KR20160090780A - Organic Light Emitting Display Device - Google Patents

Abstract

The present invention provides an organic light emitting display device including a substrate, a first electrode, an organic light emitting layer, and a second electrode. The first electrode is located on the substrate. The organic light emitting layer is located on the first electrode. The second electrode is located on the organic light emitting layer. The organic light emitting layer includes a light emitting layer having at least one host and at least two dopants. Levels of a highest occupied molecular orbital (HOMO) and a lowest occupied molecular orbital (LUMO) of the at least two dopants are between levels of the HOMO and the LUMO of the at least one host. The at least two dopants include first and second dopants, and the first and second dopants are formed of materials to represent the same color. The first dopant satisfies the equation relationship: the HOMO level of the host - 0.1 eV < the HOMO level of the first dopant < the HOMO level of the host. The second dopant satisfies the equation relationship: the HOMO level of the host - 0.5 eV < the HOMO level of the second dopant < the HOMO level of the host - 0.1 eV. Accordingly, the energy transition between the host and the dopants can be easily achieved to improve a service life and efficiency thereof.

Description

[0001] The present invention relates to an organic light emitting display device,

The present invention relates to an organic light emitting display.

An organic electroluminescent device used in an organic electroluminescent display device is a self-luminous device in which a light emitting layer is formed between two electrodes. The organic electroluminescent device injects electrons and holes from the electron injecting electrode and the hole injecting electrode into the light emitting layer, and excites the excited electrons and holes, And emits light when it is dropped to the ground state.

The organic light emitting display device using the organic electroluminescent device has a top emission mode, a bottom emission mode and a dual emission mode depending on a direction in which light is emitted, Passive matrix type and active matrix type according to the following.

In the organic light emitting display, when a scan signal, a data signal, a power supply, and the like are supplied to a plurality of subpixels arranged in a matrix form, the selected subpixel emits light, thereby displaying an image.

Organic electroluminescent display devices use materials and structures capable of exhibiting the best characteristics for red, green and blue subpixels. The organic electroluminescent display device has a problem that the luminescent characteristics and lifespan of the device deteriorate over time. Thus, in recent years, structures for improving the light emission characteristics and lifetime of devices have been continuously proposed.

SUMMARY OF THE INVENTION [0008] The present invention for solving the above-mentioned problems of the related art is to provide an organic electroluminescent display device which facilitates energy transfer between a host and a dopant, thereby improving lifetime and efficiency.

In order to solve the above-mentioned problems, the present invention provides a semiconductor device comprising: a substrate; A first electrode located on the substrate; An organic light emitting layer disposed on the first electrode; And a second electrode located on the organic light emitting layer, wherein the organic light emitting layer comprises a light emitting layer comprising at least one host and at least two dopants, wherein the homo and ramo levels of the at least two dopants are at least Wherein the at least two dopants comprise a first dopant and a second dopant, wherein the first and second dopants comprise a material that emits the same color , The first dopant has a mathematical relationship such as a homo level of the host - 0.1 eV <a homo level of the first dopant <a homo level of the host, and a second dopant has a homo level of the host - 0.5 eV < And a homo level of the second dopant (a homo level of the host - 0.1 eV).

The first dopant may be adjacent to the electron transport layer included in the organic light emitting layer, and the second dopant may be adjacent to the hole transport layer included in the organic light emitting layer.

The at least two dopants may be selected as a material that facilitates energy transfer with the at least one host.

The first dopant may have a lower homo level than the second dopant so as to prevent the energy transfer trap charge phenomenon and to increase the hole transmission rate to the at least one host.

The homo level of the first dopant may be lower than the homo level of the second dopant and the ramos level of the first dopant may be higher than or equal to the ramos level of the second dopant.

Wherein the at least one host comprises carbazole biphenyl (CBP) or mCP (1,3-bis carbazol-9-yl), and the at least two dopants comprise PIQIr (acac) at least one selected from the group consisting of bis (1-phenylisoquinoline) acetylacetonate iridium, PQIr (acac) bis (1-phenylquinoline) acetylacetonate iridium, PQIr (1-phenylquinoline) iridium and PtOEP (octaethylporphyrin platinum) Or PBD: Eu (DBM) ₃ (Phen) or Perylene.

Wherein the at least one host comprises carbazole biphenyl (CBP) or mCP (1,3-bis (carbazol-9-yl)) and the at least two dopants comprise Ir (ppy) ₃ (fac-tris (2-phenylpyridine) iridium) or Alq ₃ (tris (8-hydroxyquinolino) aluminum).

