KR20190014460A - Organic light-emitting device - Google Patents

Abstract

Disclosed is an organic light emitting device, which comprises: a first electrode; a second electrode; and an organic layer interposed between the first and second electrodes. The organic layer includes a light emitting layer. The light emitting layer includes first to third compounds, wherein the first to third compounds satisfy equations 1 to 3, which are ¦H_(HOMO) - SD_(HOMO)¦>= 0.1 eV, μ_(SD) >= 3.2 debye, and H_(S1) > SD_(S1) > FD_(S1). In the equations 1 to 3, H_(HOMO) is the highest occupied molecular orbital energy level of the first compound, SD_(HOMO) is the highest occupied molecular orbital energy level of the second compound, μ_(SD) is a dipole moment value of the second compound, H_(S1) is the lowest excitation singlet energy level of the first compound, SD_(S1) is the lowest excitation singlet energy level of the second compound; and FD_(S1) is the lowest excitation singlet energy level of the first compound.

Description

Organic light-emitting device

And an organic light emitting device.

An organic light-emitting device is a self-luminous device that emits light by itself using an electroluminescent phenomenon that emits light when an electric current flows through an organic compound.

The organic light emitting device may have a structure in which an organic layer including a light emitting layer and a second electrode are sequentially formed on the first electrode. Holes injected from the first electrode and electrons injected from the second electrode may move to the light emitting layer. Carriers such as holes and electrons may recombine in the light emitting layer region to generate excitons. This exciton changes from the excited state to the ground state and light is generated.

The organic light emitting device emitting fluorescence has a relatively low internal quantum efficiency as compared with the organic light emitting device emitting phosphorescence and the organic light emitting device emitting phosphorescence has a disadvantage that the lifetime is relatively short as compared with the organic light emitting device emitting fluorescence . Therefore, there is a need to develop an organic light emitting device having improved both internal quantum efficiency and lifetime.

Embodiments of the present invention provide an organic light emitting device. Specifically, an organic light emitting device having improved internal quantum efficiency and lifetime is provided.

According to an aspect of the present invention, there is provided a plasma display panel comprising: a first electrode; A second electrode; And an organic layer interposed between the first electrode and the second electrode; Wherein the organic layer comprises a light emitting layer; Wherein the light emitting layer comprises a first compound, a second compound and a third compound; Wherein the first compound, the second compound and the third compound satisfy the following formulas 1 to 3:

<Formula 1>

│H _HOMO - SD _HOMO │≥ 0.1 eV

<Formula 2>

μ _SD ≥ 3.2 ball

<Formula 3>

H _S1 > SD _S1 > FD _S1

Of the above formulas 1 to 3,

H _HOMO is the highest level occupied molecular orbital energy level of the first compound, SD _HOMO is the highest level occupied molecular orbital energy level of the second compound,

μ _SD is the dipole moment value of the second compound,

H _S1 is the lowest excited singlet energy level of the first compound, SD _S1 is the lowest excited singlet energy level of the second compound, and FD _S1 is the lowest excited singlet energy level of the first compound.

In the present embodiment, the third compound may further satisfy the following formula 4:

<Formula 4>

μ _FD ≤ 2.0 debuggers

In the formula 4,

and μ _FD is the dipole moment value of the third compound.

In the present embodiment, the first compound, the second compound and the third compound satisfy the following formulas 1 and 2-1; The first compound, the second compound and the third compound may satisfy the following formulas 1-1 and 2:

<Formula 1>

│H _HOMO - SD _HOMO │≥ 0.1 eV

<Expression 1-1>

│H _HOMO - SD _HOMO │≥ 0.3 eV

<Formula 2>

μ _SD ≥ 3.2 ball

<Formula 2-1>

μ _SD ≥ 6.0 ball

Of the above-mentioned formulas 1, 1-1, 2 and 2-1,

H _HOMO is the highest level occupied molecular orbital energy level of the first compound, SD _HOMO is the highest level occupied molecular orbital energy level of the second compound,

and μ _SD is the dipole moment value of the second compound.

In this embodiment, the molar concentration of the first compound may be greater than or equal to the molar concentration of the second compound and the molar concentration of the third compound.

In this embodiment, the molar concentration of the second compound may be greater than or equal to the molar concentration of the third compound.

In the present embodiment, the second compound may include a metal atom having an atomic weight of 40 or more.

In the present embodiment, the second compound may be a homoleptic organometallic compound.

In this embodiment, the third compound may emit light.

In the present embodiment, the light emitting layer may further include a fourth compound.

In the present embodiment, the first compound and the fourth compound may form an exiflex.

The organic light emitting device according to an embodiment of the present invention has improved internal quantum efficiency and lifetime.

1 is a cross-sectional view schematically showing the structure of an organic light emitting diode according to an embodiment of the present invention.
2 is B3PYMPM, TCTA, Ir (ppy) 2 (acac), Ir (mpp) 2 (acac), Ir (ppy) 2 (tmd), Ir (ppy) 3, Ir (mppy) 3 and Ir (chpy) _{3 shows} the HOMO energy level and the LUMO energy level.
Figures 3 to 6 show the current density-drive voltage (JV), the luminance-drive voltage (LV), the luminance-drive voltage and the luminance-external quantum efficiency, respectively, for Reference Examples 1 to 3 and Comparative Reference Examples 1 to 3 And the results are shown in Fig.
7 is a diagram showing transition EL data for Reference Examples 1 to 3 and Comparative Reference Examples 1 to 3. Fig.
8 is _{Ir (ppy) 2 (tmd)} , Ir (ppy) 2 (acac), Ir (mppy) 2 (acac), Ir (ppy) 3, Ir (mppy) 3 , and Fig. 4 is a graph showing the ratio of rejuvenation of the total re-combination to the trap radius or dipole moment and trap depth for Ir (chpy) ₃ .

