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 on basis of phthalimide and naphthalimide materials, 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) ##STR00109## wherein X is O, or NR.sup.2; R.sup.1 is a C.sub.1-C.sub.25alkyl group, a C.sub.6-C.sub.10aryl group which is optionally substituted by one or more groups R.sup.8; R.sup.2 is a C.sub.1-C.sub.6alkyl group, a C.sub.2-C.sub.4alkenyl group, or a C.sub.6-C.sub.10aryl group, which is optionally substituted by one or more groups R.sup.8; or R.sup.1 and R.sup.2 together form a ring ##STR00110## wherein R.sup.37, R.sup.38, R.sup.39 and R.sup.40 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.10aryl group which may optionally be substituted by one or more groups R.sup.8, A.sup.1, A.sup.2 and A.sup.3 are C, x is 0, or 1, if x is 0, A.sup.1 and A.sup.3 are connected via a double bond and together form a ring ##STR00111## if x is 1, A.sup.1 and A.sup.2 and A.sup.2 and A.sup.3 are connected via a single bond and together form a ring system ##STR00112## R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.31, R.sup.32, R.sup.33, R.sup.34, R.sup.35 and R.sup.36 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.10aryl group which may optionally be substituted by one or more groups R.sup.8, or a donor group of formula ##STR00113## R.sup.8 is D, F, Cl, a C.sub.1-C.sub.12alkyl group, a C.sub.1-C.sub.12alkoxy group, or a C.sub.6-C.sub.10aryl group; X.sup.1 is a direct bond, 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.10, R.sup.11, R.sup.21 and R.sup.21′ are independently of each other H, D, F, Cl, Br, 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 of the groups R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.31, R.sup.32, R.sup.33, R.sup.34, R.sup.35 and R.sup.36 is a donor group of formula (Xa), or (Xd).

2. The compound according to claim 1, wherein the compound is a compound of formula (II) ##STR00114## wherein X, R.sup.1, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are as defined in claim 1.

3. The compound according to claim 2, wherein the compound is a compound of formula (IIa) ##STR00115## wherein R.sup.1, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are as defined in claim 1.

4. The compound according to claim 1, wherein R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are independently of each other a donor group of formula (Xa), or (Xd) as defined in claim 1; or R.sup.3 and R.sup.6 are H and R.sup.4 and R.sup.5 are independently of each other a donor group of formula (Xa), or (Xd) as defined in claim 1; or R.sup.4 and R.sup.5 are H and R.sup.3 and R.sup.6 are independently of each other a donor group of formula (Xa), or (Xd) as defined in claim 1; or R.sup.4 and R.sup.6 are H and R.sup.3 and R.sup.5 are independently of each other a donor group of formula (Xa), or (Xd) as defined in claim 1; or R.sup.3, R.sup.4 and R.sup.6 are H and R.sup.5 is a donor group of formula (Xa), or (Xd) as defined in claim 1; or R.sup.3, R.sup.4 and R.sup.5 are H and R.sup.6 is a donor group of formula (Xa), or (Xd) as defined in claim 1.

5. The compound according to claim 2, wherein the compound is a compound of formula (IIb) ##STR00116## wherein R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are as defined in claim 1.

6. The compound according to claim 5, wherein R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are independently of each other a donor group of formula (Xa), or (Xd) as defined in claim 1; or R.sup.3 and R.sup.6 are H and R.sup.4 and R.sup.5 are independently of each other a donor group of formula (Xa), or (Xd) as defined in claim 1; or R.sup.4 and R.sup.5 are H and R.sup.3 and R.sup.6 are independently of each other a donor group of formula (Xa), or (Xd) as defined in claim 1; or R.sup.3, R.sup.4 and R.sup.6 are H and R.sup.5 is a donor group of formula (Xa), or (Xd) as defined in claim 1; or R.sup.3, R.sup.4 and R.sup.6 are H and R.sup.5 is a donor group of formula (Xa), or (Xd) as defined in claim 1; or R.sup.3, R.sup.5 and R.sup.6 are H and R.sup.4 is a donor group of formula (Xa), or (Xd) as defined in claim 1; or R.sup.4, R.sup.5 and R.sup.6 are H and R.sup.3 is a donor group of formula (Xa), or (Xd) as defined in claim 1.

