Fluorescent organic light emitting elements having high efficiency

Abstract

The present invention relates to organic light emitting elements, comprising thermally activated delayed fluorescence (TADF) emitters and/or hosts of formula ##STR00001##
which have a sufficiently small energy gap between S.sub.1 and T.sub.1 (ΔE.sub.ST) to enable up-conversion of the triplet exciton from T.sub.1 to S.sub.1. The organic light emitting elements show high electroluminescent efficiency.

Claims

1. A compound of formula I ##STR00088## wherein X is independently in each occurrence O, S or NR.sup.9, Y.sup.1, Y.sup.2, Y.sup.3 and Y.sup.4 are independently of each other a direct bond, or a group of formula —[A.sup.1]—[A.sup.2].sub.y—, wherein A.sup.1 and A.sup.2 are independently of each other —CH═CH—, —C≡C— or a C.sub.6-C.sub.10arylene group, which may optionally be substituted by one or more C.sub.1-C.sub.25alkyl groups; y is 0, or 1; R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are independently of each other H, D, F, Cl, a C.sub.1-C.sub.25alkyl group, a C.sub.1-C.sub.25alkoxy group, a C.sub.6-C.sub.10aryloxy group, or a donor group of formula ##STR00089## X.sup.1 is O, S, N(R.sup.15), C(═O), C(R.sup.16)(R.sup.17), B(R.sup.18), or Si(R.sup.19)(R.sup.20), R.sup.9 is H, a C.sub.1-C.sub.25alkyl group, or a C.sub.6-C.sub.10aryl group; R.sup.10, R.sup.11, R.sup.21 and R.sup.21′ are independently of each other H, D, F, Cl, or a C.sub.1-C.sub.25alkyl group; R.sup.15, R.sup.16, R.sup.17, R.sup.18, R.sup.19 and R.sup.20 are independently of each other H, D, a C.sub.1-C.sub.25alkyl group, or a C.sub.6-C.sub.14aryl group, which can optionally be substituted by one, or more groups selected from a C.sub.1-C.sub.25alkyl group, a C.sub.1-C.sub.25alkoxy group and a C.sub.6-C.sub.10aryloxy group; with the proviso that at least one donor group of formula (Xa), or (Xd) is present in the compound of formula (I).

2. The compound according to claim 1, which wherein the compound is a compound of any of formula (Ia) to (If) ##STR00090## ##STR00091## wherein Y.sup.1, Y.sup.2, Y.sup.3, Y.sup.4, R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are as defined in claim 1.

3. The compound according to claim 1, wherein Y.sup.1, Y.sup.2, Y.sup.3 and Y.sup.4 are independently of each other a direct bond, or a group of formula ##STR00092##

4. The compound according to claim 1, wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are independently of each other H, a C.sub.1-C.sub.25alkyl group, a C.sub.1-C.sub.25alkoxy group, a C.sub.6-C.sub.10aryloxy group, a donor group of formula ##STR00093## X.sup.1 is O, S, C(O), N(R.sup.15), or C(R.sup.16)(R.sup.17); and R.sup.10, R.sup.11, R.sup.21 and R.sup.21′ are independently of each other H, or a C.sub.1-C.sub.25alkyl group; R.sup.15 is a group of formula ##STR00094## R.sup.16 and R.sup.17 are independently of each other H, a C.sub.1-C.sub.25alkyl group; R.sup.22 and R.sup.23 are independently of each other H, a C.sub.1-C.sub.25alkyl group, a C.sub.1-C.sub.25alkoxy group, or a C.sub.6-C.sub.10aryloxy group; with the proviso that at least one of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 is a donor group of formula (Xa), or (Xd).

5. The compound according to claim 4, wherein the donor group is a donor group of formula (Xa), wherein X.sup.1 is O, S, C(CH.sub.3)(CH.sub.3), C(═O), ##STR00095## or a donor group of formula (Xd), wherein R.sup.21 and R.sup.21′ are H.