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, like reference numerals refer to like elements.

1 is a cross-sectional view schematically showing a structure of an organic light emitting diode 10 according to an embodiment of the present invention.

The organic light emitting device 10 includes a first electrode 11; A second electrode 19; And an organic layer (15) interposed between the first electrode (11) and the second electrode (19); The organic layer 15 comprises a light emitting layer 16; The light-emitting layer (16) is characterized in that the light-emitting layer comprises a first compound, a second compound and a third compound; The first compound, the second compound and the third compound may satisfy the following formulas 1 to 3:

<Formula 1>

│H _HOMO - SD _HOMO │≥ 0.1 eV

<Formula 2>

μ _SD ≥ 3.2 ball

<Formula 3>

H _S1 > SD _S1 > FD _S1

Of the above formulas 1 to 3,

H _HOMO is the highest level occupied molecular orbital energy level of the first compound, SD _HOMO is the highest level occupied molecular orbital energy level of the second compound,

μ _SD is the dipole moment value of the second compound,

H _S1 is the lowest excited singlet energy level of the first compound, SD _S1 is the lowest excited singlet energy level of the second compound, and FD _S1 is the lowest excited singlet energy level of the first compound.

When the organic light emitting device satisfies the above formulas 1 to 3, the triplet yield of the organic light emitting device can be increased. Specifically, the direct charge trapping from the first compound to the third compound can be reduced. On the other hand, the trap assisted recombination ratio of the first compound and the second compound may become dominant and the charge trapping from the second compound to the third compound may increase after the reverse-intercalation transition in the second compound have. Accordingly, the internal light emitting efficiency can be improved to nearly 100%, and the organic light emitting device having the advantages of the fluorescent organic light emitting device can be provided while solving the drawbacks of the conventional fluorescent organic light emitting device, while maintaining the color purity and lifetime.

For example, the third compound may more satisfactorily satisfy the following formula 4, but is not limited thereto:

<Formula 4>

μ _FD ≤ 2.0 debuggers

In the formula 4,

and μ _FD is the dipole moment value of the third compound.

For example, the first compound and the second compound may satisfy the following formula 1-1, but are not limited thereto:

<Expression 1-1>

│H _HOMO - SD _HOMO │≥ 0.3 eV

In the formula 1-1,

H _HOMO is the highest level occupied molecular orbital energy level of the first compound and SD _HOMO is the highest level occupied molecular orbital energy level of the second compound.

When the first compound and the second compound satisfy Formula 1-1, the trap assisted recombination ratio of the first compound and the second compound may become higher, and thus the internal quantum efficiency Can be improved.

As another example, the second compound may satisfy the following formula 2-1, but is not limited thereto:

<Formula 2-1>

μ _SD ≥ 6.0 ball

In the formula 2-1,

and μ _SD is the dipole moment value of the second compound.

When the second compound satisfies the formula 2-1, the trap assisted recombination ratio of the first compound and the second compound may become higher, thereby improving the internal quantum efficiency of the organic light emitting device .

As another example, the first compound and the second compound satisfy the following formulas 1 and 2-1; The following formulas 1-1 and 2 can be satisfied, but are not limited thereto:

<Formula 1>

│H _HOMO - SD _HOMO │≥ 0.1 eV

<Expression 1-1>

│H _HOMO - SD _HOMO │≥ 0.3 eV

<Formula 2>

μ _SD ≥ 3.2 ball

<Formula 2-1>

μ _SD ≥ 6.0 ball

Of the above-mentioned formulas 1, 1-1, 2 and 2-1,

H _HOMO is the highest level occupied molecular orbital energy level of the first compound, SD _HOMO is the highest level occupied molecular orbital energy level of the second compound,

and μ _SD is the dipole moment value of the second compound.

When the first compound and the second compound satisfy the formulas 1 and 2-1 or satisfy the expressions 1-1 and 2, the trap assisted recombination ratio of the first compound and the second compound is higher And thus the internal quantum efficiency of the organic light emitting device can be improved.

In one embodiment, the first compound may not emit light.

For example, the first compound may act as a host, but is not limited thereto.

In one embodiment, the first compound may use a known host.

For example, the first compound may be selected from a carbazole-containing compound, an aromatic amine compound, a? -Electron deficient complex aromatic compound, a phosphine oxide-containing compound, and a sulfur oxide-containing compound.

