WO2015065074A1 - Organic light emitting diode, and display device and illumination including same - Google Patents

Abstract

The present invention relates to an organic light emitting diode, and a display device and an illumination including the same, the organic light emitting diode comprising: a substrate; a lower electrode formed on the substrate; an n-doping layer formed on the lower electrode; an organic light emitting layer formed on the n-doping layer; an organic layer including a hole transport layer formed on the organic light emitting layer and a hole injection layer formed on the hole transport layer and having a crystalline organic compound; a transparent upper electrode formed on the organic layer; and a capping layer formed on the transparent upper electrode, wherein the capping layer has a refractive index of 1.0 inclusive to 2.0 exclusive.

Description

Organic light emitting device, and display device and lighting including same

The present invention relates to an organic light emitting device and a display device and lighting including the same. Specifically, the present invention relates to an organic light emitting device that solves the color deviation problem according to the viewing angle, and a display device and lighting including the same.

When an organic light emitting diode applies a voltage between an anode and a cathode of an organic light emitting diode, holes injected from the anode move to the light emitting layer via the hole transport layer, and electrons injected from the cathode pass through the electron transport layer. And the holes and electrons (carriers) are self-luminous devices driven by the principle of recombination in the light emitting layer to generate excitons, which emit light as the excitons change from the excited state to the ground state.

Compared with conventional light sources such as CCFLs (cold cathode tubes), the organic light emitting device has a wide viewing angle, excellent contrast, fast response time, excellent luminance, driving voltage and response speed, and multi-coloring. Has

However, such organic light emitting devices still have color deviations depending on the viewing angle, and therefore, measures for securing a wider viewing angle are necessary.

Accordingly, an object of the present invention is to provide an organic light emitting device that does not generate color deviation according to the viewing angle, and a display device and lighting including the same.

One aspect of the present invention to achieve the above object of the present invention; A lower electrode formed on the substrate; An n-doped layer formed on the lower electrode, an organic light emitting layer formed on the n-doped layer, a hole transport layer formed on the organic light emitting layer, and a hole injection layer formed on the hole transport layer and including a crystalline organic compound An organic layer comprising a layer; A transparent upper electrode formed on the organic layer; And a capping layer formed on the transparent upper electrode, wherein the capping layer provides an organic light emitting device having a refractive index of 1.0 to less than 2.0.

In one embodiment of the present invention, the refractive index of the capping layer may be 1.2 to 1.5.

In a further embodiment of the invention, the capping layer may comprise a fluoride compound.

In a further embodiment of the present invention, the fluoride compound may be at least one selected from the group consisting of LiF, MgF ₂ , CaF ₂ and ScF ₃ .

In a further embodiment of the invention, the capping layer may comprise particles of a size smaller than the wavelength of light emitted from the organic layer.

In a further embodiment of the present invention, the capping layer may comprise two or more layers having different refractive indices.

In a further embodiment of the invention, the capping layer may have a thickness of 20 to 120 nm.

In a further embodiment of the invention, the n-doped layer comprises an n-dopant, wherein the n-dopant is Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , Cs ₂ CO ₃ , Rb ₂ CO ₃ , Ba ₂ CO ₃ , pyronin B, DMC (decamethylcobaltocene), BEDTTTF (bis (ethylenedithio) -tetrathiafulvalene), rhodamine B (rhodamin B), TMBI (1 , 2,3-trimethyl-2-phenyl-2,3-dihydro-1H-benzoimidazole), DMBI (1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzoimidazole) , Cl-DMBI (dichlorophenyl-1,3-dimethyl-2,3-dihydro-1H-benzoimidazole), N-DMBI (4- (1,3-dimethyl-2,3-dihydro-1H- Benzoimidazol-2-yl) -phenyl) -dimethyl-amine), OH-DMBI (2- (1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl) -phenol) , PTCDI-C13 (N, N'-ditridecylperylene-3,4: 9,10-tetracarboxylic acid diimide) and F-PTCDI-C4 (N, N'-dibutyl-1,7- Difluoroperylene-3,4: 9,10-tetracarboxylic acid diimide) may be one or more selected from the group consisting of .

In a further embodiment of the present invention, the n-doped layer may include an impurity layer including an n-dopant and a first electron transport layer including a first electron transport material formed on the impurity layer.

In a further embodiment of the present invention, the crystalline organic compound may be represented by the following formula (1).

