Organic electroluminescent device

Abstract

The present invention relates to an organic electroluminescent device comprising a hole-injection layer comprising a metal complex as a main component and a method for producing the organic electroluminescent device.

Claims

1. An organic electroluminescent device comprising: a cathode; an anode; at least one emitting layer arranged between the cathode and the anode; at least one hole-transport layer arranged between the anode and the at least one emitting layer; and at least one hole-injection layer arranged between the anode and the at least one hole-transport layer, where the at least one hole-injection layer comprises at least 90% by weight, based on the total weight of the hole-injection layer, of at least one bismuth or gallium complex, and where the reduction potential of the bismuth or gallium complex is higher than or equal to −3.5 V and lower than or equal to 0.5 V vs. Fc/Fc.sup.+, determined by cyclic voltammetry.

2. The organic electroluminescent device according to claim 1, wherein the reduction potential of the bismuth or gallium complex is higher than or equal to −3.0 V and lower than or equal to 0 V vs. Fc/Fc.sup.+.

3. The organic electroluminescent device according to claim 1, wherein the hole-injection layer has a thickness of from 0.5 to 50 nm.

4. The organic electroluminescent device according to claim 1, wherein the hole-injection layer has a thickness of from 1 to 5 nm.

5. The organic electroluminescent device according to claim 1, wherein the hole-injection layer is adjacent to the anode on the anode side and adjacent to the hole-transport layer on the cathode side.

6. The organic electroluminescent device according to claim 1, wherein the metal complex is a bismuth complex comprising a ligand of the following structure: ##STR00098## where R.sup.11 and R.sup.12 are selected, identically or differently, from the group consisting of O, S, Se, NH and NR.sup.14, where R.sup.14 is an alkyl or aryl group; where R.sup.14 and R.sup.13 may form a ring with one other; and R.sup.13 is selected from the group consisting of a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms, an alkenyl or alkinyl group having 2 to 40 C atoms, a branched or cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R, where in each case one or more non-adjacent CH.sub.2 groups may be replaced by RC═CR, C≡C, Si(R).sub.2, C═O, C═S, C═NR, P(═O)(R), SO, SO.sub.2, NR, O, S or CONR and where one or more H atoms may be replaced by D, F, Cl, Br, I or CN, an aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R, an aryloxy or heteroaryloxy group having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R, an aralkyl or heteroaralkyl group having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R, and a diarylamino group, diheteroarylamino group or arylheteroarylamino group having 10 to 40 aromatic ring atoms, which may be substituted by one or more radicals R; where R.sup.13 may form a ring with at least one of the radical R.sup.12; and R is on each occurrence, identically or differently, H, D, For, a straight-chain alkyl group having 1 to 20 C atoms or a branched or cyclic alkyl group having 3 to 20 C atoms, where one or more H atoms in the straight-chain, branched or cyclic alkyl groups may be replaced by F, an aromatic or heteroaromatic ring system having 5 to 20 aromatic ring atoms, in which one or more H atoms in the aromatic or heteroaromatic ring system may be replaced by F; where two or more substituents R may also form a mono- or polycyclic, aliphatic or aromatic ring system with one another.

7. The organic electroluminescent device according to claim 1, wherein the bismuth complex is selected from bismuth (III) acetates and bismuth (III) benzoates.

8. The organic electroluminescent device according to claim 1, wherein the bismuth complex corresponds to a complex of the Formula (P-1): ##STR00099## where R is on each occurrence, identically or differently, H, D, F or, a straight-chain alkyl group having 1 to 20 C atoms or a branched or cyclic alkyl group having 3 to 20 C atoms, where one or more H atoms in the straight-chain, branched or cyclic alkyl groups may be replaced by F, an aromatic or heteroaromatic ring system having 5 to 20 aromatic ring atoms, in which one or more H atoms in the aromatic or heteroaromatic ring system may be replaced by F; where two or more substituents R may also form a mono- or polycyclic, aliphatic or aromatic ring system with one another.

9. The organic electroluminescent device according to claim 1, wherein the at least one hole-transport layer comprises at least one triarylamine.