7. The compound according to claim 1, wherein the compound is a compound of formula (III) ##STR00117## wherein X, R.sup.1, R.sup.31, R.sup.32, R.sup.33, R.sup.34, R.sup.35 and R.sup.36 are as defined in claim 1.

8. The compound according to claim 7, wherein the compound is a compound of formula (IIIa) ##STR00118## wherein R.sup.1, R.sup.31, R.sup.32, R.sup.33, R.sup.34, R.sup.35 and R.sup.36 are as defined in claim 1.

9. The compound according to claim 8, wherein R.sup.31, R.sup.32, R.sup.33, R.sup.35 and R.sup.36 are H and R.sup.34 is a donor group of formula (Xa), or (Xd) as defined in claim 1; or R.sup.31, R.sup.32, R.sup.33, R.sup.34 and R.sup.36 are H and R.sup.35 is a donor group of formula (Xa), or (Xd) as defined in claim 1; or R.sup.31, R.sup.32, R.sup.33, R.sup.34 and R.sup.35 are H and R.sup.36 is a donor group of formula (Xa), or (Xd) as defined in claim 1; or R.sup.31, R.sup.32, R.sup.35 and R.sup.36 are H and R.sup.33 and R.sup.34 are independently of each other a donor group of formula (Xa), or (Xd) as defined in claim 1; R.sup.32 and R.sup.35 are H and R.sup.31, R.sup.33, R.sup.34 and R.sup.36 are independently of each other a donor group of formula (Xa), or (Xd) as defined in claim 1; or R.sup.31, R.sup.32, R.sup.33, R.sup.34, R.sup.35 and R.sup.36 are independently of each other a donor group of formula (Xa), or (Xd) as defined in claim 1.

10. The compound according to claim 7, wherein the compound is a compound of formula (IIIb) ##STR00119## wherein R.sup.31, R.sup.32, R.sup.33, R.sup.34, R.sup.35 and R.sup.36 are as defined in claim 1.

11. The compound according to claim 10, wherein R.sup.31, R.sup.32, R.sup.34, R.sup.35 and R.sup.36 are H and R.sup.33 is a donor group of formula (Xa), or (Xd) as defined in claim 1; or R.sup.31, R.sup.32, R.sup.34, R.sup.35 and R.sup.36 are H and R.sup.33 is a donor group of formula (Xa), or (Xd) as defined in claim 1; or R.sup.31, R.sup.32, R.sup.35 and R.sup.36 are H and R.sup.33 and R.sup.34 are independently of each other a donor group of formula (Xa), or (Xd) as defined in claim 1.

12. The compound according to claim 1, wherein R.sup.1 is a C.sub.1-C.sub.25alkyl group, a group of formula ##STR00120## wherein R.sup.41 and R.sup.42 are a C.sub.1-C.sub.8alkyl group; R.sup.43 is a C.sub.1-C.sub.8alkyl group, or a C.sub.1-C.sub.8alkoxy group; R.sup.44 is a C.sub.1-C.sub.8alkyl group, or a phenyl group; and R.sup.45 is a C.sub.1-C.sub.8alkyl group.

13. The compound according to claim 1, wherein the donor group is a donor group of formula (Xa), wherein X.sup.1 is a direct bond, O, S, C(CH.sub.3)(CH.sub.3), C(═O), or ##STR00121## and R.sup.10 and R.sup.11 are as defined in claim 1; or a donor group of formula (Xd), wherein R.sup.21 and R.sup.21′ are H.

14. The compound according to claim 1, wherein the donor group is a group of formula ##STR00122##

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

16. An organic light emitting element, comprising the compound according to claim 1.

17. The organic light-emitting element according to claim 16, comprising a light-emitting layer comprising a compound according to claim 1 as guest and a host material.

18. The organic light-emitting element according to claim 16, comprising a light-emitting layer comprising a compound according to claim 1 as host and a guest material.

19. The organic light-emitting element according to claim 16, characterized in that it emits delayed fluorescence.

20. 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.

21. Use of the compound according to claim 1 for generating delayed fluorescence emission.

Description

EXAMPLES

Example 1

[0156] ##STR00102##

[0157] a) The compound 1a is prepared from 4-bromo-1,8-naphthalenedicarboxylic acid anhydride and 2,6-diisopropylaniline according to the synthetic procedure described in Organic Letters, 13(20) (2011) 5532-5535.