As another example, the first compound may be selected from the group consisting of mCP (1,3-bis (9-carbazolyl) benzene), TCTA (4-carbazoyl- carbazolyl) -1,1'-biphenyl), mCBP (3,3-bis (carbazol-9-yl) biphenyl), NPB (N, N'-di (1-naphthyl) -N, Diamine), m-MTDATA (4,4 ', 4 "-tris [phenyl (m-tolyl) amino] triphenylamine), TPD (N, N'-bis 3-methylphenyl) -N, N'-diphenylbenzidine), B3PYMPM (bis-4,6- (3,5-di-3-pyridylphenyl) -2-methylpyrimidine dine), B4PYMPM , 5-di-4-pyridylphenyl) -2-methylpyrimidine-dine) TPBi (2,2 ', 2 "- (1,3,5-benzenetriyl) tris- Tris (2,4,6-trimethyl-3- (pyridin-3-yl) phenyl) borane), BmPyPB (1,3-bis [ (3,3'- [5 '- [3- (3-Pyridinyl) phenyl] [1,1': 3 ', 1 "-terphenyl] -3,3" -diyl] bispyridine, the following compound BSFM The compound PO-T2T PO15 (dibenzo [b, d] thiophene-2,8-diylbis (diphenylphosphine oxide)), DPEPO (bis [2- (diphenylphosphino) phenyl] ether oxide) and TSPO1 (diphenyl-4-triphenylsilylphenyl-phosphine oxide, for example, but are not limited to:

In one embodiment, the molar concentration of the first compound may be greater than or equal to the molarity of the second compound and the molarity of the third compound, but is not limited thereto.

For example, the content of the first compound may be about 97 wt% to about 50 wt% based on the total weight of the light emitting layer, but is not limited thereto.

As another example, the content of the first compound may be about 95 wt% or less, about 90 wt% or less, about 85 wt% or less, about 60 wt% or more, about 70 wt% or more based on the total weight of the light emitting layer, or But it is not limited thereto.

In one embodiment, the second compound may not emit light.

For example, the second compound may act as an auxiliary dopant, but is not so limited.

In one embodiment, the second compound may use known phosphorescent dopants and / or retarded fluorescent dopants.

In one embodiment, the second compound may include, but is not limited to, metal atoms having an atomic weight of 40 or more. Specifically, the second compound may be at least one selected from the group consisting of Ir, Pt, Os, Ru, Rh, Pd, Cu, But not limited to, Au, Ti, Zr, Hf, Eu, Terbium, or Tm.

In one embodiment, the second compound may be a homoleptic organometallic compound, but is not limited thereto.

In one embodiment, the second compound may be represented by the following formula (4), but is not limited thereto:

&Lt; Formula 4 >

M (L ₄₁ ) ₃

<Formula 4-1>

Of the above formulas (4) and (4-1)

M is at least one selected from the group consisting of Ir, Pt, Os, Ru, Rh, Pd, Cu, Ag, ), Zirconium (Zr), hafnium (Hf), europium (Eu), terbium (Tb) and thorium (Tm)

L ₄₁ is selected from the ligands represented by the above formula (4-1), the three L _{41 s} are the same,

X ₄₁ to X ₄₄ independently of one another are nitrogen or carbon,

X ₄₁ and X ₄₃ are connected through a single bond or a double bond, X ₄₂ and X ₄₄ are connected through a single bond or a double bond,

A ₄₁ and A ₄₂ are independently of each other a C ₅ -C ₆₀ carbocyclic group or a C ₁ -C ₆₀ heterocyclic group,

X ₄₅ is a single bond, * -O- * ', * -S- *', * -C (= O) - * ', * -N (Q 41) - *', * -C (Q 41) ( _{and, * -C (Q 41) =} * ' or _{* = C (Q 41) =} *', Q 42) - - * '*, * -C (Q 41) = C (Q 42)'

X ₄₆ and X ₄₇ are independently of each other a single bond, O or S,

R ₄₁ and R ₄₂ independently represent hydrogen, deuterium, -F, -Cl, -Br, -I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, A substituted or unsubstituted C ₁ -C ₂₀ alkyl group, a substituted or unsubstituted C ₁ -C ₂₀ alkoxy group, a substituted or unsubstituted C ₃ -C ₁₀ cycloalkyl group, a substituted or unsubstituted C ₁ -C ₁₀ heterocycloalkyl group, a substituted or unsubstituted C ₃ -C ₁₀ cycloalkenyl group, a substituted or unsubstituted C ₁ -C ₁₀ heteroaryl cycloalkenyl group, a substituted or unsubstituted C ₆ -C ₆₀ aryl group, a substituted or unsubstituted C ₆ ring - C ₆₀ aryloxy group, a substituted or unsubstituted C ₆ -C ₆₀ arylthio group, a substituted or unsubstituted C ₁ -C ₆₀ heteroaryl group, a substituted or unsubstituted 1, a non-condensed polycyclic aromatic group and a substituted or (Q ₄₁ ) (Q ₄₂ ) (Q ₄₃ ), -N (Q ₄₁ ) (Q ₄₂ ), -B (Q ₄₁ ) (Q ₄₂ ), and the unsubstituted monovalent non-aromatic heterocyclic polycyclic group, (Q ₄₁ ), -S (= O) ₂ (Q ₄₁ ), and -P (= O) (Q ₄₁ (Q ₄₂ ), and Q ₄₀₁ to Q ₄₀₃ are independently selected from a C ₁ -C ₁₀ alkyl group, a C ₁ -C ₁₀ alkoxy group, a C ₆ -C ₂₀ aryl group and a C ₁ -C ₂₀ heteroaryl Lt; / RTI &gt;

b41 and b42 are each independently selected from an integer of 0 to 10,

Q ₄₁ to Q ₄₃ are hydrogen, deuterium, C ₁ -C ₂₀ alkyl group, C ₁ -C ₂₀ alkoxy group, phenyl group, biphenyl group, terphenyl group or naphthyl group,

* And * are the binding sites for M in the above formula (4).