10. The organic electroluminescent device according to claim 1, wherein the at least one hole-transport layer comprises at least one triarylamine, which corresponds to a compound of Formula (1) or to a polymer comprising at least one structural unit of the Formula (2): ##STR00100## where A.sup.1 is on each occurrence, identically or differently, a mono- or polycyclic, aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R.sup.1; R.sup.1 is on each occurrence, identically or differently, H, D, F, Cl, Br, I, N(R.sup.2).sub.2, CN, NO.sub.2, Si(R.sup.2).sub.3, B(OR.sup.2).sub.2, C(═O)R.sup.2, P(═O)(R.sup.2).sub.2, S(═O)R.sup.2, S(═O).sub.2R.sup.2, OSO.sub.2R.sup.2, a straight-chain alkyl, alkoxy or thioalkoxy group having 1 to 40 C atoms or a branched or cyclic alkyl, alkoxy or thioalkoxy group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R.sup.2, where one or more non-adjacent CH.sub.2 groups may be replaced by R.sup.2C═CR.sup.2, C≡C, Si(R.sup.2).sub.2, C═O, C═S, C═NR.sup.2, P(═O)(R.sup.2), SO, SO.sub.2, NR.sup.2, O, S or CONR.sup.2 and where one or more H atoms may be replaced by D, F, Cl, Br, I or CN, or a mono- or polycyclic, aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R.sup.2, or an aryloxy or heteroaryloxy group having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R.sup.2, or an aralkyl or heteroaralkyl group having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R.sup.2, or a diarylamino group, diheteroarylamino group or arylheteroarylamino group having 10 to 40 aromatic ring atoms, which may be substituted by one or more radicals R.sup.2, where two or more radicals R.sup.1 here may also form a mono- or polycyclic, aliphatic or aromatic ring system with one another; R.sup.2 is on each occurrence, identically or differently, H, D, F or an aliphatic hydrocarbon radical having 1 to 20 C atoms, an aromatic and/or a heteroaromatic hydrocarbon radical having 5 to 20 C atoms, in which, in addition, one or more H atoms may be replaced by F; where two or more substituents R.sup.2 may also form a mono- or polycyclic, aliphatic or aromatic ring system with one another; and the dashed lines in Formula (2) represent bonds to adjacent structural limits in the polymer.

11. The organic electroluminescent device according to claim 1, wherein the at least one hole-transport layer comprises at least one monotriarylamine, which corresponds to a compound of one of the Formulae (T-1) to (T-7), ##STR00101## ##STR00102## wherein Ar.sup.1 is on each occurrence, identically or differently, a mono- or polycyclic, aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R.sup.1; Z is on each occurrence, identically or differently, N or CR.sup.1, where Z is equal to C if a substituent is bonded; X and Y are on each occurrence, identically or differently, a single bond, O, S, Se, BR.sup.1, C(R.sup.1).sub.2, Si(R.sup.1).sub.2, NR.sup.1, PR.sup.1, C(R.sup.1).sub.2—C(R.sup.1).sub.2 or CR.sup.1═CR.sup.1; E is O, S, Se, BR.sup.1, C(R.sup.1).sub.2, Si(R.sup.1).sub.2, NR.sup.1, PR.sup.1, C(R.sup.1).sub.2—C(R.sup.1).sub.2 or CR.sup.1═CR.sup.1; R.sup.1 is on each occurrence, identically or differently, H, D, F, Cl, Br, I, N(R.sup.2).sub.2, CN, NO.sub.2, Si(R.sup.2).sub.3, B(OR.sup.2).sub.2, C(═O)R.sup.2, P(═O)(R.sup.2).sub.2, S(═O)R.sup.2, S(═O).sub.2R.sup.2, OSO.sub.2R.sup.2, a straight-chain alkyl, alkoxy or thioalkoxy group having 1 to 40 C atoms or a branched or cyclic alkyl, alkoxy or thioalkoxy group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R.sup.2, where one or more non-adjacent CH.sub.2 groups may be replaced by R.sup.2C═CR.sup.2, C≡C, Si(R.sup.2).sub.2, C═O, C═S, C═NR.sup.2, P(═O)(R.sup.2), SO, SO.sub.2, NR.sup.2, O, S or CONR.sup.2 and where one or more H atoms may be replaced by D, F, Cl, Br, I or CN, or a mono- or polycyclic, aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R.sup.2, or an aryloxy or heteroaryloxy group having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R.sup.2, or an aralkyl or heteroaralkyl group having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R.sup.2, or a diarylamino group, dihtteroarylamino group or arylheteroarylamino group having 10 to 40 aromatic ring atoms, which may be substituted by one or more radicals R.sup.2, where two or more radicals R.sup.1 here may also form a mono- or polycyclic, aliphatic or aromatic ring system with one another; R.sup.2 is on each occurrence, identically or differently, H, D, F or an aliphatic hydrocarbon radical having 1 to 20 C atoms, an aromatic and/or a heteroaromatic hydrocarbon radical having 5 to 20 C atoms, in which, in addition, one or more H atoms may be replaced by F; where two or more substituents R.sup.2 may also form a mono- or polycyclic, aliphatic or aromatic ring system with one another; i is on each occurrence, identically or differently, 0 or 1, where the sum of all i is at least equal to 1; p is equal to 0 or 1; m and n are, identically or differently, 0 or 1, where the sum of m and n is equal to 1 or 2.

