
is more than 4 eV, an effect of a surface dipole or a gap state on
an energy barrier for hole injection or hole extraction is reduced.
When the energy difference between the LUMO energy level of the
n-type organic compound layer of the first electrode and the Fermi
energy level of the conductive layer of the first electrode is
equal to or less than 2 eV, there is a limitation in the selection
of materials for the conductive layer of the first electrode. Also,
when the energy difference between the LUMO energy level of the
n-type organic compound layer of the first electrode and the HOMO
energy level of the p-type organic compound layer is more than
approximately 1 eV, the NP junction of the p-type organic compound
layer and the n-type organic compound layer of the first electrode
is not easily formed and thus a driving voltage for hole injection
or hole extraction increases.
[0050] FIGS. 1(a) and 1(b) illustrate energy levels of a first
electrode for hole injection or hole extraction before and after an
n-type organic compound layer is applied to the first electrode in
an electronic device according to an exemplary embodiment of the
invention, respectively. In FIG. 1(a), the conductive layer of the
first electrode has a Fermi energy level E.sub.F1 lower than a
Fermi energy level E.sub.F2 of the n-type organic compound layer. A
vacuum level (VL) represents an energy level at which electrons can
freely move in the conductive layer and the n-type organic compound
layer.
[0051] In a case where the electronic device uses the n-type
organic compound layer as a portion of the first electrode, the
conductive layer is brought into contact with the n-type organic
compound layer. In FIG. 1(b), since electrons move from the
conductive layer to the n-type organic compound layer, the Fermi
energy levels E.sub.F1 and E.sub.F2 of both layers come to be the
same. As a result, a surface dipole is formed at the interface of
the conductive layer and the n-type organic compound layer, and the
vacuum level, the Fermi energy level, the HOMO energy level, and
the LUMO energy level are changed as shown in FIG. 1(b).
[0052] Therefore, even though the energy difference between the
Fermi energy level of the conductive layer of the first electrode
and the LUMO energy level of the n-type organic compound layer of
the first electrode is large, the energy barrier for hole injection
or hole extraction can be reduced by bringing the conductive layer
into contact with the n-type organic compound layer. Further, when
the conductive layer has a Fermi energy level lower than the LUMO
energy level of the n-type organic compound layer, electrons move
from the conductive layer to the n-type organic compound layer, and
thus a gap state is formed at an interface between the conductive
layer and the n-type organic compound layer. As a result, the
energy barrier for electron transport is minimized.
[0053] The n-type organic compound layer formed on the conductive
layer of the first electrode may contain a compound represented by
the following Formula 1. ##STR1##
[0054] In Formula 1, each of R.sup.1 to R.sup.6 is selected from a
group consisting of hydrogen, halogen atoms, nitrile (--CN), nitro
(--NO.sub.2), sulfonyl (--SO.sub.2R), sulfoxide (--SOR),
sulfonamide (--SO.sub.2NR), sulfonate (--SO.sub.3R),
trifluoromethyl (--CF.sub.3), ester (--COOR), amide (--CONHR or
--CONRR'), substituted or unsubstituted straight or branched chain
C.sub.1-C.sub.12 alkoxy, substituted or unsubstituted straight or
branched C.sub.1-C.sub.12 alkyl, substituted or unsubstituted
aromatic or non-aromatic heterocyclic rings, substituted or
unsubstituted aryl, substituted or unsubstituted mono- or
di-arylamine, and substituted or unsubstituted aralkylamine, and
each of R and R' are selected from a group consisting of
substituted or unsubstituted C.sub.1-C.sub.60 alkyl, substituted or
unsubstituted aryl, and substituted or unsubstituted 5-7 membered
heterocyclic rings.
[0055] Examples of the compound of Formula 1 may include compounds
represented by the following Formulae 1-1 to 1-6. ##STR2##
##STR3##
[0056] Other examples, synthesizing methods, and various features
of Formula 1 are disclosed in US Patent Application No.
2002-0158242 and U.S. Pat. Nos. 6,436,559 and 4,780,536, and the
contents of the above-mentioned documents are incoporated
herein.