[Formula 1]

In Formula 1, R is cyano (-CN), nitro (-NO ₂ ), phenylsulfonyl (-SO ₂ (C ₆ H ₅ )), cyano or nitro substituted C ₂ to C ₅ alkenyl, and It is selected from the group consisting of phenyl substituted with cyano or nitro.

In a further embodiment of the invention, the crystalline organic compound may be HAT-CN (hexaazatriphenylene hexacarbonitrile).

In a further embodiment of the invention, the upper electrode may comprise ITO (indium tin oxide), IZO (indium zinc oxide), ZnO (zinc oxide) or SnO ₂ (tin oxide).

In order to achieve the above object of the present invention, another aspect of the present invention provides a display device including the organic light emitting device as described above.

In order to achieve the above object of the present invention, another aspect of the present invention provides an illumination including the organic light emitting device as described above.

The organic light emitting device of the present invention can secure a wide viewing angle by reducing the color variation according to the viewing angle, that is, the phenomenon of changing the spectrum of light emitted according to the viewing angle. In addition, the organic light emitting device of the present invention has excellent light efficiency even when the capping layer is used, and the red light emitting device, the green light emitting device, and the blue light emitting device do not need to change the thickness of the capping layer according to the light emission color of the organic light emitting device. The process is simple as it can be applied in about the same to similar thicknesses.

1 is a schematic cross-sectional view of a structure of an organic light emitting diode according to an embodiment.

FIG. 2A illustrates emission spectra according to viewing angles of 0 ° to 60 ° in a blue organic light emitting device without a capping layer of Comparative Example 1. FIG.

FIG. 2B illustrates the emission spectrum according to the viewing angle change of 0 ° to 60 ° in the blue organic light emitting device having the capping layer of Example 1. FIG.

3 shows color coordinate values calculated from the emission spectra of FIGS. 2A and 2B.

FIG. 4A illustrates an emission spectrum according to a change in viewing angle of 0 ° to 60 ° in the green organic light emitting device without the capping layer of Comparative Example 2.

4B illustrates emission spectra according to viewing angles of 0 ° to 60 ° in the green organic light emitting device having the capping layer of Example 2. FIG.

FIG. 5 shows color coordinate values calculated from the emission spectra of FIGS. 4A and 4B.

FIG. 6A illustrates an emission spectrum according to a change in viewing angle of 0 ° to 60 ° in a red organic light emitting device without a capping layer of Comparative Example 3.

FIG. 6B illustrates emission spectra according to viewing angles of 0 ° to 60 ° in the red organic light emitting diode having the capping layer of Example 3. FIG.

FIG. 7 shows color coordinate values calculated from the emission spectra of FIGS. 6A and 6B.

8 illustrates a change in light efficiency (quantum yield) of the organic light emitting device according to the refractive index and the thickness of the capping layer.

9A, 9B, 9C, and 9D illustrate the change in viewing angle of 0 ° to 60 ° of a green organic light emitting diode using a high refractive index material having a refractive index of 2.4 in a capping layer having a thickness of 5 nm, 10 nm, 15 nm, and 20 nm, respectively. The emission spectrum is shown.

10 shows color coordinate values calculated from the emission spectra of FIGS. 9A to 9D and the emission spectrum of FIG. 4B.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiments introduced herein are provided only to ensure that the contents disclosed herein can be sufficiently delivered to those skilled in the art, and the present invention is not limited to the embodiments, and may be embodied in other forms. Like reference numerals in the drawings refer to like elements.

1 is a cross-sectional view schematically showing the structure of an organic light emitting device 100 according to an embodiment.

Referring to FIG. 1, the organic light emitting diode 100 may include a substrate 101, a lower electrode 110 formed on the substrate 101, an organic layer 120 formed on the lower electrode 110, and the lower electrode ( The transparent upper electrode 130 formed on the organic layer 120 and facing the 110 may include a capping layer 141 formed on the upper electrode 130.

The organic layer 120 includes an n-doped layer 123, an organic light emitting layer 125 formed on the n-doped layer 123, a hole transport layer 126 formed on the organic light emitting layer 125, and the hole transport layer ( 126 and a hole injection layer 127 formed on the crystalline organic compound. Optionally, an electron injection layer (not shown) may be further formed between the lower electrode 110 and the n-doped 123.

As the substrate 101, a glass substrate or a plastic substrate having excellent mechanical strength, thermal stability, transparency, surface smoothness, ease of handling, and waterproofness may be used. For example, the substrate 101 may include SiO ₂ as a main component. Transparent glass substrates can be used.