12. The organic electroluminescent device according to claim 1, wherein the at least one hole-transport layer comprises at least one monotriarylamine, which corresponds to a compound of one of the Formulae (T-2-1) to (T-2-4), ##STR00103## wherein Ar.sup.1 is on each occurrence, identically or differently, a mono- or polycyclic, aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R.sup.1; Z is on each occurrence, identically or differently, N or CR.sup.1, where Z is equal to C if a substituent is bonded; X is on each occurrence, identically or differently, a single bond, O, S, Se, BR.sup.1, C(R.sup.1).sub.2, Si(R.sup.1).sub.2, NR.sup.1, PR.sup.1, C(R.sup.1).sub.2—C(R.sup.1).sub.2 or CR.sup.1═CR.sup.1; R.sup.1 is on each occurrence, identically or differently, H, D, F, Cl, Br, I, N(R.sup.2).sub.2, CN, NO.sub.2, Si(R.sup.2).sub.3, B(OR.sup.2).sub.2, C(═O)R.sup.2, P(═O)(R.sup.2).sub.2, S(═O)R.sup.2, S(═O).sub.2R.sup.2, OSO.sub.2R.sup.2, a straight-chain alkyl, alkoxy or thioalkoxy group having 1 to 40 C atoms or a branched or cyclic alkyl, alkoxy or thioalkoxy group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R.sup.2, where one or more non-adjacent CH2 groups may be replaced by R.sup.2C═CR.sup.2, C≡C, Si(R.sup.2).sub.2, C═O, C═S, C═NR.sup.2, P(═O)(R.sup.2), SO, SO.sub.2, NR.sup.2, O, S or CONR.sup.2 and where one or more H atoms may be replaced by D, F, Cl, Br, I or CN, or a mono- or polycyclic, aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R.sup.2, or an aryloxy or heteroaryloxy group having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R.sup.2, or an aralkyl or heteroaralkyl group having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R.sup.2, or a diarylamino group, diheteroarylamino group or arylheteroarylamino group having 10 to 40 aromatic ring atoms, which may be substituted by one or more radicals R.sup.2, where two or more radicals R.sup.1 here may also form a mono- or polycyclic, aliphatic or aromatic ring system with one another; R.sup.2 is on each occurrence, identically or differently, H, D, F or an aliphatic hydrocarbon radical having 1 to 20 C atoms, an aromatic and/or a heteroaromatic hydrocarbon radical having 5 to 20 C atoms, in which, in addition, one or more H atoms may be replaced by F; where two or more substituents R.sup.2 may also form a mono- or polycyclic, aliphatic or aromatic ring system with one another; and p is equal to 0 or 1.

13. The organic electroluminescent device according to claim 12, wherein the at least one monotriarylamine corresponds to a compound of formula (T-2-1).

14. The organic electroluminescent device according to claim 11, wherein X is a single bond and Z is C(R.sup.1).sub.2.

15. A method for producing the organic electroluminescent device according to claim 1 comprising the following steps: a. Depositing a hole-injection layer comprising at least 90% by weight, based on the total weight of the hole-injection layer, of at least one bismuth complex or gallium complex on an anode; b. Depositing at least one hole-transport layer on the hole-injection layer; c. Depositing at least one emitting layer; d. Forming a cathode.