6. The compound according to claim 1, wherein the donor group is a group of formula ##STR00096## ##STR00097##

7. The organic light-emitting element according to claim 1, wherein the compound of formula (I) is a compound of formula (Ia), (Ib), (Ic), (Id), (Ie), or (If), wherein Y.sup.1 and Y.sup.3 are a direct bond; R.sup.1 and R.sup.3 are H; Y.sup.2 and Y.sup.4 are a direct bond, or a group of formula ##STR00098## R.sup.2 and R.sup.4 are independently of each other a donor group of formula (Xa), or (Xd); or a compound of formula (Ia), (Ib), (Ic), (Id), (Ie), or (If), wherein Y.sup.2 and Y.sup.4 are a direct bond; R.sup.2 and R.sup.4 are H; Y.sup.1 and Y.sup.3 are a direct bond, or a group of formula ##STR00099## R.sup.1 and R.sup.3 are independently of each other a donor group of formula (Xa), or (Xd); or a compound of formula (Ia), (Ib), (Ic), (Id), (Ie), or (If), wherein Y.sup.4 is a direct bond, or a group of formula ##STR00100## R.sup.4 is a donor group of formula (Xa), or (Xd); Y.sup.2 is a group of formula ##STR00101## R.sup.2 is H; Y.sup.1 and Y.sup.3 are a direct bond; R.sup.1 and R.sup.3 are H; or a compound of formula (Ia), (Ib), (Ic), (Id), (Ie), or (If), wherein Y.sup.1 is a direct bond, or a group of formula ##STR00102## R.sup.1 is a donor group of formula (Xa), or (Xd); Y.sup.2, Y.sup.3 and Y.sup.4 are a group of formula ##STR00103## R.sup.2, R.sup.3 and R.sup.4 are H, wherein the donor group (Xa) is a group of formula ##STR00104## ##STR00105## and the donor group (Xd) is a group of formula ##STR00106##

8. A light-emitting layer comprising the compound according to claim 1.

9. An organic light emitting element, comprising the compound of formula (I) according to claim 1.

10. The organic light-emitting element according to claim 9, comprising a light-emitting layer, wherein the light-emitting layer comprises a host material and a guest material, wherein the guest material comprises the compound of formula (I).

11. The organic light-emitting element according to claim 9, comprising a light-emitting layer, wherein the light-emitting layer comprises a host material and a guest material, wherein the host material comprises the compound of formula (I).

12. The organic light-emitting element according to claim 9 wherein the organic light-emitting element emits delayed fluorescence.

13. A device selected from the group consisting of a electrophotographic photoreceptor, photoelectric converter, sensor, dye laser, solar cell device and organic light emitting element, wherein the device comprises a compound according to claim 1.

14. The compound according to claim 1, wherein the compound exhibits delayed fluorescence emission.

15. The compound according to claim 1, wherein R.sup.l, R.sup.2, R.sup.3 and R.sup.4 are independently of each other H, D, F, Cl, a C1-C25alkyl group, a C1-C25alkoxy group, a C6-C.sub.10aryloxy group, or a donor group of formula ##STR00107## X.sup.1 is C(R.sup.16)(R.sup.17), R.sup.10 and R.sup.11 are independently of each other H, D, F, Cl, or a C.sub.1-C.sub.25alkyl group; and R.sup.16 and R.sup.17 are independently of each other H, D, a C.sub.1-C.sub.25alkyl group, or a C.sub.6-C.sub.14aryl group, which can optionally be substituted by one, or more groups selected from a C.sub.1-C.sub.25alkyl group, a C.sub.1-C.sub.25alkoxy group and a C.sub.6-C.sub.10aryloxy group.