[0057] Further, the n-type organic compound layer may contain at
least one compound selected from
2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ),
fluoro-substituted 3,4,9,10-perylenetetracarboxylic dianhydride
(PTCDA), cyano-substituted 3,4,9,10-perylenetetracarboxylic
dianhydride (PTCDA), naphthalene-tetracaboxylic-dianhydride
(NTCDA), fluoro-substituted naphthalene-tetracaboxylic-dianhydride
(NTCDA), or cyano-substituted
naphthalene-tetracaboxylic-dianhydride (NTCDA).
[0058] The electronic device according to the exemplary embodiment
of the invention includes the p-type organic compound layer being
in contact with the n-type organic compound layer of the first
electrode for hole injection or hole extraction. Therefore, the
n-type organic compound layer of the first electrode and the p-type
organic compound layer form the NP junction. FIG. 2 shows the NP
junction formed between the n-type organic compound layer of the
first electrode and the p-type organic compound layer.
[0059] When the NP junction is formed, the energy level difference
between the LUMO energy level of the n-type organic compound layer
of the first electrode and the HOMO energy level of the p-type
organic compound layer is reduced. Therefore, holes or electrons
are easily generated by an external voltage or a light source. The
NP junction causes holes and electrons to be easily generated in
the p-type organic compound layer and the n-type organic compound
layer of the first electrode, respectively. Since holes and
electrons are simultaneously generated in the NP junction, the
electrons are transported to the conductive layer of the first
electrode through the n-type organic compound layer of the first
electrode and holes are transported to the p-type organic compound
layer.
[0060] Examples of the electronic device according to the exemplary
embodiment of the invention include an organic light emitting
device, an organic solar cell, and an organic transistor, but are
not intended to limit the present invention.
[0061] Organic Light Emitting Device
[0062] An organic light emitting device includes an anode electrode
including a conductive layer and an n-type organic compound layer
positioned on the conductive layer; a cathode electrode; and a
p-type organic compound layer interposed between the n-type organic
compound layer and the cathode to form an NP-junction together with
the n-type organic compound layer. The organic light emitting
device may include at least one of a hole injection layer, a hole
transport layer, an emitting layer, an electron transport layer,
and an electron injection layer between the n-type organic compound
layer of the anode and the cathode.
[0063] FIGS. 3 to 5 illustrate organic light emitting devices
according to exemplary embodiments of the invention. Referring to
FIGS. 3 to 5, organic light emitting devices according to first to
third embodiments of the invention are formed as follows.
First Embodiment
[0064] substrate 31 [0065] anode 32: conductive layer 32a/n-type
organic compound layer 32b [0066] p-type hole injection layer 33
[0067] hole transport layer 34 [0068] emitting layer 35 [0069]
electron transport layer 36 [0070] cathode 37
Second Embodiment
[0070] [0071] substrate 31 [0072] anode 32: conductive layer
32a/n-type organic compound layer 32b [0073] p-type hole injection
layer 34 [0074] emitting layer 35 [0075] electron transport layer
36 [0076] cathode 37
Third Embodiment
[0076] [0077] substrate 31 [0078] anode 32 : conductive layer
32a/n-type organic compound layer 32b [0079] p-type emitting layer
35 [0080] electron transport layer 36 [0081] cathode 37
[0082] In the first to third embodiments, the hole transport layer
34 , the emitting layer 35, and the electron transport layer 36 may
be formed of the same organic compound or different organic
compounds. In the second embodiment, the n-type organic compound
layer 32b functions as a hole injection layer as well. In the third
embodiment, the n-type organic compound layer 32b functions as both
a hole injection layer and a hole transport layer.
[0083] In the first to third embodiments, an energy difference
between an LUMO energy level of the n-type organic compound layer
32b and the Fermi energy level of the conductive layer 32a is more
than 2 eV and equal to or less than 4 eV. In the first to third
embodiments, the p-type organic compound layer forming the NP
junction together with the n-type organic compound layer 32b is the
p-type hole injection layer 33, the p-type hole transport layer 34
, and the p-type emitting layer 35, respectively. As for the n-type
organic compound layer 32b and the p-type organic compound layer
forming the NP junction, the energy difference between an LUMO
energy level of the n-type organic compound layer 32b and an HOMO
energy level of the p-type organic compound layer is approximately
1 eV or less, and preferably, approximately 0.5 eV or less.