The lower electrode 110 formed on the substrate 101 may be electrically connected to the driving transistor to receive a driving current from the driving transistor. The lower electrode 110 may be formed of a metal having high reflectance, and it is preferable to use a material having a work function smaller than 4.5 eV. As a specific example, aluminum, calcium, magnesium, silver, cesium (Cs), lithium or alloys containing them may be used. Alternatively, as the organic light emitting device has an n-doped layer as described below, the lower electrode 110 may use a transparent oxide such as ITO (indium tin oxide), IZO (indium zinc oxide) or ZnO (zinc oxide). As a result, light emission may be induced simultaneously to both the lower electrode 110 and the upper electrode 130. The lower electrode 110 may be formed using various known methods, for example, a deposition method, a sputtering method, a spin coating method, or a blade coating method.

The n-doped layer 123 formed on the lower electrode 110 is a layer that generates electrons when a voltage is applied to the device, and the electrons may be injected and transported into the organic light emitting layer 125. When a negative voltage is applied to the lower electrode 230 and a positive electrode is applied to the upper electrode 130, the energy barrier at the interface between the n-doped layer 123 and the lower electrode 110 is lowered, thereby lowering the lower electrode ( Irrespective of the work function value of 110, the injection and transport of electrons can be facilitated.

The n-doped layer 123 may be in the form of a double layer in which a first electron transport layer 123 ″ including a first electron transport material is sequentially stacked on an impurity layer 123 ′ including an n-dopant as an impurity. have. In this case, the energy barrier at the interface between the impurity layer 123 ′ and the lower electrode 110 is lowered, thereby making it easier to inject and transport electrons regardless of the work function value of the lower electrode 110. Alternatively, the n-doped layer 123 may be a single layer containing n-dopant as an impurity in a layer having electron transport characteristics.

The n-dopant is not particularly limited. Examples of n-dopants are lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba) , Metals such as lanthanum (La), cerium (Ce), neodymium (Nd), samarium (Sm), europium (Eu), terbium (Tb), dysprosium (Dy) and ytterbium (Yb), nitrides of the metals, the Carbonates of metals and complexes of the above metals. Preferably, n-dopant is Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , Cs ₂ CO ₃ , Rb ₂ CO ₃ , Ba ₂ CO ₃ , pyronin B, DMC (decamethyl Cobaltocene), BEDTTTF (bis (ethylenedithio) -tetrathiafulvalene), rhodamine B), TMBI (1,2,3-trimethyl-2-phenyl-2,3-dihydro-1H -Benzoimidazole), DMBI (1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzoimidazole), Cl-DMBI (dichlorophenyl-1,3-dimethyl-2,3-di Hydro-1H-benzoimidazole), N-DMBI (4- (1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl) -phenyl) -dimethyl-amine), OH- DMBI (2- (1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl) -phenol), PTCDI-C13 (N, N'-ditridecylperylene-3,4 : 9,10-tetracarboxylic acid diimide) and F-PTCDI-C4 (N, N'-dibutyl-1,7-difluoroperylene-3,4: 9,10-tetracarboxylic acid di Mead) may be used one or more selected from the group consisting of.

As the first electron transport material, a known electron transport material may be used. The first electron transport material is for example B3PYMPM (bis-4,6- (3,5-di-3-pyridylphenyl) -2-methylpyrimidine), Bphen (4,7-diphenyl-1,10 -Phenanthroline), BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), TPBi (2,2 ', 2 "-(1,3,5-benzenetriyl ) -Tris (1-phenyl-1H-benzimidazole), TPQ1 (tris-phenylquinoxalinz 1,3,5-tris [(3-phenyl-6-trifluoromethyl) quinoxalin-2-yl] Benzene), TPQ2 (tris-phenylquinoxalinz 1,3,5-tris [3- (4-tert-butylphenyl) -6-trifluoromethylquinoxalin-2-yl] benzene), TAZ (3- (4-biphenylyl) -4-phenyl-5-tert-butylphenyl-1,2,4-triazole), NTAZ (4- (naphthalen-1-yl) -3,5-diphenyl-4H- 1,2,4-triazole), tBu-PBD (2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole), BeBq2 (10- Benzo [h] quinolinol-beryllium), E3 (terfluorene) or two or more thereof, but are not limited thereto.