According to one embodiment, A ₄₁ and A ₄₂ in the above formula (4-1) independently represent a cyclopentane group, a cyclohexane group, a benzene group, a naphthalene group, a fluorene group, a spirobifluorene group, , Pyrrole group, thiophene group, furan group, imidazole group, pyrazole group, thiazole group, isothiazole group, oxazole group, isoxazole group, pyridine group, pyrazine group, pyrimidine group, pyridazine group, A quinoxaline group, a quinoxaline group, a quinazoline group, a carbazole group, a benzimidazole group, a benzofuran group, a benzothiophene group, an isobenzothiophene group, a benzoxazole group, an isobenzoyl group, An oxazole group, a triazole group, a tetrazole group, an oxadiazole group, a triazine group, a dibenzofuran group and a dibenzothiophene group.

According to another embodiment, i) X ₄₁ in the formula 4-1 is nitrogen and X ₄₂ is carbon, or ii) both X ₄₁ and X ₄₂ may be nitrogen.

Alternatively, the second compound is _{Ir (ppy) 3, Ir (} mppy) 3, Ir (pmi) 3, Ir (pmb) 3, Ir (chpy) 3, Ir (ppz) 3 and Ir (dfppz) ₃ selected from But is not limited thereto.

In one embodiment, the second compound may be represented by any one of the following Formulas 1 to 3, but is not limited thereto:

&Lt; Formula 1 >

D-C-A

(2)

D-C-A-C-D

(3)

A-C-D-C-A

Among the above formulas (1) to (3)

D is an electron donation group;

C is a connection group;

A is an electron accepting group.

D-C-A is a compound of the structure in which D is connected to A through C; Similarly, the second compounds of the above formulas (2) and (3) can be interpreted as the second compound of the above formula (1).

For example, D may include, but is not limited to, a carbazole group, a phenoxazinyl group, a phenothiazinyl group, a dibenzoazasilinanyl group, or an aromatic amine group.

For example, A may include a cyano group, -F, a phenyl group substituted with a cyano group, a phenyl group substituted with -F, a pyridyl group, a pyrrolyl group, a triazinyl group, a carbonyl group, a phosphine oxide group or a sulfuric oxide group However, the present invention is not limited thereto.

For example, C may include, but is not limited to, an arylene group such as a phenylene group or a naphthylenyl group.

According to the structures of Formulas 1 to 3, D, A, and C may be 1 or 2, respectively.

As another example, the second compound may include, but is not limited to, 4CzIPN, 2CzPN, 4CzTPN-Ph, PXZ-DPS, DTPPDDA, BDAPM,

In one embodiment, the molar concentration of the second compound may be greater than or equal to the molar concentration of the third compound, but is not limited thereto.

For example, the content of the second compound may be about 1% by weight to about 30% by weight based on the total weight of the light emitting layer, but is not limited thereto.

As another example, the content of the second compound may be about 7 wt% to about 15 wt%, or about 10 wt%, based on the total weight of the light emitting layer, but is not limited thereto.

In one embodiment, the third compound is capable of emitting light, but is not limited thereto. Here, the third compound may act as a dopant.

For example, the third compound may emit fluorescence, but is not limited thereto. The fact that the third compound emits fluorescence means that electrons are transferred to the base energy level at the lowest excitation energy level of the third compound to emit light.

In one embodiment, the third compound may be a known fluorescent dopant.

For example, the third compound may be selected from the group consisting of Perylene, TBPe (2,5,8,11-tetra-tert-butylperylene), BCzVB (1,4-bis [2- (3-N-ethylcarbazoryl) (4,4'-bis [4-diphenylamino] styryl) biphenyl), DPAVB (4- (di bis (4-di-p-tolylamino) styryl] biphenyly), DSA-Ph (1-p-tolylamino) -4 ' (N, N'-dimethyl-quinacridone), DBQA (5,12-dibutylquinacridone), TTPA (N, N-diphenylamino) styryl-benzene), Coumarin 6, C545T, DMQA (9,10-bis [phenyl (m-tolyl) -amino] anthracene), BA-TTB (N ¹⁰ , ^{N 10, N 10 ', N} 10'-tetra-tolyl-9,9'-bianthracene-10,10'-diamine), BA-TAB (N 10, N 10, N 10 ', N 10' -tetraphenyl- 9,9'-bianthracene-10,10'-diamine) , BA-NPB (N 10, N 10 '-diphenyl-N 10, N 10'-dinaphthalenyl-9,9'-bianthracene-10,10'-diamine ), DEQ (N, N'-diethylquinacridone), DCM (4- (dicyanomethylene) -2-methyl- 6- [p- (dimethylamino) styryl] -4H- methyl-6- 4-pyran), DCJT (4- (dicyanomethylene) -2-methyl-6- (1,1,7,7-tetramethylgulolidyl-9- (1,1,7,7-tetramethyljulolidyl-9-enyl) -4H-pyran), DCJTI, DCJMTB, DPP (6,13-diphenylpentacene), DCDDC - (dicyanomethylene) -5,5-dimethyl-1 - [(4-dimethylamino) styryl] cyclohexene), AAAP (6-methyl- 3- [3- (1,1,6,6-tetramethyl- 2,4-dione), (PPA) (PSA), 2,3,5,6-tetrahydro-1H, 4H, 10H-11-oxa-3a-azabenzo [ (Np-styrylphenyl-Np-tolylamino) perylene, BSN (1,10-dicyano-substituted bis-styrylnaphthalene derivative) DBP (tetraphenyldibenzoperiflanthene), TBRb But are not limited to, 2,8-di-tert-butyl-5,11-bis (4-tert-butylphenyl) -6,12-diphenyltetracene or rubrene.