16. The compound according to claim 1, wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are independently of each other H, D, F, Cl, a C.sub.1-C.sub.25alkyl group, a C.sub.1-C.sub.25alkoxy group, a C.sub.6-C.sub.10aryloxy group, or a donor group of formula ##STR00108## X.sup.1 is O, S, N(R.sup.15), C(=O), C(R.sup.16)(R.sup.17), B(R.sup.18), or Si(R.sup.19)(R.sup.20), R.sup.9 is H, a C.sub.1-C.sub.25alkyl group, or a C.sub.6-C.sub.10aryl group; R.sup.10 and R.sup.11 are independently of each other H, D, F, Cl, or a C.sub.1-C.sub.25alkyl group; and R.sup.15, R.sup.16, R.sup.17, R.sup.18, R.sup.19, and R.sup.20 are independently of each other H, D, a C.sub.1-C.sub.25alkyl group, or a C.sub.6-C.sub.14aryl group, which can optionally be substituted by one, or more groups selected from a C.sub.1-C.sub.25alkyl group, a C.sub.1-C.sub.25alkoxy group and a C.sub.6-C.sub.10aryloxy group.

17. The compound according to claim 1, wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are independently of each other H, D, F, Cl, a C.sub.1-C.sub.25alkyl group, a C.sub.1-C.sub.25alkoxy group, a C.sub.6-C.sub.10aryloxy group, or a donor group of formula ##STR00109## X.sup.1 is O, S, N(R.sup.15), C(=O), C(R.sup.16)(R.sup.17), B(R.sup.18), or Si(R.sup.19)(R.sup.20), R.sup.9 is H, a C.sub.1-C.sub.25alkyl group, or a C.sub.6-C.sub.10aryl group; R.sup.21 and R.sup.21′ are independently of each other H, D, F, Cl, or a C.sub.1-C.sub.25alkyl group; and R.sup.15, R.sup.16, R.sup.17, R.sup.18, R.sup.19 and R.sup.20 are independently of each other H, D, a C.sub.1-C.sub.25alkyl group, or a C.sub.6-C.sub.14aryl group, which can optionally be substituted by one, or more groups selected from a C.sub.1-C.sub.25alkyl group, a C.sub.1-C.sub.25alkoxy group and a C.sub.6-C.sub.10aryloxy group.

Description

EXAMPLES

Example 1

(1) ##STR00082##

(2) a) 1,4-Diaminohydroquinone-HCl (14.08 mol) and poly-phosphoric acid (60 g) are placed in a 300 ml flask. While stirring, 4-bromobenzoic acid (28.16 mol) is added. The mixture is heated at 150° C. overnight (20 hours). After cooling to room temperature, the mixture is poured into H.sub.2O and generated solid is filtered and washed with Saturated NaHCO.sub.3 aq, H.sub.2O and EtOH. Dark grey solid is obtained by drying in vacuum (yield: 84.4%).

(3) ##STR00083##

(4) b) The product from example 1a (0.62 mmol), phenoxazine (1.27 mmol), palladium acetate (0.01 mmol), tri-tert-buthylphosphine (0.03 mmol), sodium t-buthoxide (1.85 mmol) and 14 ml of toluene are placed in a 50 ml flask. The mixture is stirred at 110° C. overnight and cooled. The mixture is filtered and the solid is washed with toluene, EtOH, H.sub.2O and MeOH. Yellow solid is obtained by drying in vacuum (yield: 37.4%). The product is subsequently purified using zone sublimation. .sup.1H-NMR (ppm, CDCl3): 8.52 (d, 4H), 8.00 (s, 2H), 7.57 (d, 4H), 6.78-6.60 (m, 12H), 6.02 (d, 4H)

Example 2

(5) ##STR00084##

(6) The product from example 1a (1.06 mmol), phenothiazine (2.18 mmol), palladium acetate (0.02 mmol), tri-tert-buthylphosphine (0.04 mmol), sodium t-buthoxide (3.19 mmol) and 24 ml of toluene are placed in a 50 ml flask. The mixture is stirred at 110° C. overnight and cooled. The mixture is filtered and the solid is washed with toluene:hexane=1:1, EtOH, H.sub.2O and MeOH. Yellow solid is obtained by drying in vacuum (yield: 37.4%). The product is subsequently purified using zone sublimation. .sup.1H-NMR (ppm, CDCl3): 8.31 (d, 4H), 7.91 (s, 2H), 7.38 (d, 4H), 7.13 (t, 4H), 7.04 (t, 4H), 7.04 (t, 4H), 6.86 (d, 4H)