The impurity layer 123 'may be formed using a method such as vacuum deposition, sputtering, deposition polymerization, electron beam deposition, plasma deposition, chemical vapor deposition, sol-gel, inkjet printing, spin coating, offset printing, or the like. The first electron transport layer 123 ″ may be formed using a method such as vacuum deposition, spin coating, casting, or LB. The impurity layer 123 'may have a thickness of about 0.2 nm to about 10 nm, Preferably, the thickness may be 0.5 nm to 5 nm, and the thickness of the first electron transport layer 123 ″ may be about 1 nm to about 100 nm, and preferably about 10 nm to about 50 nm. When the thickness of the impurity layer 123 'and the first electron transport layer 123 "satisfies the above range, the level satisfactory by the impurity layer 123' and the first electron transport layer 123" without a substantial increase in driving voltage. Electrons can be generated.

Optionally, the n-doped layer 123 may be formed by doping the n-dopant to the electron transport material. The electron transport material may be an electron transport material used for the first electron transport layer 123 ″, and the n-dopant may be an n-dopant used for the impurity layer 123 ′. The doping concentration may be about 0.1 wt% to 25 wt% based on the total weight of the n-doped layer 123.

The n-doped layer 123 may be formed using various methods such as vacuum deposition, spin coating, casting, or LB. The thickness of the n-doped layer 123 may be about 1 nm to about 100 nm. When the thickness of the n-doped layer 123 satisfies the above range, electrons may be generated to a satisfactory level in the n-doped layer 123 without a substantial increase in driving voltage.

The organic light emitting layer 125 formed on the n-doped layer 123 may be formed using a known phosphorescent host and a phosphorescent dopant, or a known fluorescent host and a fluorescent dopant.

As the known host, for example, Alq3 (tris (8-quinolinorate) aluminum), CBP (4,4'-N, N'-dicarbazole-biphenyl), mCP (1,3-bis (carba) Sol-9-yl) benzene), ADN (9,10-di-naphthalen-2-yl-anthracene), PVK (poly (n-vinylcarbazole)), TCTA, TPBI (1,3,5-tris ( N-phenylbenzimidazol-2-yl) benzene), TBADN (3-tert-butyl-9,10-di (naphth-2-yl) anthracene), or E3, etc. may be used, but is not limited thereto. no.

PtOEP (Pt (II) octaethylformine), Ir (piq) ₃ (tris (2-phenylisoquinoline) iridium (III)), Ir (Mphq) ₃ (tris (2-phenyl-4-methyl) as red dopant Quinoline) iridium (III)), Btp ₂ Ir (acac) (bis (2- (2'-benzothienyl) -pyridinato-N, C3 ') iridium (acetylacetonate)), DCM (4- ( Dicyanomethylene) -2-methyl-6- [p- (dimethylamino) styryl] -4H-pyran) or DCJTB (4- (dicyanomethylene) -2-tert-butyl-6- (1,1, 7,7, -tetramethyljurrolidyl-9-enyl) -4H-pyran) and the like, but is not limited thereto.

Ir (ppy) ₃ (tris (2-phenylpyridine) iridium (III)), Ir (ppy) ₂ (acac) (bis (2-phenylpyridine) (acetylaceto) iridium (III)), or Ir as green dopant (mpyp) ₃ (tris (2- (4-tolyl) phenylpyridine) iridium (III)), C545T (10- (2-benzothiazolyl) -1,1,7,7-tetramethyl-2,3, 6,7, -tetrahydro-1H, 5H, 11H- [1] benzopyrano [6,7,8-ij] -quinolizine-11-one) and the like, but is not limited thereto.

Further, as a blue dopant, FIrPic (bis (3,5-difluoro-2- (2-pyridyl) phenyl- (2-carboxypyridyl) iridium (III)), (F ₂ ppy) ₂ Ir (tmd) ), Ir (dfppz) ₃ , DPVBi (4,4'-bis (2,2'-diphenylethen-1-yl) biphenyl), DPAVBi (4,4'-bis (4-diphenylaminostar Aryl) biphenyl), or TBPe (2,5,8,11-tetra- tert -butyl perylene) and the like, but is not limited thereto.

When the organic light emitting layer 125 includes a host and a dopant, the content of the dopant may be generally selected from about 0.01 to about 25 parts by weight based on about 100 parts by weight of the host, but is not limited thereto.

The organic light emitting layer 125 may have a thickness of about 10 nm to about 50 nm. When the thickness of the organic light emitting layer 125 satisfies the above range, the organic light emitting layer 125 may exhibit excellent light emission characteristics without substantially increasing the driving voltage.