16. A method according to claim 15, wherein the hole-injection layer, the hole-transport layer and the emitting layer are deposited, differently or identically, via a vapour deposition process and/or a solution-based process.

17. The organic electroluminescent device according to claim 1, wherein the bismuth or gallium complexes are selected from the group consisting of ##STR00104## ##STR00105##

Description

EXAMPLES

Example 1: Hole Only Devices

(1) The data for various hole only devices are presented in the non-limiting examples below (see Tables 1 to 2). The substrates used are glass plates coated with structured ITO (indium tin oxide) in a thickness of 50 nm.

(2) Freshly cleaned substrates are transferred into the evaporation tool. Here the substrates are preconditioned with oxygen plasma for 130 s and afterwards treated with argon plasma for 150 s.

(3) Afterwards several organic layers are deposited by physical vapour deposition.

(4) The thickness of the layers is determined by reference experiments, where thick layers of roughly 100 nm organic material are deposited. The thickness is measured during the evaporation by a thin-film thickness monitor, based on quartz crystal microbalance, f.e. Inficon. The organic layer is protected by evaporation of a thin aluminium film on top. Then, the real thickness of the organic layer is measured by a surface profiler, f.e. K-LA-Tencor P7. The tooling factor of the thin-film monitor is adapted that the film thickness of the surface profiler and the thin film monitor is the same. The devices basically have the following layer structure: substrate/hole-injection layer (HIL)/hole-transport layer (HTL) and finally a cathode. The cathode is formed by an aluminium layer with a thickness of 100 nm. The precise structure of the devices is shown in table 1. The materials required for the production of the devices are shown in table 3.

(5) All materials are applied by thermal vapour deposition in a vacuum chamber. An expression such as HTM1:HIM1(5%) here means that material HTM1 is present in the layer in a proportion by volume of 95% and HIM1 is present in the layer in a proportion of 5%. Analogously, other layers may also consist of a mixture of two or more materials.

(6) The devices are characterised by current/voltage measurement. The data for the various devices containing inventive and comparative materials are summarised in table 2 (U@10 mA/cm.sup.2 means the voltage of the device at a current density of 10 mA/cm.sup.2 and U@100 mA/cm.sup.2 means the voltage of the device at a current density of 100 mA/cm.sup.2).

(7) TABLE-US-00001 TABLE 1 HIL HTL cathode Ex. Thickness/nm Thickness/nm Thickness/nm V1 HATCN HTM1 Al 3 nm 100 nm 100 nm V2 HATCN HTM2 Al 3 nm 100 nm 100 nm V3 HTM1:HIM1(5%) HTM1 Al 10 nm  100 nm 100 nm V4 — HTM1 Al 100 nm 100 nm E1 HIM1 HTM1 Al 1.5 nm   100 nm 100 nm E2 HIM1 HTM1 Al 2 nm 100 nm 100 nm E3 HIM1 HTM1 Al 2.5 nm   100 nm 100 nm E4 HIM1 HTM1 Al 3 nm 100 nm 100 nm E5 HIM1 HTM2 Al 3 nm 100 nm 100 nm E6 HIM1 HTM3 Al 3 nm 100 nm 100 nm E7 HIM1 HTM4 Al 3 nm 100 nm 100 nm E8 HIM1 HTM5 Al 2 nm 100 nm 100 nm E9 HIM1 HTM5 Al 4 nm 100 nm 100 nm

(8) TABLE-US-00002 TABLE 2 U @ 10 mA/cm.sup.2 U @ 100 mA/cm.sup.2 Ex. [V] [V] V1 1.5 2.3 V2 1.9 3.7 V3 1.5 2.2 V4 2.9 4.6 E1 1.5 2.2 E2 1.5 2.1 E3 1.5 2.1 E4 1.5 2.2 E5 1.8 2.9 E6 1.6 2.7 E7 1.7 3.0 E8 1.8 2.7 E9 1.9 3.3

(9) TABLE-US-00003 TABLE 3 Structures of the materials used 0 HIM1**, reduction potential: −2.24 V vs. Fc/Fc.sup.+ as determined by the cyclic voltammetry measurement described above. *Synthesis according to WO 2012/035267, WO 2013/120577 **Synthesis according to WO 2013/182389