For example, the content of the third compound may be more than about 0 wt% to about 3 wt% based on the total weight of the light emitting layer, but is not limited thereto.

As another example, the content of the third compound may be at least about 0.01% by weight, at least about 0.1% by weight, at least about 0.3% by weight, at least about 0.5% by weight, at least about 0.9% by weight, But it is not limited thereto.

In one embodiment, the light emitting layer may further comprise a fourth compound. The fourth compound may act as a host, and the description of the fourth compound refers to the description of the first compound described above.

In one embodiment, the first compound and the fourth compound may or may not form an exciplex, but are not limited thereto.

In one embodiment, the first compound and the fourth compound are, independently from each other, a carbazole-containing compound, an aromatic amine compound, a? -Electron deficient complex aromatic compound, a phosphine oxide-containing compound and a sulfur oxide- ;

The first compound and the fourth compound may be different from each other, but are not limited thereto.

In another embodiment, the first compound is a hole transporting host and the fourth compound is an electron transporting host; or

The first compound may be an electron transporting host, and the fourth compound may be a hole transporting host, but is not limited thereto.

In yet another embodiment, i) the first compound is selected from a carbazole-containing compound and an aromatic amine compound, and the fourth compound is selected from the group consisting of a? -Electron deficient complex aromatic compound, a phosphine oxide- Containing compound; or

ii) the first compound is selected from a? -electron deficient complex aromatic compound, a phosphine oxide-containing compound and a sulfur oxide-containing compound, and the fourth compound is selected from a carbazole-containing compound and an aromatic amine compound However, the present invention is not limited thereto.

Specifically, the first compound is selected from among mCP, TCTA, CBP, mCBP, NPB, m-MTDATA and TPD, and the fourth compound is selected from B3PYMPM, B4PYMPM, TPBi, 3TPYMB, BmPyPB, TmPyPB, the compound BSFM, PO-T2T, PO15, DPEPO, and TSPO1, but is not limited thereto.

Specifically, the first compound is selected from B3PYMPM, B4PYMPM, TPBi, 3TPYMB, BmPyPB, TmPyPB, the compound BSFM, the compounds PO-T2T, PO15, DPEPO and TSPO1, mCBP, NPB, m-MTDATA and TPD, but is not limited thereto.

For example, the combination of the first compound and the fourth compound is selected from the group consisting of TCTA: B4PYMPM, TCTA: B3PYMPM, TCTA: TPBi, TCTA: 3TPYMB, TCTA: BmPyPB, TCTA: BSFM, CBP: B3PYMPM, mCP: B3PYMPM and NPB: BSFM, but is not limited thereto. When the combination of the first compound and the fourth compound is selected from those described above, the first compound and the fourth compound may form an exiplex.

When the light emitting layer further comprises the fourth compound, the weight ratio of the first compound and the fourth compound may be 20:80 to 80:20, but is not limited thereto. For example, the weight ratio of the first compound and the fourth compound may be 30:70 to 70:30, 40:60 to 60:40, or 50:50, but is not limited thereto.

A substrate (not shown) may further be provided on the lower portion of the first electrode 11 (the opposite side where the organic layer is located) or the upper portion of the second electrode 19 (the opposite side where the organic layer is located). As the substrate (not shown), a substrate used for a typical organic light emitting device can be used. A glass substrate or a transparent plastic substrate having excellent mechanical strength, thermal stability, transparency, surface smoothness, ease of handling and waterproofness can be used.

The first electrode 11 of the organic light emitting diode 10 may be an anode to which a positive voltage is applied and the second electrode 19 may be a cathode to which a negative voltage is applied . Conversely, the first electrode 11 may be a cathode and the second electrode 19 may be a cathode. For convenience, the first electrode 11 is an anode and the second electrode 19 is a cathode.

The first electrode 11 may be formed of a transparent electrode or a reflective electrode, and may be formed of a transparent electrode in the case of a bottom emission type. In the case of using a transparent electrode such as ITO, IZO, ZnO or graphene, it is possible to use Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, , And then forming a film of ITO, IZO, ZnO, or graphene thereon. The first electrode 11 may be formed by various known methods, for example, a vapor deposition method, a sputtering method, a spin coating method, or the like.

The organic layer 15 may further include a hole transporting region between the light emitting layer 16 and the first electrode 11 and may further include an electron transporting region between the light emitting layer 16 and the second electrode 19 . The hole transporting region is an area related to the injection and transport of holes from the anode to the light emitting layer, and the electron transporting region is an area related to the injection and transport of electrons from the cathode to the light emitting layer.

The hole transporting region may include at least one of a hole injecting layer, a hole transporting layer, an electron blocking layer, and a buffer layer.

The hole transporting region may include only a hole injecting layer, or may include only a hole transporting layer. Alternatively, the hole transporting region may have a structure of a hole injecting layer / a hole transporting layer or a hole injecting layer / a hole transporting layer / an electron blocking layer which are sequentially stacked from the first electrode 11.

When the hole transporting region includes a hole injecting layer, the hole injecting layer (HIL) may be formed on the first electrode 11 by various methods such as a vacuum deposition method, a spin coating method, a casting method, an LB method, have.