As a material for forming the hole transport layer 126 formed on the organic light emitting layer 125, NPB (4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl), TPD (4, 4'-bis [N- (3-methylphenyl) -N-phenylamino] biphenyl), MTDATA (4,4 ', 4 "-tris [(3-methylphenyl) phenylamino] triphenylamine), TAPC (1 , 1-bis (4- (N, N-di-p-tolylamino) phenyl) cyclohexane), TCTA (4- (9H-carbazol-9-yl) -N, N-bis [4- ( 9H-carbazol-9-yl) phenyl] -benzeneamine), CBP (9,9 '-[1,1'-biphenyl] -4,4'-diylbis-9H-carbazole) and 2- At least 1 sort (s) of TNATA (4,4 ', 4 "-tris (N- (2-naphthyl) -N-phenylamino) triphenylamine) is mentioned.

The hole transport layer 126 may be formed using various methods such as vacuum deposition, spin coating, casting, or LB. The hole transport layer 126 may have a thickness of about 1 nm to about 100 nm. When the thickness of the hole transport layer 126 satisfies the above range, a satisfactory hole transport characteristic may be obtained without a substantial increase in driving voltage.

The hole injection layer 127 formed on the hole transport layer 126 is preferably formed of a layer made of a single undoped material. The use of a layer of a single material can prevent damage to the organic layer while maintaining a satisfactory level of hole injection characteristics without a substantial increase in driving voltage.

The hole injection layer 127 may include a crystalline organic compound of Formula 1 below.

[Formula 1]

In Formula 1, R is cyano (-CN), nitro (-NO ₂ ), phenylsulfonyl (-SO2 (C6H5)), cyano or nitro substituted C ₂ to C ₅ alkenyl, and cyano or nitro It is selected from the group consisting of phenyl substituted with.

The crystalline organic compound of Formula 1 is preferably HAT-CN (hexaazatriphenylene hexacarbonitrile) of the following formula.

The crystalline organic compound in the hole injection layer 127 exhibits lattice, that is, crystallization, so that the hole injection layer 127 may have mechanical strength. Therefore, when the upper electrode 130 is formed by sputtering, the hole injection layer 127 may protect the lower organic layer from impact damage that may occur during the formation of the upper electrode 130. Thus, a transparent electrode can be used as the upper electrode.

The hole injection layer 127 may be formed using various methods such as vacuum deposition, spin coating, casting, or LB. The hole injection layer 127 may have a thickness of about 1 nm to about 1,000 nm. When the thickness of the hole injection layer 127 satisfies the above range, a satisfactory hole injection characteristic may be obtained without a substantial increase in driving voltage, and the lower organic layer may be protected when the upper electrode 130 is formed.

The upper electrode 130 formed on the hole injection layer 127 may be formed as a transparent electrode for top emission. For example, the upper electrode 130 may be formed using a transparent metal oxide such as ITO (indium tin oxide), IZO (indium zinc oxide), ZnO (zinc oxide), or SnO ₂ (tin oxide).

The capping layer 141 formed on the upper electrode 130 has a refractive index of less than 1.0 to 2.0. The capping layer 141 having the refractive index in this range is formed on the upper electrode 130 to view the viewing angle in the conventional organic light emitting device. Accordingly, a wide viewing angle can be obtained by reducing a phenomenon in which the spectrum of light emitted is changed, and the light efficiency of the organic light emitting device is excellent. The lower the refractive index is, the more preferable. Specifically, the refractive index may be in the range of 1.2 to 1.5.

In addition, since the capping layer 141 is formed on the upper electrode 130, the capping layer 141 preferably has a low light absorption, and preferably has a transmittance of more than 50% at a wavelength in the visible light region, and a transmittance of more than 80%. More preferred.

The material of the capping layer 141 is not particularly limited as long as it satisfies the conditions of the refractive index and the transmittance. For example, the material of the capping layer 141 may be at least one selected from the group consisting of fluoride compounds, specifically, LiF, MgF ₂ , CaF _2, and ScF ₃ . In addition, the capping layer 141 may satisfy the low refractive index by including particles having a size smaller than the wavelength of light emitted from the organic layer. Examples of particles that may be used in the present embodiment include titanium dioxide (TiO ₂ ). , Inorganic particles such as silica (SiO ₂ ), alumina (Al ₂ O ₃ ), aluminum hydroxide (Al (OH) ₃ ), aluminum, nickel, copper, silver and gold and silicon beads, styrene beads, PMMA (polymethylmetha Organic particles such as acrylate) beads, PU (polyurethane) beads, and PBMA (polybutyl methacrylate) beads. The inorganic particles and / or the organic particles may be used together with the fluoride compound, or may be used together with a dielectric compound such as Alq ₃ or a binder resin.