##STR00103##

[0158] b) The product from example 1a (2.29 mmol), dimethylacridine (2.29 mmol), tris(dibenzylideneacetone) dipalladium (0.046 mmol), tri-tert-buthylphosphine (0.092 mmol), sodium t-buthoxide (3.44 mmol) and 12.5 ml of toluene are placed in a 50 ml flask. The mixture is stirred at 110° C. overnight and cooled. The mixture is washed with H.sub.2O and sat. NaCl.sub.aq, then the aqueous layer is extracted with ethyl acetate. The combined organic layer is dried over MgSO4 subsequently concentrated under reduced pressure. A orange solid, compound (B-4), is obtained by washing with hexane and drying in vacuum. (Yield: 80.5%). The product is subsequently purified using zone sublimation. .sup.1H-NMR (ppm, CDCl.sub.3): 8.86 (d, 1H), 8.68 (d, 1H), 8.12 (d, 1H), 7.84 (d, 1H), 7.68 (td, 1H), 7.55 (dd, 2H), 7.49 (d, 1H), 7.36 (d, 2H), 6.97 (td, 2H), 6.90 (td, 2H), 6.04 (dd, 2H), 2.83 (m, 2H), 1.85 (s, 3H), 1.80 (s, 3H), 1.2 (t, 12H).

Example 2

[0159] ##STR00104##

[0160] The compound B-1 is prepared according to the method described in Example 1 using carbazole in place of dimethylacridine.

[0161] .sup.1H-NMR (ppm, CDCl.sub.3): 8.86 (d, 1H), 8.73 (d, 1H), 8.24 (d, 2H), 7.97 (d, 1H), 7.88 (d, 1H), 7.68 (t, 1H), 7.51 (t, 1H), 7.38 (m, 6H), 7.11 (d, 2H), 2.83 (m, 2H), 1.21 (t, 12H).

Example 3

[0162] ##STR00105##

[0163] The compound B-13 is prepared according to the method described in Example 1 using 3-bromo-7H-benzimidazo[2,1-a]benz[de]isoquinoline-7-one in place of the compound 1a.

[0164] .sup.1H-NMR (ppm, CDCl.sub.3): 9.08 (d, 1H), 8.86 (d, 1H), 8.61 (m, 1H), 8.14 (d, 1H), 7.94 (m, 1H), 7.86 (d, 1H), 7.72 (t, 1H), 7.54 (m, 4H), 6.96 (t, 2H), 6.88 (t, 2H), 6.03 (d, 2H), 1.87 (s, 3H), 1.78 (s, 3H).

Application Example 1

a) Photoluminescent Characterization in Neat Film

[0165] On a silicon substrate, compound

##STR00106##

is vacuum-deposited in a thickness of 50 nm. Absorption, fluorescent spectra (excitation at 354 nm) and photoelectron yield spectroscopy of the film are measured, subsequently HOMO and LUMO (eV) of the compound are estimated as 6.14 eV and 3.90 eV, respectively.

b) Photoluminescent Characterization in Host-Guest Film

[0166] On a silicon substrate, mCBP doped with 9.8 w % of compound (B-4) is co-deposited in a thickness of 60 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 (0-15 ns) and delayed (0.1-2 ms) fluorescent components and the temperature dependency are observed as shown Table 1. The host-guest film shows an emission peak at 601 nm in PL spectrum.

TABLE-US-00001 TABLE 1 Temperature dependence of PL emission of co-deposited film (mCBP doped with 9.8 w % of compound (B-4)) (streak camera) Temperature (K.) Prompt PL intensity (a.u.) Delayed PL intensity (a.u.) 8 0.875 0.060 68 0.833 0.256 139 0.875 0.720 199 0.938 0.970 249 0.917 1 279 1 0.976 298 0.958 0.958

[0167] These results indicate that compound (B-4) is a TADF material.

Application Example 2

[0168] An organic light emitting device (OLED) is fabricated by vacuum deposition of ITO (100 nm)/dipyrazino[2,3-f:2′,3′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN) (10 nm)/

##STR00107##

(Tris-PCz, 30 nm)/89.3 w % 3,3-di(9H-carbazol-9-yl)biphenyl (mCBP):10.7 w % compound B-4 (30 nm)/2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine (T2T, 10 nm)/

##STR00108##

(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 616 nm in elec-troluminescence (EL) spectrum with an external quantum efficiency (EQE) of 7.5%.