[0084] When the energy difference between the LUMO energy level of
the n-type organic compound layer 32b and the Fermi energy level of
the conductive layer 32a is lager than 4 eV, a surface dipole or
gap state effect on an energy barrier for injection of the holes
into the p-type hole injection layer is reduced. When the energy
difference between the LUMO energy level of the n-type organic
compound layer 32b and the HOMO energy level of the p-type hole
injection layer is lager than approximately 1 eV, holes or
electrons are not easily generated in the p-type organic compound
layer or the n-type organic compound layer 32b, respectively, and a
driving voltage for injection holes increases.
[0085] FIG. 6 illustrates an ideal energy level of an organic light
emitting device according to the related art. At this energy level,
a loss of energy for injecting holes and electrons from the anode
and the cathode, respectively, is minimized. FIG. 7 illustrates an
energy level of an organic light emitting device according to an
exemplary embodiment of the invention.
[0086] Referring to FIG. 7, an organic light emitting device
according to an exemplary embodiment of the invention includes an
anode including a conductive layer and an n-type organic compound
layer (see FIG. 3), a p-type hole injection layer HIL, a hole
transport layer HTL, an emitting layer EML, an electron transport
layer ETL, and a cathode. The energy difference between an LUMO
energy level of the n-type organic compound layer of the anode and
a Fermi energy level of the conductive layer of the anode is more
than 2 eV and equal to or less than 4 eV. Further, the energy
difference between the LUMO energy level of the n-type organic
compound layer of the anode and an HOMO energy level of the p-type
hole injection layer is approximately 1 eV or less. Since an energy
barrier for injecting or extracting holes/electrons is lowered by
the n-type organic compound layer of the anode, holes are easily
transported from the anode to the emitting layer using the LUMO
energy level of the n-type organic compound layer of the anode and
the HOMO energy level of the p-type hole injection layer.
[0087] Since the n-type organic compound layer of the anode lowers
the energy barrier for injecting holes from the anode to the p-type
hole injection layer, the p-type hole transport layer, or the
p-type emitting layer, the conductive layer of the anode may be
formed of various conductive materials. For example, the conductive
layer may be formed of a material having the same work function as
the cathode, such as Ca, Ca--Ag, Ca--IZO, or Mg--Ag. When the anode
is formed of the same material as the cathode, a stack-type organic
light emitting device in which a conductive material has a low work
function may be manufactured.
[0088] Since the cathode and the anode may be formed of the same
material, a stack-type organic light emitting device having a
structure, as shown in FIG. 10, in which at least two unit organic
light emitting devices each including an anode 71, a cathode 75,
and an organic compound layer 73 interposed therebetween are
connected in series, and a stack-type organic light emitting device
having a similar structure to the structure mentioned above, as
shown in FIG. 11, can be manufactured. In this case, the anode 71
includes a conductive layer and an n-type organic compound
layer.
[0089] Referring to FIG. 11, the stack-type organic light emitting
device according to the exemplary embodiment of the invention is
formed by stacking the cathode of a unit organic emitting device as
the anode of another adjacent unit organic light emitting device.
More specifically, the stack-type organic light emitting device has
a structure in which a plurality of repetition units, each of which
includes an organic compound layer 83 and a conductive interlayer
85 serving as the anode of a unit organic light emitting device and
the cathode of an adjacent unit organic light emitting device, are
stacked between an anode 81 and a cathode 87. In this stack-type
organic light emitting device, the conductive interlayer 85
comprises a conductive layer and an n-type organic compound layer.
The conductive layer is preferably formed of a transparent material
having a work function close to that of the material of the cathode
87 and visible light transmittance of 50% or more. When the
conductive layer is formed of a non-transparent metal, the
conductive layer should be made thin so as to transmit light.
Examples of the non-transparent metal include Al, Ag, Cu, Ca,
Ca--Ag, and the like. Ca having a low work function may be used to
form the conductive layer of the conductive interlayer 85. In
particular, when Ca--IZO is used to form the conductive interlayer
of the conductive interlayer 85, it is possible to improve visible
light transmittance. Since luminance of the stack-type organic
light emitting device increases in proportion to the number of
stacked unit organic light emitting devices at the same driving
voltage, when an organic light emitting device is formed in a stack
type, it is possible to obtain a high-luminance organic light
emitting device.