Although the capping layer 141 may be a single layer, the capping layer 141 may include two or more layers having different refractive indices so that the refractive index may gradually change while passing through the two or more layers.

The thickness of the capping layer 141 may be 20 to 120 nm. The capping layer 141 may be formed to have a substantially similar thickness regardless of whether the organic light emitting diode emits red, green, or blue light. Preferably, when the organic light emitting layer 125 is a blue or red organic light emitting device 100 including a blue dopant or a red dopant, the thickness of the capping layer 141 may be 70 to 90 nm, and the organic light emitting layer When the 125 is a green organic light emitting diode 100 including a green dopant, the capping layer 141 may have a thickness of about 90 nm to about 120 nm. The capping layer 141 may be formed using various methods such as vacuum deposition, spin coating, casting, or LB.

Hereinafter, a method of manufacturing the organic light emitting diode 100 will be described in detail with reference to FIG. 1.

The organic light emitting diode 100 according to the embodiment may include providing a substrate 101, forming a lower electrode 110 on the substrate 101, and an n-doped layer on the lower electrode 110. Forming an organic layer 120 including an organic light emitting layer 125, a hole transport layer 126, and a hole injection layer 127 including a crystalline compound, and a transparent upper electrode on the organic layer 120. Forming a capping layer 141 having a refractive index of less than 1.2 to 2 on the upper electrode 130.

According to another aspect of the present invention, there is provided a display device including the organic light emitting device described above. Specifically, the display device includes a substrate, an n-type thin film transistor formed on the substrate and including a source electrode, a drain electrode, an oxide semiconductor layer, a gate electrode, and a gate insulating layer; An insulation layer formed on the n-type thin film transistor; And an organic light emitting diode as described above formed on the insulating layer, wherein the lower electrode of the organic light emitting diode is electrically connected to one of the source electrode and the drain electrode.

The display device is excellent in luminous efficiency and may be usefully used in flexible organic light emitting display devices and lighting, which have recently emerged in the display field.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited to the examples.

Example 1 Fabrication of Blue Organic Light-Emitting Device Having a Capping Layer

A transparent glass substrate was prepared, and aluminum (Al) was vacuum deposited on the glass substrate to form a lower electrode having a thickness of 100 nm. Cs ₂ CO ₃ was vacuum deposited on the lower electrode to form an impurity layer having a thickness of 1 nm, and B3PYMPM was vacuum deposited on the impurity layer to form a first electron transport layer having a thickness of 35 nm. TPBi was vacuum deposited on the first electron transport layer to form a second electron transport layer having a thickness of 15 nm. MCP and FIrPic were co-deposited on the second electron transport layer at a weight ratio of 90:10 to form a light emitting layer having a thickness of 15 nm. TAPC was vacuum-deposited on the emission layer to form a hole transport layer having a thickness of 20 nm. HAT-CN was vacuum deposited on the hole transport layer to form a hole injection layer having a thickness of 50 nm, and then an upper electrode having a thickness of 60 nm was formed by sputter deposition of IZO. LiF (refractive index = 1.39) was vacuum deposited on the IZO upper electrode to form a capping layer having a thickness of 80 nm, thereby manufacturing a blue organic light emitting device having a capping layer.

Comparative Example 1 Fabrication of a Blue Organic Light-Emitting Device Without a Capping Layer

A blue organic light emitting diode was manufactured according to the same method as Example 1 except that the capping layer of LiF was not formed on the IZO upper electrode.

Example 2 Fabrication of Green Organic Light Emitting Diode with Capping Layer

A transparent glass substrate was prepared, and aluminum (Al) was vacuum deposited on the glass substrate to form a lower electrode having a thickness of 100 nm. Cs ₂ CO ₃ was vacuum deposited on the lower electrode to form an impurity layer having a thickness of 1 nm, and B3PYMPM was vacuum deposited on the impurity layer to form a first electron transport layer having a thickness of 45 nm. TPBi was vacuum deposited on the first electron transport layer to form a second electron transport layer having a thickness of 15 nm. CBP and Ir (ppy) ₃ were co-deposited on the second electron transport layer at a weight ratio of 92: 8 to form a light emitting layer having a thickness of 15 nm. TAPC was vacuum deposited on the emission layer to form a hole transport layer having a thickness of 40 nm. HAT-CN was vacuum deposited on the hole transport layer to form a hole injection layer having a thickness of 50 nm, and then an upper electrode having a thickness of 60 nm was formed by sputter deposition of IZO. LiF (refractive index = 1.39) was vacuum deposited on the IZO upper electrode to form a capping layer having a thickness of 100 nm, thereby manufacturing a green organic light emitting device having a capping layer.