Wherein the at least one dopant comprises carbazole biphenyl (CBP) or mCP (1,3-bis (carbazol-9-yl) F2ppy) ₂ Irpic or spiro-DPVBi, spiro-6P, distyrylbenzene (DSB), distyrylarylene (DSA), PFO-based polymer and PPV-based polymer.

The organic light emitting layer includes a hole transporting layer adjacent to the light emitting layer, and the homo and ramo levels of the hole transport layer may be lower than the homo and ramo levels of the at least one host.

The organic light emitting layer includes an electron transporting layer adjacent to the light emitting layer, and the homo and ramo levels of the electron transporting layer may be lower than the homo and ramo levels of the at least one host.

The present invention provides an organic electroluminescent display device which facilitates energy transfer between a host and a dopant to improve lifetime and efficiency.

1 is a plan view of an organic light emitting display according to an embodiment of the present invention;
2 is a sectional view of the region A1-A2 shown in Fig.
3 is a cross-sectional exemplary view of the subpixel shown in FIG.
4 is a hierarchical view of an organic light emitting layer.
5 is a view for explaining an organic light emitting layer according to an embodiment of the present invention.
6 is an enlarged view of the light emitting layer shown in Fig.
7 is a graph showing current and voltage characteristics for comparison between the comparative example and the embodiment;
8 is a lifetime graph for comparison between the comparative example and the example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a plan view of an organic light emitting display according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the region A1-A2 shown in FIG.

1 and 2, an organic light emitting display according to an exemplary embodiment of the present invention includes a substrate 110 having a display area AA defined by sub-pixels SP formed in a matrix, 110 for protecting the sub-pixels SP from moisture or oxygen. The subpixels SP are formed into a passive matrix or an active matrix. When the subpixels SP are formed in the active matrix type, they may be formed of a 2T (Capacitor) structure including a switching transistor, a driving transistor, a capacitor, and an organic light emitting diode, or a structure in which transistors and capacitors are further added .

The substrate 110 and the sealing substrate 140 are integrally sealed by an adhesive member 180 formed in a non-display area NA located outside the display area AA. However, the sealing substrate 140 may be sealed by a multi-protective film composed of an organic, inorganic, or organic composite material. The organic light emitting display includes a pad unit 170 provided on an outer periphery of a substrate 110 to receive various signals or power from the outside and a driving unit 160 composed of a single chip, ) Are driven. Although the driving device 160 includes the data driver and the scan driver, the driver 160 may be divided into the non-display area NA in the case of the scan driver.

Hereinafter, the structure of subpixels will be described in more detail.

FIG. 3 is a cross-sectional view of a subpixel shown in FIG. 1, and FIG. 4 is a hierarchical view of an organic emission layer.

As shown in FIG. 3, a buffer layer 111 is disposed on the substrate 110. The buffer layer 111 may be formed to protect a thin film transistor formed in a subsequent process from an impurity such as an alkali ion or the like flowing out from the substrate 110. The buffer layer 111 may be made of silicon oxide (SiOx), silicon nitride (SiNx), or the like.

On the buffer layer 111, a gate 112 is located. The gate 112 is formed of any one selected from the group consisting of molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper Or a single layer or multiple layers of one or more of these alloys.

A first insulating film 113 is located on the gate electrode 112. The first insulating layer 113 may be a silicon oxide layer (SiOx), a silicon nitride layer (SiNx), or a multilayer thereof, but is not limited thereto.

An active layer 114 is located on the first insulating film 113. The active layer 114 may comprise amorphous silicon or polycrystalline silicon crystallized therefrom. Although not shown here, the active layer 114 may include a channel region, a source region, and a drain region, and the source region and the drain region may be doped with P-type or N-type impurities. In addition, the active layer 114 may include an ohmic contact layer for lowering the contact resistance.

On the active layer 114, a source electrode 115a and a drain electrode 115b are located. The source electrode 115a and the drain electrode 115b may be formed of a single layer or multiple layers and may be formed of a single layer of molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu). Alternatively, when the source electrode 115a and the drain electrode 115b are multilayered, they may be formed of a triple layer of molybdenum / aluminum-neodymium, molybdenum / aluminum / molybdenum, or molybdenum / aluminum-neodymium / molybdenum.

A second insulating film 116 is disposed on the source electrode 115a and the drain electrode 115b. The second insulating film 116 may be a silicon oxide film (SiOx), a silicon nitride film (SiNx), or a multilayer thereof, but is not limited thereto. The second insulating film 116 may be a passivation film.