(10) Devices with the structures shown in table 1 are produced. Table 2 shows the performance data of the examples described. The devices are hole only devices comprising a hole-injection layer according to the invention or according to the prior art. It can be shown, that very low voltages can be obtained with thin hole-injection layers consisting of HIM1 (E1 to E9) in comparison with devices, which do not comprise any hole-injection layer (V4). Furthermore, it can be shown that hole-injection layers consisting of HIM1 lead to a decrease in the operating voltage, which is comparable (V1 vs. E4) or even better (V2 vs. E5) than the operating voltage obtained when a hole-injection layer consisting of HATCN is used. Finally, the operating voltage obtained with a hole-injection layer consisting of HIM1 is comparable with the operating voltage obtained with a p-doped layer (V3 in comparison with E1-E4), whereas only one evaporation source is needed for the manufacture of the devices corresponding to E1-E4 instead of two evaporation sources for the manufacture of the device corresponding to V3.

Example 2: OLEDs

(11) The data for various OLEDs are presented below (see Tables 4 to 5). The substrates used are glass plates coated with structured ITO (indium tin oxide) in a thickness of 50 nm. The OLEDs basically have the following layer structure: substrate/hole-injection layer (HIL)/hole-transport layer (HTL)/electron-blocking layer (EBL)/emission layer (EML)/hole-blocking layer/electron-transport layer (ETL)/electron-injection layer (EIL) and finally a cathode. The cathode is formed by an aluminium layer with a thickness of 100 nm. The precise structure of the OLEDs is shown in table 4. The materials required for the production of the OLEDs are shown in table 6.

(12) All materials are applied by thermal vapour deposition in a vacuum chamber. The emission layer here always consists of at least one matrix material (host material) and an emitting dopant (emitter), which is admixed with the matrix material or matrix materials in a certain proportion by volume by co-evaporation. An expression such as SMB:SEB (5%) here means that material SMB is present in the layer in a proportion by volume of 95% SEB is present in the layer in a proportion of 5%. Analogously, other layers may also consist of a mixture of two or more materials.

(13) The OLEDs are characterised by standard methods. For this purpose, the electroluminescence spectra and the external quantum efficiency (EQE, measured in percent) as a function of the luminous density, calculated from current/voltage/luminous density characteristic lines (IUL characteristic lines) assuming Lambert emission characteristics. The expression EQE @ 10 mA/cm.sup.2 denotes the external quantum efficiency at an operating current density of 10 mA/cm.sup.2.

(14) The lifetime LT80 is the time until the brightness drops to 80% of the initial brightness (f.e. from initial brightness of 6000 cd/m.sup.2 to 4800 cd/m.sup.2) at a constant current density of 60 mA/cm2. The data for the various OLEDs containing inventive and comparative materials are summarised in table 5.

(15) TABLE-US-00004 TABLE 4 Device Setup HIL HTL EBL EML ETL EIL Ex. Thickness/nm Thickness/nm Thickness/nm Thickness/nm Thickness/nm Thickness/nm V1 HAT-CN(3) HTM2 185 nm HTM2 10 nm SMB:SEB(5%) 20 nm ETM:LiQ(50%) 30 nm LiQ 1 nm V2 HAT-CN(5) HTM2 185 nm HTM2 10 nm SMB:SEB(5%) 20 nm ETM:LiQ(50%) 30 nm LiQ 1 nm E1 HIM2(3) HTM2 185 nm HTM2 10 nm SMB:SEB(5%) 20 nm ETM:LiQ(50%) 30 nm LiQ 1 nm E1 HIM2(3) HTM1 185 nm HTM2 10 nm SMB:SEB(5%) 20 nm ETM:LiQ(50%) 30 nm LiQ 1 nm

(16) TABLE-US-00005 TABLE 5 Data for the OLEDs U EQE LT80 @ 10 mA/cm.sup.2 @ 10 mA/cm.sup.2 @ 60 mA/cm.sup.2 [V] [%] [h] V1 5.8 6.6 90 V2 5.5 5.9 131 E1 4.3 6.8 435 E2 4.0 7.9 311

(17) TABLE-US-00006 TABLE 6 Structures of the materials used

(18) Table 5 shows the performance data of the examples described above. Especially for example E1 much lower voltage, better efficiency and much better lifetime is achieved in a blue fluorescent device in comparison to example V1 and V2.