Comparative Example 2 Fabrication of Green Organic Light-Emitting Device Without Capping Layer

A green organic light emitting diode was manufactured according to the same method as Example 2 except for forming a capping layer of LiF on the IZO upper electrode.

Example 3 Fabrication of Red Organic Light Emitting Diode with Capping Layer

A transparent glass substrate was prepared, and aluminum (Al) was vacuum deposited on the glass substrate to form a lower electrode having a thickness of 100 nm. Cs ₂ CO ₃ was vacuum deposited on the lower electrode to form an impurity layer having a thickness of 1 nm, and B3PYMPM was vacuum deposited on the impurity layer to form a first electron transport layer having a thickness of 60 nm. TPBi was vacuum deposited on the first electron transport layer to form a second electron transport layer having a thickness of 15 nm. CBP and Ir (Mphq) ₃ were co-deposited on the second electron transport layer at a weight ratio of 95: 5 to form a light emitting layer having a thickness of 15 nm. TAPC was vacuum-deposited on the emission layer to form a hole transport layer having a thickness of 60 nm. HAT-CN was vacuum deposited on the hole transport layer to form a hole injection layer having a thickness of 50 nm, and then an upper electrode having a thickness of 60 nm was formed by sputter deposition of IZO. LiF (refractive index = 1.39) was vacuum deposited on the IZO upper electrode to form a capping layer having a thickness of 80 nm, thereby manufacturing a red organic light emitting device having a capping layer.

Comparative Example 3 Fabrication of Red Organic Light-Emitting Device Without Capping Layer

A red organic light emitting diode was manufactured according to the same method as Example 3 except that the capping layer of LiF was not formed on the IZO upper electrode.

Evaluation Example 1-Viewing Angle Evaluation

The emission spectrum of the organic light emitting element was measured using a spectrophotometer while changing the viewing angle in steps from 0 ° to 60 °, and the color coordinate value was calculated from this measured value.

The emission spectra of Comparative Example 1 and Example 1 are shown in Figs. 2A and 2B, respectively, and their color coordinate values are also shown in Fig. 3. The emission spectra of Comparative Example 2 and Example 2 are shown in Figs. 4A and 4B, respectively, and their color coordinate values are shown in Fig. 5. The emission spectra of Comparative Example 3 and Example 3 are shown in Figs. 6A and 6B, respectively, and their color coordinate values are shown in Fig. 7.

According to these FIGS. 2 to 7, in the case of the organic light emitting device without the capping layer, the variation in the emission spectrum and the color coordinate values is severely varied according to the change of the viewing angle from 0 ° to 60 °, whereas in the case of the organic light emitting device having the capping layer In this way, it can be seen that the emission spectrum and the color coordinate value remain almost constant without changing the viewing angle. This means that using the organic light emitting device having a capping layer according to the present invention can significantly improve the characteristics of the viewing angle.

[Evaluation Example 2]-Light Efficiency Variation According to Refractive Index and Thickness of Capping Layer

Simulation results were obtained using the green organic light emitting diode fabricated in Example 2 in order to investigate the change in the light efficiency according to the change in the refractive index and the thickness of the capping layer. In FIG. 8, the refractive index and the thickness of the capping layer were varied in the range of 1.4 to 2.5 and the range of 0 to 200 nm, respectively, and the light efficiency was expressed as a value of quantum yield.

In FIG. 8, the lower the refractive index of the capping layer is always excellent regardless of the thickness, the higher the refractive index, the higher the refractive index, it can be seen that the light efficiency significantly decreases even in the difference of the small thickness.