A third insulating film 117 is formed on the second insulating film 116. The third insulating film 117 may be a silicon oxide film (SiOx), a silicon nitride film (SiNx), or a multilayer thereof, but is not limited thereto. The third insulating film 117 may be a planarizing film.

The above is a description of a totem gate type driving transistor located on the substrate 110. Hereinafter, the organic light emitting diode positioned on the driving transistor will be described.

A first electrode 119 is located on the third insulating film 117. The first electrode 119 may be selected as an anode or a cathode. The first electrode 119 selected as the anode may be a transparent material such as indium tin oxide (ITO) or indium zinc oxide (IZO), but is not limited thereto.

On the first electrode 119, a bank layer 120 having an opening exposing a part of the first electrode 119 is positioned. The bank layer 120 may include organic materials such as benzocyclobutene (BCB) resin, acrylic resin or polyimide resin, but is not limited thereto.

The organic light emitting layer 121 is located in the opening of the bank layer 120. The organic light emitting layer 121 includes a hole injection layer 121a, a hole transport layer 121b, a light emitting layer 121c, an electron transport layer 121d and an electron injection layer 121e as shown in FIG.

The hole injection layer 121a may serve to smooth the injection of holes and may be formed of a material such as cupper phthalocyanine, PEDOT (poly (3,4) -ethylenedioxythiophene), PANI (polyaniline) and NPD (N, -N, N'-diphenyl benzidine), but the present invention is not limited thereto.

The hole transport layer 121b plays a role of facilitating the transport of holes and includes a hole transporting material such as NPD (N, N-dinaphthyl-N, N'-diphenyl benzidine), TPD (N, N'- , N'-bis- (phenyl) -benzidine), s-TAD and MTDATA (4,4 ', 4 "-tris (N-3-methylphenyl-N-phenylamino) But is not limited thereto.

The light emitting layer 121c may include materials emitting red, green, blue, and white light, and includes at least one host and at least two dopants. When the light emitting layer 121c emits red light, it includes a host material containing CBP (carbazole biphenyl) or mCP (1,3-bis (carbazol-9-yl), and PIQIr (acac) (bis (1-phenylisoquinoline ) acetylacetonate iridium, PQIr (acac) bis (1-phenylquinoline) acetylacetonate iridium, PQIr (tris (1-phenylquinoline) iridium) and PtOEP (octaethylporphyrin platinum) (DBM) ₃ (Phen) or perylene. Alternatively, when the light emitting layer 121c emits green light, the light emitting layer 121c may be formed of CBP or It includes a host material including mCP, and be formed of a phosphorescence material including a dopant material including _{Ir (ppy) 3 (fac-} tris (2-phenylpyridine) iridium), Alternatively, Alq ₃ (tris ( 8-hydroxyquinolino) aluminum). Although it not limited to this. Emitting layer phosphor (121c) for emitting blue light in this case, includes a host material including CBP, or mCP, including a dopant material including (4,6-F2ppy) ₂ Irpic Alternatively, a fluorescent material containing any one selected from the group consisting of spiro-DPVBi, spiro-6P, distyrylbenzene (DSB), distyrylarylene (DSA), PFO- But the present invention is not limited thereto. Hosts and dopants constituting the light emitting layer 121c will be described in more detail below.

The electron transport layer 121d plays a role of facilitating transport of electrons and is made of at least one selected from the group consisting of Alq ₃ (tris (8-hydroxyquinolino) aluminum), PBD, TAZ, spiro-PBD, BAlq and SAlq But is not limited thereto.

The electron injection layer 121 e may be used to facilitate the injection of electrons and may include Alq ₃ (tris (8-hydroxyquinolino) aluminum), PBD, TAZ, LiF, spiro-PBD, BAlq or SAlq. Do not. The embodiment of the present invention is not limited to FIG. 4, and at least one of the hole injection layer 121a, the hole transport layer 121b, the electron transport layer 121d, and the electron injection layer 121e may be omitted.

A second electrode 122 is located on the organic light emitting layer 121. The second electrode 122 may be selected as a cathode or an anode. The second electrode 122 selected as the cathode may be aluminum (Al) or the like, but is not limited thereto.

Hereinafter, the organic light emitting layer 121 according to one embodiment of the present invention will be described in more detail.

FIG. 5 is a view for explaining an organic light emitting layer according to an embodiment of the present invention, and FIG. 6 is an enlarged view of the light emitting layer shown in FIG.

As shown in FIGS. 5 and 6, an organic light emitting layer 121 according to an embodiment of the present invention is formed between the first electrode 119 and the second electrode 122. The organic light emitting layer 121 includes a common layer including a light emitting layer 121c and a hole injecting layer 121a, a hole transporting layer 121b, an electron transporting layer 121d and an electron injecting layer 121e.