[0090] An organic light emitting device according to an exemplary
embodiment of the invention is manufactured by depositing a metal
or a conductive metal oxide or an alloy thereof on a substrate so
as to form an anode, forming thereon an organic compound layer
including a hole injection layer, a hole transport layer, an
emitting layer, and an electron transport layer, and depositing
thereon a material capable of being used as a cathode, using a PVD
(Physical Vapor Deposition) method, such as a sputtering method or
an e-beam evaporation method. Also, an organic light emitting
device according to an exemplary embodiment of the invention may be
manufactured by sequentially depositing a cathode material, an
organic compound layer, and an anode material on a substrate (see
International Patent Application No. 2003/012890).
[0091] The organic compound layer may have a multi-layer structure
including the hole injection layer, the hole transport layer, the
emitting layer, and the electron transport layer, but is not
intended to limit the present invention. The organic compound layer
may have a single-layer structure. Further, the organic compound
layer may be formed by a solvent process, using various
high-molecular-weight materials, such as spin coating, dip coating,
doctor blading, screen printing, inkjet printing, and thermal
transfer techniques, so as to have a smaller number of layers.
[0092] Hereinafter, individual layers constituting an organic light
emitting device according to an exemplary embodiment of the
invention will be described in detail. The material of each of the
layers that will be described below may be a single material or a
compound of at least two materials.
[0093] Anode
[0094] An anode injects holes into a p-type organic compound layer,
such as a hole injection layer, a hole transport layer, or an
emitting layer. The anode includes a conductive layer and an n-type
organic compound layer. The conductive layer contains a metal, a
metal oxide, or a conductive polymer. The conductive polymer may
include an electro-conductive polymer.
[0095] Since the n-type organic compound layer lowers the energy
barrier for injecting holes to a p-type organic compound layer, the
conductive layer may be formed of various conductive materials. For
example, the conductive layer has a Fermi energy level within a
range of approximately 2.5 eV to 5.5 eV. Examples of the conductive
material include carbon, aluminum, calcium, vanadium, chromium,
copper, zinc, silver, gold, other metals, and an alloy thereof;
zinc oxides, indium oxides, tin oxides, indium tin oxides (ITO),
indium zinc oxides (IZO), and metal oxides that are similar
thereto; and Ca--Ag or materials having a stacked structure of a
metal and a metal oxide such as Ca--IZO. When an organic light
emitting device of a normal structure including an anode as a lower
electrode is a top emission type, the conductive layer may be
formed of not only a transparent material but also a
non-transparent material having high reflectance. When an organic
light emitting device of the normal structure including the anode
as a lower electrode is a bottom emission type, the conductive
layer should be formed of a transparent material. If the conductive
layer is formed of a non-transparent material, the conductive layer
should be made thin so as to transmit light. This is conversely
applied to an organic light emitting device of an inverted
structure including an anode as an upper electrode.
[0096] The n-type organic compound layer is interposed between the
conductive layer and the p-type organic compound layer and injects
holes into the p-type organic compound layer at a low electric
field. The n-type organic compound layer is selected such that the
energy difference between an LUMO energy level of the n-type
organic compound layer of the anode and a Fermi energy level of the
conductive layer of the anode is more than 2 eV and equal to or
less than 4 eV and the energy difference between the LUMO energy
level of the n-type organic compound layer and an HOMO energy level
of the p-type organic compound layer is approximately 1 eV or less.
For example, the n-type organic compound layer has an LUMO energy
level in a range of approximately 4 eV to 7 eV and electron
mobility in a range of approximately 10.sup.-8 cm.sup.2/Vs to 1
cm.sup.2/Vs, preferably, approximately 10.sup.-6 cm.sup.2/Vs to
10.sup.-2 cm.sup.2/Vs. When the electron mobility is less than
approximately 10.sup.-8 cm.sup.2/Vs, it is not easy for the n-type
organic compound layer to inject holes into the p-type organic
compound layer.