Example 3

(7) ##STR00085##

(8) The product from example 1a (2.13 mmol), 9,9-dimethyl-10H-acridine (4.36 mmol), palladium acetate (0.04 mmol), tri-tert-buthylphosphine (0.09 mmol), sodium t-buthoxide (6.38 mmol) and 12 ml of toluene are placed in a 50 ml flask. The mixture is stirred at 110° C. overnight and cooled. The mixture is poured into H.sub.2O, yielding precipitation. The solid is filtered and washed with H.sub.2O, followed by EtOH. The crude product is purified by flash chromatography on silica gel with CH.sub.2Cl.sub.2 and hexane (1:3) as eluent, yielding yellowish solid (yield: 57.5%). The product is subsequently purified using zone sublimation. .sup.1H-NMR (ppm, CDCl3): 8.56 (d, 4H), 8.03 (s, 2H), 7.57 (d, 4H), 7.49 (t, 4H), 6.94-7.02 (m, 8H), 6.36 (d, 4H), 1.72 (s, 12H).

Application Example 1

(9) a) Photoluminescent Characterization in Neat Film

(10) On a silicon substrate, compound (A-1) is vacuum-deposited in a thickness of 50 nm. Absorption, fluorescent spectra (excitation at 531nm) and photoelectron yield spectroscopy of the film are measured, subsequently HOMO and LUMO (eV) of the compound are estimated as 5.71 eV and 3.18 eV, respectively.

(11) b) Photoluminescent Characterization in Host-Guest Film

(12) On a silicon substrate, mCBP doped with 10.2 w % of compound (A-1) is co-deposited in a thickness of 100 nm. The time-resolved and temperature-dependent emission spectra of the host-guest film are measured by photoluminescence spectroscopy with a streak camera. The prompt (˜15 ns) and delayed (>0.5 ms) fluorescent components and the temperature dependency are observed as shown Table 1. The host-guest film shows an emission peak at 525 nm in PL spectrum.

(13) TABLE-US-00001 TABLE 1 Temperature dependence of PL emission of codeposited film (mCBP doped with 10.2 w % of compound (A-1)) (streak camera) Temperature Prompt PL Delayed PL (K) intensity (a.u.) intensity (a.u.)  8 0.82 0.04  68 0.90 0.05 140 0.87 0.15 200 0.96 0.49 250 0.95 0.83 280 1 0.93 198 0.98 1

(14) These results indicate that compound (A-1) is a TADF material.

Application Example 2

(15) An organic light emitting device (OLED) is fabricated by vacuum deposition of ITO (100 nm)/dipyrazino[2,3f:2′,3′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN) (10 nm)/

(16) ##STR00086##
(Tris-Pcz, 30 nm)/89.5 w % 3,3-di(9H-carbazol-9-yl)biphenyl (mCBP):10.5 w % compound A-1 (30 nm)/2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine (T2T, 10 nm)/

(17) ##STR00087##
(Bpy-TP2, 40 nm)/LiF (0.8 nm)/Al (100 nm) on a glass substrate, subsequently the device is encapsulated and the performance of the device is evaluated. The device shows an emission peak at 533 nm in electroluminescence (EL) spectrum with an external quantum efficiency (EQE) of 11.6% which is higher than the theoretical value of conventional fluorescent materials (EQE=5-7.5%).

Application Example 3

(18) Application Example 2 is repeated except that compound A-1 is replaced by compound A-2 with 91.3 w % mCBP:8.7 w % compound A-2. The device shows an emission peak at 531 nm in electroluminescence (EL) spectrum with an external quantum efficiency (EQE) of 9.36%.