Evaluation Example 3 Evaluation of Viewing Angle When High Refractive Index Capping Layer was Used

Although the refractive index of the capping layer is high in FIG. 8, it can be seen that the light efficiency is good when the thickness is thin. Therefore, in order to find out whether the viewing angle can be improved even when the capping layer is made of a material having a high refractive index, the green organic light emitting device manufactured in Example 2 is used, but the material of the refractive index 2.4 is used and the thickness is 5 nm, With the capping layers of 10 nm, 15 nm and 20 nm, the emission spectrum of the organic light emitting device was obtained as a simulation result when the viewing angle was changed stepwise from 0 ° to 60 °, and the results were shown in FIGS. 9A (thickness 5 nm) and 9b ( Thickness 10 nm), 9c (thickness 15 nm) and 9d (thickness 20 nm). In addition, color coordinate values were obtained from the emission spectra of FIGS. 9A to 9D and the emission spectrum of FIG. 4B obtained from the organic light emitting diode of Example 2, and are shown in FIG. 10.

According to these FIGS. 9A to 9D and 10, in the case of the organic light emitting device using the high refractive index capping layer, even if the thickness is thin, the emission spectrum and the color coordinate value are severely shown. This means that if the refractive index of the capping layer is high, even if the light efficiency is kept good, the improvement of the viewing angle according to the use of the capping layer does not appear.

The invention of the present application is applicable to an organic light emitting device and the field using the same.

Claims (14)

1. Board;

   A lower electrode formed on the substrate;

   An n-doped layer formed on the lower electrode, an organic light emitting layer formed on the n-doped layer, a hole transport layer formed on the organic light emitting layer, and a hole injection layer formed on the hole transport layer and including a crystalline organic compound An organic layer comprising a layer;

   A transparent upper electrode formed on the organic layer; And

   And a capping layer formed on the transparent upper electrode, wherein the capping layer has a refractive index of 1.0 to less than 2.0.
2. The organic light emitting device of claim 1, wherein the capping layer has a refractive index of about 1.2 to about 1.5.
3. The organic light emitting device of claim 1, wherein the capping layer comprises a fluoride compound.
4. The organic light emitting device of claim 1, wherein the fluoride compound is at least one selected from the group consisting of LiF, MgF ₂ , CaF _2, and ScF ₃ .
5. The organic light emitting device of claim 1, wherein the capping layer includes particles having a size smaller than a wavelength of light emitted from the organic layer.
6. The organic light emitting diode of claim 1, wherein the capping layer comprises two or more layers having different refractive indices.
7. The organic light emitting device of claim 1, wherein the capping layer has a thickness of about 20 nm to about 120 nm.
8. The method of claim 1, wherein the n-doped layer comprises an n- dopant, the n- dopant is Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , Cs ₂ CO ₃ , Rb ₂ CO ₃ , Ba ₂ CO ₃ , pyronin B, DMC (decamethylcobaltocene), BEDTTTF (bis (ethylenedithio) -tetrathiafulvalene), rhodamine B (rhodamin B), TMBI (1,2, 3-trimethyl-2-phenyl-2,3-dihydro-1H-benzoimidazole), DMBI (1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzoimidazole), Cl- DMBI (dichlorophenyl-1,3-dimethyl-2,3-dihydro-1H-benzoimidazole), N-DMBI (4- (1,3-dimethyl-2,3-dihydro-1H-benzoimidazole -2-yl) -phenyl) -dimethyl-amine), OH-DMBI (2- (1,3-dimethyl-2,3-dihydro-1 H-benzoimidazol-2-yl) -phenol), PTCDI- C13 (N, N'-ditridecyl perylene-3,4: 9,10-tetracarboxylic acid diimide) and F-PTCDI-C4 (N, N'-dibutyl-1,7-difluoro Perylene-3,4: 9,10-tetracarboxylic acid diimide).
9. The organic light emitting device of claim 8, wherein the n-doped layer includes an impurity layer including an n-dopant and a first electron transport layer including a first electron transport material formed on the impurity layer.
10. The organic light emitting device of claim 1, wherein the crystalline organic compound is represented by the following Chemical Formula 1:

     [Formula 1]

    

    In Formula 1, R is cyano (-CN), nitro (-NO2), phenylsulfonyl (-SO2 (C6H5)), C2 to C5 alkenyl substituted with cyano or nitro, and cyano or nitro substituted It is selected from the group consisting of phenyl.
11. The organic light-emitting device according to claim 10, wherein the crystalline organic compound is HAT-CN (hexaazatriphenylene hexacarbonitrile).
12. The organic light emitting device of claim 1, wherein the upper electrode comprises ITO (indium tin oxide), IZO (indium zinc oxide), ZnO (zinc oxide), or SnO ₂ (tin oxide).
13. A display device comprising the organic light emitting device according to any one of claims 1 to 12.
14. An illumination comprising the organic light emitting element according to any one of claims 1 to 12.

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