The light emitting layer 121c includes at least one host and two dopants Dopant 1 and Dopant 2. At least one host may be divided into layers according to the configuration of two dopants (Dopant 1, Dopant 2) or the deposition method. The first dopant 1 of the two dopants Dopant 1 and Dopant 2 is adjacent to the electron transport layer 121d included in the organic light emitting layer 121 and the second dopant 2 is doped into the organic light emitting layer 121 And the hole transport layer 121b included in the hole transport layer 121b. Here, the homo and ramo levels of the hole transport layer 121b may be lower than the homo and ramo levels of at least one host. The homo and ramo levels of the electron transport layer 121d may be lower than the homo and romo levels of at least one host.

The Highest Occupied Molecular Orbital (HOMO) and Lowest Occupied Molecular Orbital (LUMO) levels of the two dopants Dopant 1 and Dopant 2 are located between the homo and romo levels of the host. However, at least one of the homo and romo levels of the two dopants (Dopant 1, Dopant 2) is different. Therefore, the ramos level of the first dopant (Dopant 1) of the two dopants (Dopant 1, Dopant 2) is higher than that of the second dopant (Dopant 2) of the two dopants It can be higher or equal. In other words, the ramo level of the second dopant 2 may be less than or equal to the ramos level of the first dopant 1. On the other hand, the two dopants (Dopant 1, Dopant 2) have different levels of homo and romo levels, and the level difference between them is small. To this end, the two dopants (Dopant 1, Dopant 2) can be made of the same or different materials.

The first dopant 1 has the same mathematical relationship as the homo level of the host (Host) - 0.1 eV <the homo level of the first dopant 1 <the homo level of the host. And the second dopant 2 has a mathematical relationship such as the homo level of the host (Host) - 0.5 eV <the homopole level of the second dopant 2 <the homo level of the host - 0.1 eV. If the first dopant 1 and the second dopant 2 have the above-described formula relation with respect to the host, energy transfer trap charge caused by the dopant does not occur and the hole transfer rate to the host is increased . Further, it becomes possible to induce light emission over a wide area of the light emitting layer 121c. For example, if the homo and ramo levels of the host are 5.98 eV and 2.95 eV, the homo and ramo levels of the first dopant (Dopnat 1) may be 5.95 eV and 3.15 eV, respectively, and the second dopant The homo and ramo levels of Dopant 2) may consist of, but are not limited to, 5.83 eV and 3.03 eV.

Hereinafter, examples for comparison will be described in more detail to facilitate understanding of the present invention.

FIG. 7 is a graph showing current and voltage characteristics for comparison between the comparative example and the embodiment, and FIG. 8 is a graph showing the lifetime graph for comparison between the comparative example and the embodiment.

Table 1 below shows the voltage (V), luminous intensity (cd / A), current (Im / W) and color coordinates (CIEx, CIEy) measured in the structures of the comparative example and the example.

In the examples 1 to 7 and 8, the embodiment (Emb) and the comparative example (Ref) are the same as those in the embodiment 1 except that the hole injection layer 121a, the hole transport layer 121b, the electron transport layer 121d and the electron injection layer 121e ) Are formed in the same structure. However, the emissive layer 121c of the embodiment (Emb) is composed of at least one host and two dopants (Dopant 1 and Dopant 2) as shown in the structures of FIGS. 5 and 6, And the light emitting layer 121c of the light emitting layer Ref is made up of a host (host) and a second dopant (Dopant 2) shown in FIG. The hole injection layer 121a, the hole transport layer 121b, the electron transport layer 121d and the electron injection layer 121e were formed to a thickness of 700 Å, 200 Å and 10 Å, respectively. The host is made of a material composed of 5.98 eV and 2.95 eV at the homo and ramo levels, a material composed of 5.95 eV and 3.15 eV at the first dopant (Dopnat 1), and a material composed of the second dopant (Dopant 2 ) Was selected as a material composed of homo and ramo levels of 5.83 eV and 3.03 eV.

Referring to Table 1, FIG. 7 and FIG. 8, it can be seen that the structure of the comparative example (Ref) exhibits excellent characteristics in terms of the driving voltage and the lifetime. On the other hand, the structure of the embodiment (Emb) can exhibit chromaticity coordinates (CIEx, CIEy) characteristics similar to those of the comparative example (Ref), and shows excellent driving current and lifetime characteristics.