As the material used for the hole injection layer, a known hole injection material can be used. For example, a phthalocyanine compound such as copper phthalocyanine, m-MTDATA, TDATA, TAPC (4,4'-Cyclohexylidenebis [N, N-bis 2-naphthyl (phenyl) amino] triphenylamine, PANI / DBSA (polyaniline / dodecylbenzenesulfonic acid), PEDOT / PSS (Polyaniline / poly (4-styrenesulfonate)), PANI / CSA (polyaniline / camphorsulfonic acid) or PANI / PSS (1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile), and the like, but the present invention is not limited thereto.

When the hole transporting region includes a hole transporting layer, the hole transporting layer (HIL) is formed on the first electrode 11 or on the hole injecting layer by various methods such as vacuum deposition, spin coating, casting, LB .

A known hole transporting material may be used as the hole transporting layer. For example, mCP (1,3-bis (9-carbazolyl) benzene), TCTA (Tris (4- carbazoyl- , 4'-Bis (N-carbazolyl) -1,1'-biphenyl), mCBP (3,3-bis (carbazol-9- yl) bipheny), NPB (N, N'- N, N'-diphenyl- (1,1'-biphenyl) -4,4'-diamine), m-MTDATA (4,4 ' (N, N'-bis (3-methylphenyl) -N, N'-diphenylbenzidine).

The light emitting layer 16 may be formed on the hole transporting region by various methods such as a vacuum evaporation method, a spin coating method, a casting method, or an LB method.

In addition to the materials described above, the hole transporting region may further include a charge-generating material for improving conductivity. The charge-generating material may be uniformly or non-uniformly dispersed within the hole transport region.

The charge-producing material may be, for example, a p-dopant.

For example, the p-

Quinone derivatives such as TCNQ (tetracyanoquinodimethane) and F4-TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane);

Metal oxides such as rhenium oxide, tungsten oxide, and molybdenum oxide;

HAT-CN (1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile), and the like, but the present invention is not limited thereto.

The description of the light emitting layer 16 is given above.

An electron transporting region may be disposed above the light emitting layer 16, and the electron transporting region may include at least one of a hole blocking layer, an electron transporting layer, and an electron injection layer.

For example, the electron transporting region may have a structure of a hole blocking layer / electron transporting layer / electron injecting layer or electron transporting layer / electron injecting layer, but is not limited thereto. The electron transporting layer may have a single layer or a multi-layer structure including two or more different materials.

The forming conditions of the hole blocking layer, the electron transporting layer and the electron injecting layer in the electron transporting region refer to the forming conditions of the hole injecting layer.

For example, Alq ₃ , BCP (Bathocuproine), Bphen (4,7-diphenyl-1,10-phenanthroline), TAZ (3- (Biphenyl-4-yl) (4-tert-butylphenyl) -4-phenyl-4H-1,2,4-triazole), NTAZ (4- (naphthalen- 4-triazole), tBu-PBD (2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole), Balq (Bis (2-methyl-8-quinolinolato- O8) - (1,1'-Biphenyl- 4-olato) aluminum), Bebq 2 (Bis (10-hydroxybenzo [h] quinolinato) beryllium), AND (9,10-Di (naphth-2-yl) anthracene) , B3PYMPM (bis-4,6- (3,5-di-3-pyridylphenyl) -2-methylpyrimidine-dine), TPBi (2,2 ', 2''- (1,3,5-benzenetriyl) tris- [ 1-phenyl-1H-benzimidazole]), 3TPYMB (Tris (2,4,6-triMethyl-3- (pyridin- 3- yl) phenyl) borane), BmPyPB (1,3- pyridin-3-yl) phenyl benzene), TmPyPB (3,3 '- [5' - [3- (3-Pyridinyl) phenyl] [1,1 ': 3' -diyl] bispyridine), the following compound BSFM, the following compound PO-T2T, the following compound TSPO1, dibenzo [b, d] thiophene-2,8-diylbis lphosphine oxide), and the like, but the present invention is not limited thereto.

The electron transport layer may be doped with materials such as _{LiF, NaCl, CsF, Li 2} O, BaO, Liq, Rb 2 CO 3.

The electron injection layer can be formed using materials such as LiF, NaCl, CsF, Li ₂ O, BaO, Liq, Rb ₂ CO _3, and the like.

A second electrode 19 is formed on the organic layer 15. The second electrode 19 is made of an alkali metal such as lithium, sodium, potassium, rubidium or cesium, an alkaline earth metal such as beryllium, magnesium, calcium, strontium or barium, aluminum, scandium, vanadium, zinc, yttrium, indium, , Europium, terbium, ytterbium, alloys of two or more of them, or alloys of at least one of them with at least one of gold, silver, platinum, copper, manganese, titanium, cobalt, nickel, tungsten and tin , And a structure including at least two of them. If necessary, ultraviolet-ozone-treated ITO may be used. As the alloy, for example, ITO (indium tin oxide), IZO (indium zinc oxide), ZnO (zinc oxide), or graphene can be used. In the case of the top emission type, the second electrode 19 may be formed of a transparent oxide such as ITO, IZO, ZnO, or graphene.

The organic light emitting device has been described above with reference to FIG. 1, but the present invention is not limited thereto.

Hereinafter, an organic light emitting device according to one embodiment of the present invention will be described in more detail with reference to evaluation examples, reference examples, and examples. However, the present invention is not limited to the following Reference Examples and Examples.