[0097] The n-type organic compound layer may be formed of a
material capable of being vacuum-deposited or a material capable of
being formed into a thin film by a solution process. Examples of
the material of the n-type organic compound layer are not limited
thereto and include the above-mentioned materials.
[0098] Hole Injection Layer (HLT) or Hole Transport Layer (HTL)
[0099] The hole injection layer or the hole transport layer is a
p-type organic compound layer interposed between the anode and the
cathode and forms an NP junction together with the n-type organic
compound layer formed on the conductive layer of the anode. Holes
generated in the NP junction are transported to the emitting layer
through the p-type hole injection layer or the p-type hole
transport layer.
[0100] The energy difference between an HOMO energy level of the
p-type hole injection layer or the p-type hole transport layer
forming the NP junction and an LUMO energy level of the n-type
organic compound layer is approximately 1 eV or less, and
preferably, approximately 0.5 eV or less. Examples of the material
of the p-type hole injection layer or the p-type hole transport
layer include arylamine-based compounds, conductive polymers, or
block copolymers having both a conjugated portion and an
unconjugated portion, but are not intended to limit the present
invention.
[0101] Emitting Layer (EML)
[0102] In the emitting layer, hole transport and electron transport
occur at the same time. Therefore, the emitting layer may have both
of n-type characteristics and p-type characteristics. For
convenience, the emitting layer may be defined as the n-type
emitting layer when the electron transport is rapider than the hole
transport, and also defined as the p-type emitting layer when the
hole transport is rapider than the electron transport.
[0103] In the n-type emitting layer, since the electron transport
is rapider than the hole transport, light emission occurs in the
vicinity of the interface between the hole transport layer and the
emitting layer. Therefore, when an LUMO energy level of the hole
transport layer is higher than an LUMO energy level of the emitting
layer, higher light emission efficiency can exhibit. Examples of
the material of the n-type emitting layer include aluminum
tris(8-hydroxyquinoline) (Alq3); 8-hydroxyquinoline beryllium
(BAlq); a benzoxazole-based compound, a benzthiazol-based compound
or a benzimidazole-based compound; a polyfluorene-based compound;
and a silacyclopentadiene (silole)-based compound, but are not
intended to limit the present invention.
[0104] In the p-type emitting layer, since the hole transport is
rapider than the electron transport, light emission occurs in the
vicinity of the interface between the electron transport layer and
the emitting layer. Therefore, when an HOMO energy level of the
electron transport layer is lower than an HOMO energy level of the
emitting layer, higher light emission efficiency can exhibit. In a
case of using the p-type emitting layer, an increase effect
depending on a variation in the LUMO energy level of the hole
transport layer on the light emission efficiency is smaller
compared with a case of using the n-type emitting layer. Therefore,
in a case of using the p-type emitting layer, an organic light
emitting device having an NP junction of an n-type organic compound
layer and a p-type organic compound layer can be manufactured
without using the hole injection layer and the hole transport
layer. Examples of the material of the p-type emitting layer
include carbazole-based compounds, anthracene-based compounds,
polyphenylenevinylene (PPV)-based polymers, or spiro compounds, but
are not intended to limit the present invention.
[0105] Electron Transport Layer (ETL)
[0106] The material of the electron transport layer is preferably a
material having high electron mobility to effectively receive
electrons from the cathode and transport the electrons to the
emitting layer. Examples of the material of the electron transport
layer include aluminum tris(8-hydroxyquinoline) (Alq3), an organic
compound containing an Alq3 structure, or a hydroxy flavone-metal
complex compound or a silacyclopentadiene (silole)-based compound,
but are not intended to limit the present invention.
[0107] Cathode
[0108] The material of the cathode is preferably a material having
a low work function to easily inject electrons to the LUMO energy
level of the n-type organic compound layer such as the electron
transport layer. Examples of the material of the cathode include a
metal, such as magnesium, calcium, sodium, potassium, titanium,
indium, yttrium, lithium, gadolinium, aluminum, silver, tin, and
lead, or an alloy thereof; and materials having a multi-layer
structure, such as LiF/Al or LiO.sub.2/Al. Alternatively, the
cathode may be formed of the same material as the conductive layer
of the anode. The cathode or the conductive layer of the anode may
contain a transparent material.