As can be seen from the comparison result between the embodiment (Emb) and the comparative example (Ref), even if the structure of the common layer except for the light emitting layer 121c has the same condition, one dopant (Dopnat 1, Dopant 2), which have similar energy levels, to at least one host (host). Further, according to the embodiment (Emb), it was found that the life time was improved as the difference between the two ramp and homo levels between the two dopants (Dopnat 1 and Dopant 2) was smaller. In addition, according to the embodiment (Emb), it is found that the effect of improving the lifetime is greater as the difference in energy level between the hole transport layer 121b and the light emitting layer 121c is larger.

The reason why the lifetime is increased as in the embodiment (Emb) is that the first dopant (Dopant 1) has a lower homo level than the second dopant (Dopant 2), which causes energy transfer trap charge phenomenon by the dopant And the holes have increased the transmission rate to the host. Therefore, although the embodiment (Emb) tends to decrease somewhat in terms of the efficiency of the device, it is possible to induce light emission over a wide area of the light emitting layer 121c in terms of the lifetime of the device, The effect of improving the service life was significant.

As described above, the present invention provides an organic electroluminescent display device that facilitates energy transfer between a host and a dopant, thereby improving lifetime and efficiency.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that the invention may be practiced. It is therefore to be understood that the embodiments described above are to be considered in all respects only as illustrative and not restrictive. In addition, the scope of the present invention is indicated by the following claims rather than the detailed description. Also, all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

110: substrate 140: sealing substrate
119: first electrode 121: organic light emitting layer
122: second electrode 121c: light emitting layer
Host: Host Dopant 1: First Dopant
Dopant 2: second dopant

Claims (10)

Board;
A first electrode located on the substrate;
An organic light emitting layer disposed on the first electrode; And
And a second electrode located on the organic light emitting layer,
The organic light-
A luminous layer of at least one host and at least two dopants, wherein the homo and romo levels of the at least two dopants are located between the homo and romo levels of the at least one host,
Wherein the at least two dopants comprise a first dopant and a second dopant, the first and second dopants being made of a material emitting the same color,
The first dopant has a mathematical relationship such as homo level of the host - 0.1 eV <homo level of the first dopant <homo level of the host,
The second dopant has a mathematical relationship such as a homo level of the host - 0.5 eV, a homo level of the second dopant, and a homo level of the host - 0.1 eV. The method according to claim 1,
The first dopant is adjacent to the electron transport layer included in the organic light emitting layer,
And the second dopant is adjacent to the hole transport layer included in the organic light emitting layer. The method according to claim 1,
The at least two dopants
Wherein the organic electroluminescent display device is selected from a material that facilitates energy transfer with the at least one host. The method according to claim 1,
Wherein the first dopant has a lower homo level than the second dopant so as to prevent the energy transfer trap charge phenomenon and to increase the hole transmission rate to the at least one host. The method according to claim 1,
The homo level of the first dopant is lower than the homo level of the second dopant,
Wherein the ramp level of the first dopant is higher than or equal to the ramp level of the second dopant. The method according to claim 1,
When the light emitting layer emits red light,
Wherein the at least one host comprises carbazole biphenyl (CBP) or mCP (1,3-bis (carbazol-9-yl)
The at least two dopants are selected from the group consisting of PIQIr (acac) bis (1-phenylisoquinoline) acetylacetonate iridium, PQIr (acac) bis (1-phenylquinoline) acetylacetonate iridium, PQIr platinum) or PBD: Eu (DBM) ₃ (Phen) or Perylene. The method according to claim 1,
When the light emitting layer emits green light,
Wherein the at least one host comprises carbazole biphenyl (CBP) or mCP (1,3-bis (carbazol-9-yl)
Wherein the at least two dopants comprise Ir (ppy) ₃ (fac-tris (2-phenylpyridine) iridium) or Alq ₃ (tris (8-hydroxyquinolino) aluminum). The method according to claim 1,
When the light emitting layer emits blue light,
Wherein the at least one host comprises carbazole biphenyl (CBP) or mCP (1,3-bis (carbazol-9-yl)
Wherein the at least two dopants are selected from the group consisting of (4,6-F2ppy) ₂ Irpic or spiro-DPVBi, spiro-6P, distyrylbenzene (DSB), distyrylarylene (DSA), PFO- The organic electroluminescent display device comprising: The method according to claim 1,
The organic light-
And a hole transporting layer adjacent to the light emitting layer,
Wherein the homo and ramo levels of the hole transport layer are lower than the homo and ramo levels of the at least one host. The method according to claim 1,
The organic light-
An electron transport layer adjacent to the light emitting layer,
Wherein the homo and romo levels of the electron transport layer are lower than the homo and ramo levels of the at least one host.

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