[Example]

Evaluation Example 1: Calculation of HOMO energy level and LUMO energy level

Of B3PYMPM, TCTA, Ir (ppy) 2 (acac), Ir (mpp) 2 (acac), Ir (ppy) 2 (tmd), Ir (ppy) 3, Ir (mppy) 3 and Ir (chpy) ₃ HOMO Energy levels were obtained from DFT calculations for each compound. The results are shown in Table 1 and Fig.

compound HOMO energy level
(eV) LUMO energy level
(eV) B3PYMPM -6.8 -3.2 TCTA -5.8 -2.4 Ir (ppy) ₂ (acac) -5.5 -3.0 Ir (mpp) ₂ (acac) -5.1 -2.7 Ir (ppy) ₂ (tmd) -5.4 -2.9 Ir (ppy) ₃ -5.3 -2.8 Ir (mppy) ₃ -5.0 -2.2 Ir (chpy) ₃ -5.0 -2.5

Referring to Table 1 and _{2, Ir (ppy) 2 (acac} ), Ir (mpp) 2 (acac), Ir (ppy) 2 (tmd), Ir (ppy) 3, Ir (mppy) 3 and Ir (chpy) ₃ has a LUMO energy level higher than the LUMO energy level of B3PYMPM, respectively, and has a higher HOMO energy level than the HOMO energy level of TCTA. From this, Ir (ppy) ₂ (acac), Ir (mpp) ₂ (acac), Ir (ppy) ₂ (tmd). It is predicted that Ir (ppy) ₃ , Ir (mppy) ₃ and Ir (chpy) ₃ have hole trapping property.

Evaluation Example 2: Measurement of characteristics of trap assisted recombination

1) Reference Example 1

The glass substrate on which ITO was patterned to a thickness of 100 nm as an anode electrode was exposed to UV-ozone for 15 minutes and then washed with deionized water and isopropyl alcohol. TAPC was deposited on the glass substrate to form a 75 nm thick hole injection layer. TCTA was deposited on the hole injection layer to form a hole transport layer having a thickness of 1 nm. On the hole transport layer TCTA (first compound), B3PYMPM (Fourth compound), and Ir (ppy) ₃ (the second compound), the co-deposited (the first compound and the fourth compound is 1: 1 molar ratio, the second compound is 8 wt% of the weight of the light emitting layer) to form a light emitting layer with a thickness of 30 nm. B3PYMPM was deposited on the emission layer to form an electron transport layer having a thickness of 45 nm. LiF was deposited on the electron transport layer to form an electron injection layer with a thickness of 0.7 nm, followed by evaporation of Al to form a cathode having a thickness of 100 nm. Each layer was thermally deposited at a vacuum of 5 × 10 ^-7 Torr.

2) Reference Example 2

An organic light emitting device was fabricated in the same manner as in Reference Example 1, except that Ir (chpy) ₃ was used instead of Ir (ppy) _{3 in} forming the light emitting layer.

3) Reference Example 3

Except that the light emitting layer is formed when Ir (ppy) ₃ instead of Ir (mppy) ₃ was used to prepare a organic light emitting device in the same manner as in Reference Example 1.

4) Comparative Reference Example 1

An organic light emitting device was fabricated in the same manner as in Reference Example 1 except that Ir (ppy) ₂ (acac) was used instead of Ir (ppy) _{3 in} forming the light emitting layer.

5) Comparative Reference Example 2

An organic light emitting device was fabricated in the same manner as in Reference Example 1 except that Ir (ppy) ₂ (tmd) was used instead of Ir (ppy) _{3 in} forming the light emitting layer.

6) Comparative Reference Example 3

An organic light emitting device was fabricated in the same manner as in Reference Example 1, except that Ir (mpp) ₂ (acac) was used instead of Ir (ppy) _{3 in} forming the light emitting layer.

JVL characteristics were measured with a voltage-source-measurement unit (Keithley 237) and SpectraScan PR650 (Photo Research). Transient EL data was obtained by connecting a pulse generator (Agilent 8114A) and a spectrometer (SpectraPro-300i) to a photoelectric amplifier tube (Acton Research, PD-438). Mobility was obtained using a time-of-flight measuring device (Optel, TOF-401).

Driving voltage (JV), luminance-driving voltage (LV), luminance-driving voltage and luminance-external quantum efficiency were measured for Reference Examples 1 to 3 and Comparative Reference Examples 1 to 3, To 6, respectively.

3 and 4, the JV characteristics of Comparative Reference Examples 1 to 3 were found to be almost similar, and the current densities of Reference Examples 1 to 3 were found to be lower than the current densities of Comparative Reference Examples 1 to 3 there was. It was also found that the turn-on voltages of Reference Examples 1 to 3 were higher than the turn-on voltages of Comparative Reference Examples 1 to 3. The difference in J-V-L characteristics between Reference Examples 1 to 3 and Comparative Reference Examples 1 to 3 depends on the degree of trapping, because the charge trap of the dopant lowers J by decreasing the charge mobility in the light emitting layer.

Fig. 5 shows the luminance vs. driving voltage of the reference examples 1 to 3 and the comparative reference examples 1 to 3. Fig. From this, it can be seen that Reference Examples 1 to 3 are required to apply a higher driving voltage to achieve a specific luminance as compared with Comparative Reference Examples 1 to 3. This is believed to be due to the local electric field formed by the trap charge.

Fig. 6 shows the luminance vs. external quantum efficiency of Reference Examples 1 to 3 and Comparative Reference Examples 1 to 3. Fig. This maximum external quantum efficiency matches well with the theoretical maximum external quantum efficiency, indicating that the organic light emitting devices have good hole and electron balance.