[0109] Organic Solar Cell
[0110] An organic solar cell includes an anode, a cathode, and a
thin organic compound layer interposed between the anode and the
cathode. The thin organic compound layer includes a plurality of
layers to improve the efficiency and stability of the organic solar
cell. Referring to FIG. 8 , an organic solar cell according to an
exemplary embodiment of the invention may be formed as follows.
[0111] substrate 41 [0112] anode 42: conductive layer 42a/n-type
organic compound layer 42b [0113] electron donor layer 43 [0114]
electron acceptor layer 44 [0115] cathode 45
[0116] When the organic solar cell receives photons from an
external light source, electrons and holes are generated between
the electron donor layer 43 and the electron acceptor 44 and the
generated holes are transported to the anode 42 through the
electron donor layer 43. The electron donor layer 43 is formed of a
p-type organic compound layer so as to form an NP junction together
with the n-type organic compound layer of the anode. The p-type
organic compound layer may be formed of a compound of at least two
materials. An organic solar cell according to another exemplary
embodiment of the invention may further include an additional thin
organic compound layer or exclude a specific organic compound layer
to simplify the manufacturing process. When an organic compound
having various functions is used, it is possible to reduce the
number of organic compound layers of the organic solar cell.
[0117] A conventional organic solar cell according transports holes
to an anode along an HOMO energy level of an thin organic compound
layer, such as an electron donor layer. Therefore, as the energy
level difference between a Fermi energy level of the anode and an
HOMO energy level of an electron donor layer decreases, more holes
are extracted. However, in the organic solar cell according to the
exemplary embodiment of the invention, since an NP junction is
formed by the n-type organic compound layer 42b of the anode and
the electron donor layer 43, holes are extracted efficiently and
extracted holes are injected to the conductive layer 42a through an
LUMO energy level of the n-type organic compound layer 42b.
[0118] The energy difference between an LUMO energy level of the
n-type organic compound layer 42b of the anode and a Fermi energy
level of the conductive layer 42a of the anode is more than 2 eV
and equal to or less than 4 eV, and the energy difference between
the LUMO energy level of the n-type organic compound layer 42b and
an HOMO energy level of a p-type organic compound layer, such as
the electron donor layer 43, is approximately 1 eV or less.
Examples of the material of the conductive layer 42a may include
various materials each having different Fermi energy level. The
cathode 45 and the anode 42 may be formed of the same material.
[0119] In the organic solar cell, the conductive layer 42a of the
anode and the cathode 45 may be formed using the materials
exemplified as the materials of the conductive layer of the anode
and the cathode of the organic light emitting device. Further, the
n-type organic compound layer of the organic solar cell nay be
formed using the materials exemplified as the material of the
n-type organic compound layer of the organic light emitting device.
In the organic solar cell, the electron acceptor 44 may be formed
of the materials exemplified as the material of the electron
transport layer or the n-type emitting layer of the organic light
emitting device or materials known as fullerene-based compounds.
The electron donor layer 43 of the organic solar cell may be formed
of the materials exemplified as the material of the p-type hole
transport layer or the p-type emitting layer of the organic light
emitting device or thiophene-based polymers.
[0120] Organic Transistor
[0121] FIG. 9 illustrates an organic transistor according to an
exemplary embodiment of the invention.
[0122] Referring to FIG. 9, an organic transistor includes a
substrate 61, a source electrode 65, a drain electrode 66, a gate
electrode 62, an insulating layer 63 disposed on the substrate 61
and the gate electrode 62, and a p-type organic compound layer 64
that is disposed on the insulating layer 63 and generates holes. At
least one of the source electrode 65 and the drain electrode 66
includes a conductive layer 65a , 66a and an n-type organic
compound layer 67 forming an NP junction together with the p-type
organic compound layer 64. The energy difference between an LUMO
energy level of the n-type organic compound layer 67 of the source
electrode 65 or the drain electrode 66 and a Fermi energy level of
the conductive layer 65a , 66a is more than 2 eV and equal to or
less than 4 eV. The energy difference between the LUMO energy level
of the n-type organic compound layer 67 of the source electrode 65
or the drain electrode 66 and an HOMO energy level of the p-type
organic compound layer 64 is approximately 1 eV or less.