Fig. 7 shows the transition EL of Reference Examples 1 to 3 and Comparative Reference Examples 1 to 3. Fig. Comparative Reference Examples 1 to 3 all showed no overshoot on the decay curve under reverse bias after the electric pulse was turned off. In contrast, Reference Examples 1 to 3 all exhibited an overshoot under reverse bias. This overshoot is due to recombination of the residual trapped charge in the dopant, which accelerates the process as the reverse bias increases. From JV characteristics and transient EL measurements, Langevin recombination is dominant in organic light emitting devices including heteroleptic dopants with relatively low dipole moments, and trap assisted recombination is dominant in organic light emitting devices including homoleptic dopants with relatively high dipole moments .

Evaluation Example 3: Langevin recombination vs. trap assisted recombination

The ratio of Langeubin recombination during total recombination was calculated using a drift-diffusion model. _{Ir (ppy) 2 (acac)} , Ir (mpp) 2 (acac), Ir (ppy) 2 (tmd), Ir (ppy) 3, Ir (mppy) 3 and Ir (chpy) with respect to _three based on the B3LYP density The dipole moments, trap radius, cross-sectional area and trap depth were calculated using the Gaussian09 program with molecular structure optimization by functional theory (DFT: B3LYP, structure optimization at 6-311G (d) / LANL2DZ level) Respectively.

Heteroleptic dopant Ir (ppy) ₂ (tmd) Ir (mpp) ₂ (acac) Ir (ppy) ₂ (acac) Dipole Moment (Debye) 1.4 1.64 1.83 Capture radius (nm) 0.21 0.26 0.28 Cross section (nm ² ) 0.18 0.21 0.24 Trap depth ( ΔE _t ) (eV) 0.4 0.7 0.3 Homoleptic dopant Ir (mppy) ₃ Ir (chpy) ₃ Ir (ppy) ₃ Dipole Moment (Debye) 5.38 6.18 6.36 Capture radius (nm) 0.47 0.51 0.51 Sectional area (nm ² ) 0.70 0.81 0.83 Trap depth (eV) 0.8 0.8 0.5

Figure 8 shows the ratio of rejuvenation of the total reassociation to trap radius or dipole moment and trap depth. Ratio of rangjubaeng recombination of calculated total recombining is Ir (ppy), respectively _{2 (tmd), Ir (ppy} ) 2 (acac) and Ir (mppy) ₂ was to about 0.74, 0.59 and 0.63 (acac), Ir (ppy) ₃ , Ir (mppy) ₃ and 0.21, 0.26, and 0.21, respectively, for Ir (chpy) ₃ .

From the theoretical calculations, it can be expected that the ratio of langeubin recombination to heteroleptic dopant is higher than homoreptic dopant, which is well correlated with experimental values.

10: Organic light emitting device
11: first electrode
15: Organic layer
16:
19: Second electrode

Claims (10)

A first electrode; A second electrode; And an organic layer interposed between the first electrode and the second electrode;
Wherein the organic layer comprises a light emitting layer;
Wherein the light emitting layer comprises a first compound, a second compound and a third compound;
Wherein the first compound, the second compound, and the third compound satisfy Formulas 1 to 3 below.
<Formula 1>
│H _HOMO - SD _HOMO │≥ 0.1 eV
<Formula 2>
μ _SD ≥ 3.2 ball
<Formula 3>
H _S1 > SD _S1 > FD _S1
Of the above formulas 1 to 3,
H _HOMO is the highest level occupied molecular orbital energy level of the first compound, SD _HOMO is the highest level occupied molecular orbital energy level of the second compound,
μ _SD is the dipole moment value of the second compound,
H _S1 is the lowest excited singlet energy level of the first compound, SD _S1 is the lowest excited singlet energy level of the second compound, and FD _S1 is the lowest excited singlet energy level of the first compound. The method according to claim 1,
Wherein the third compound further satisfies Formula 4:
<Formula 4>
μ _FD ≤ 2.0 debuggers
In the formula 4,
and μ _FD is the dipole moment value of the third compound. The method according to claim 1,
The first compound and the second compound satisfy the following formulas 1 and 2-1; Wherein the first compound and the second compound satisfy the following formulas 1-1 and 2, respectively.
<Formula 1>
│H _HOMO - SD _HOMO │≥ 0.1 eV
<Expression 1-1>
│H _HOMO - SD _HOMO │≥ 0.3 eV
<Formula 2>
μ _SD ≥ 3.2 ball
<Formula 2-1>
μ _SD ≥ 6.0 ball
Of the above-mentioned formulas 1, 1-1, 2 and 2-1,
H _HOMO is the highest level occupied molecular orbital energy level of the first compound, SD _HOMO is the highest level occupied molecular orbital energy level of the second compound,
and μ _SD is the dipole moment value of the second compound. The method according to claim 1,
Wherein the molar concentration of the first compound is greater than or equal to the molarity of the second compound and the molarity of the third compound. The method according to claim 1,
Wherein the molar concentration of the second compound is greater than or equal to the molar concentration of the third compound. The method according to claim 1,
And the second compound comprises a metal atom having an atomic weight of 40 or more. The method according to claim 1,
Wherein the second compound is a homoleptic organometallic compound. The method according to claim 1,
And the third compound emits light. The method according to claim 1,
Wherein the light emitting layer further comprises a fourth compound. 10. The method of claim 9,
Wherein the first compound and the fourth compound form an exciplex.

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