[0123] The n-type organic compound layer 67 of the source electrode
65 or the drain electrode 66 may extract holes from the conductive
layer 65a , 66a of the source electrode 65 and inject the holes to
the drain electrode 66 through the LUMO energy level. Since the NP
junction is formed between the p-type organic compound layer 64 and
the n-type organic compound layer 67 of the source electrode 65 or
the drain electrode 66 , the holes can be smoothly transported
between the source electrode 65 and the drain electrode 66 . In the
invention, since the n-type organic compound layer 67 forms a
portion of the source electrode 65 or the drain electrode 66 , the
conductive layers 65a, 66a of the source electrode 65 or the drain
electrode 66 may be formed using various material having different
Fermi energy levels.
[0124] In the organic transistor according to the exemplary
embodiment of the invention, the n-type organic compound layer 67
of the source electrode 65 or the drain electrode 66 may be formed
using the materials exemplified as the material of the n-type
organic compound layer of the organic light emitting device. The
gate electrode 62 may be formed using the materials exemplified as
the material of the anode or the cathode of the organic light
emitting device.
[0125] The conductive layer 65a , 66a of the source electrode 65 or
the drain electrode 66 may be formed using the materials
exemplified as the material of the anode of the organic light
emitting device. The p-type organic compound layer 64 may be formed
using pentacene-based compounds, antradithiophene-based compounds,
benzodithiophene-based compounds, thiophene-based oligomers,
polythiophenes, mixed-subunitthiophene oligomers, oxy-funcionalized
thiophene oligomers, or the like. The insulating layer 63 may be
formed of silicon oxide, silicon nitride; or a polymer such as
polyimide, poly(2-vinylpyridine), poly(4-vinylphenol) or
poly(methylmethacrylate).
MODE FOR INVENTION
[0126] Hereinafter, various aspects and features of the invention
will be described in detail by way of examples. However, the
following examples are just illustrative examples for describing
various aspects and features of the invention and the scope of the
invention is not limited to the following examples.
EXAMPLES
[0127] HOMO and LUMO energy levels of hexanitrile
hexaazatriphenylene by UPS and UV-VIS absorption method (See
Formula 1-1, HAT, Korea Patent Publication No. 2003-67773) were
measured by a method disclosed in PCT/KR2005/001381. The HOMO
energy level of HAT is 9.78 eV and the LUMO energy level of HAT is
6.54 eV. These levels can be changed by exciton binding energy of
HAT. 6.54 eV is higher than the Fermi energy level of HAT, that is,
6.02 eV. In order to make the LUMO energy level lower than Fermi
energy level, the exciton binding energy should be equal to or more
than 0.52 eV. Since exciton binding energy of an organic compound
is generally in a range of 0.5 eV to 1 eV, the LUMO energy level of
HAT is estimated to 5.54 eV to 6.02 eV.
[0128] A glass substrate (Corning 7059 glass) was immersed in
distilled water containing a detergent (Product No. 15-335-55 made
by Fischer Co.) to wash the substrate with ultrasonic waves for 30
minutes. Next, washing with ultrasonic waves for 5 minutes was
repeated twice by using distilled water. After the completion of
washing with distilled water, washing with ultrasonic waves was
carried out by using isopropyl alcohol, acetone and methanol in
this order. The resultant product was dried to be used.
Example 1
[0129] Organic Light Emitting Device Including Anode Having IZO--Ca
Conductive Layer and HAT n-Type Organic Compound Layer
[0130] IZO was vacuum-deposited on a washed glass substrate to have
a thickness of 1000 .ANG. using a sputtering deposition apparatus
and Ca was thermally vacuum-deposited thereon to have a thickness
of 100 .ANG.. As a result, a transparent IZO--Ca conductive layer
having a work function of 2.6 eV was formed. Then, HAT was
thermally vacuum-deposited on the formed conductive layer to have a
thickness of approximately 500 .ANG.. As a result, a transparent
anode having the IZO--Ca conductive layer and the HAT n-type
organic compound layer was formed. Subsequently,
4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was
vacuum-deposited on the anode to have a thickness of approximately
400 .ANG. so as to form a p-type hole transport layer. Next, Alq3
having an HOMO energy level of approximately 5.7 eV was
vacuum-deposited on the p-type hole transport layer to have a
thickness of approximately 300 .ANG. so as to form an emitting
layer. Then, the following compound (the HOMO energy level is
approximately 5.7 eV) was vacuum-deposited on the emitting layer to
have a thickness of 200 .ANG. so as to form an electron transport
layer. ##STR4##
[0131] Finally, lithium fluoride (LiF) was vacuum-deposited on the
electron transport layer to have a thickness of 12 .ANG. and then
aluminum (Al) was vacuum-deposited thereon to have a thickness of
2500 .ANG. so as to form a cathode. In such a manner, an organic
light emitting device was completed. In the processes of
manufacturing the organic light emitting device, the organic
compound depositing speed was maintained at approximately 0.4 to
0.7 .ANG./sec, the LiF depositing speed was maintained at
approximately 0.3 .ANG./sec, and the Ca or Al depositing speed was
maintained at approximately 2 .ANG./sec. During deposition, the
degree of vacuum in a deposition chamber was maintained at
approximately 2.times.10.sup.-7 to 5.times.10.sup.-8 torr.
Example 2
[0132] Organic Light Emitting Device Including Anode Having Ag--Ca
Conductive Layer and HAT n-Type Organic Compound Layer
[0133] An organic light emitting device was manufactured by the
same method as Example 1, except that Ag was thermally
vacuum-deposited on a washed glass substrate to have a thickness of
200 .ANG. and Ca was thermally vacuum-deposited thereon to have a
thickness of 200 .ANG. so as to form a semitransparent Ag--Ca
conductive layer having a work function of 2.6 eV, instead of the
transparent IZO--Ca conductive layer. TABLE-US-00001 TABLE 1 Work
@50 mA/cm.sup.2 @100 mA/cm.sup.2 function Voltage Luminance Voltage
Luminance Anode of anode (V) (cd/sq) (V) (cd/sq) Example 1 IZO(1000
.ANG.) 2.6 eV 5.10 1300 6.30 2663 --Ca(100 .ANG.) Example 2 Ag(200
.ANG.) 2.6 eV 4.20 500 4.80 1000 --Ca(200 .ANG.)
[0134] From Table 1 representing the luminance of Examples 1 and 2
depending on a current density and a voltage, it can be seen that
holes are smoothly injected to the hole transport layer even though
the energy difference between the LUMO energy level (approximately
5.54 eV to 6.02 eV) of the n-type organic compound layer (HAT) and
the Fermi energy level (2.6 eV) of the conductive layer is 2.9 eV
to 3.4 eV. This means that, in a range in which the energy
difference between the LUMO energy level of the n-type organic
compound layer and the Fermi energy level of the conductive layer
is more than 2 eV and equal to or less than 4 eV, the
current-voltage characteristic of the organic light emitting device
is independent of the Fermi energy level of the conductive
layer.
[0135] The luminance of the organic light emitting device according
to Example 2 is lower than the luminance of the organic light
emitting device according to Example 1. This is because the visible
light transmittance of the Ag (200 .ANG.)-Ca (200 .ANG.) conductive
layer is lower than IZO (1000 .ANG.)-Ca (100 .ANG.). Considering
the visible light transmittance, it is determined that the
luminance of the organic light emitting device according to Example
2 is equivalent to the luminance of a device having the conductive
layer of Example 1.
[0136] The above-mentioned results of Table 1 represent that it is
possible to use, as an anode of an organic light emitting device,
an electrode that includes a conductive layer formed of a material
having a low Fermi energy level, such as Ca, to be used as a
cathode electrode; an n-type organic compound layer, in which a
difference between an LUMO energy level of the n-type organic
compound layer and a Fermi energy level of the conductive layer is
more than 2 eV and equal to or less than 4 eV; and a p-type organic
compound layer that forms an NP junction together with the n-type
organic compound layer, in which a difference between an HOMO
energy level of the p-type organic compound layer and the LUMO
energy level of the n-type organic compound layer is 1 eV or less.
This means that it is possible to form the conductive layer of the
anode and the cathode of the same material, and to realize a
stack-type organic light emitting device shown in FIG. 11 in which
a conductive layer of an anode and a cathode are formed of the same
material.
* * * * *