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US-12622170-B2 - Fluorescent organic light emitting elements having high efficiency

US12622170B2US 12622170 B2US12622170 B2US 12622170B2US-12622170-B2

Abstract

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

Inventors

  • Junichi Tanabe
  • Christian Lennartz

Assignees

  • UDC IRELAND LIMITED

Dates

Publication Date
20260505
Application Date
20230714
Priority Date
20140519

Claims (18)

  1. 1 . A compound of formula I wherein X is independently in each occurrence O, S or NR 9 , Y 1 , Y 2 , Y 3 and Y 4 are independently of each other a direct bond, or a group of formula -[A 1 ]-[A 2 ] y -, wherein A 1 and A 2 are independently of each other —CH═CH—, —C≡C— or a C 6 -C 10 arylene group, which may optionally be substituted by one or more C 1 -C 25 alkyl groups; y is 0, or 1; R 1 , R 2 , R 3 and R 4 are independently of each other H, D, F, Cl, a C 1 -C 25 alkyl group, a C 1 -C 25 alkoxy group, a C 6 -C 10 aryloxy group, or a donor group of formula X 1 is O, S, N(R 15 ), C(═O), C(R 16 )(R 17 ), B(R 18 ), or Si(R 19 )(R 20 ), R 9 is H, a C 1 -C 25 alkyl group, or a C 6 -C 10 aryl group; R 10 , R 11 , R 21 and R 21′ are independently of each other H, D, F, Cl, or a C 1 -C 25 alkyl group; R 15 , R 16 , R 17 , R 18 , R 19 and R 20 are independently of each other H, D, a C 1 -C 25 alkyl group, or a C 6 -C 14 aryl group, which can optionally be substituted by one, or more groups selected from a C 1 -C 25 alkyl group, a C 1 -C 25 alkoxy group and a C 6 -C 10 aryloxy group; provided that all of conditions (i) to (iii) are satisfied: (i) at least one donor group of formula (Xa) or (Xd) is present in the compound of formula (I); (ii) if Y 2 and Y 4 each represents C 6 arylene, then X 1 is NR 15 , (C═O), C(R 16 )(R 17 ), B(R 18 ), or Si(R 19 )(R 20 ), wherein R 16 , R 17 , R 19 , and R 20 are not methyl and R 15 is not methyl or a C 6 -C 14 aryl group; and (iii) the compound of Formula (I) is not represented by compound (A-1), (A-2), (A-5), (A-6), (A-8), (B-1), (B-2), (B-5), (B-6), or (B-8):
  2. 2 . The compound according to claim 1 , wherein the compound is a compound of any of formula (Ia) to (If) wherein Y 1 , Y 2 , Y 3 , Y 4 , R 1 , R 2 , R 3 and R 4 are as defined in claim 1 .
  3. 3 . The compound according to claim 2 , wherein the compound of formula (I) is a compound of formula (Ia), (Ib), (Ic), (Id), (Ie), or (If), wherein Y 1 and Y 3 are a direct bond; R 1 and R 3 are H; Y 2 and Y 4 are a direct bond, or a group of formula R 2 and R 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 2 and Y 4 are a direct bond; R 2 and R 4 are H; Y 1 and Y 3 are a direct bond, or a group of formula R 1 and R 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 4 is a direct bond, or a group of formula R 4 is a donor group of formula (Xa), or (Xd); Y 2 is a group of formula R 2 is H; Y 1 and Y 3 are a direct bond; R 1 and R 3 are H; or a compound of formula (Ia), (Ib), (Ic), (Id), (Ie), or (If), wherein Y 1 is a direct bond, or a group of formula R 1 is a donor group of formula (Xa), or (Xd); Y 2 , Y 3 and Y 4 are a group of formula R 2 , R 3 and R 4 are H, wherein the donor group (Xa) is a group of formula and the donor group (Xd) is a group of formula
  4. 4 . The compound according to claim 1 wherein Y 1 , Y 2 , Y 3 and Y 4 are independently of each other a direct bond, or a group of formula
  5. 5 . The compound according to claim 1 , wherein R 1 , R 2 , R 3 and R 4 are independently of each other H, a C 1 -C 25 alkyl group, a C 1 -C 25 alkoxy group, a C 6 -C 10 aryloxy group, a donor group of formula X 1 is O, S, C(O), N(R 15 ), or C(R 16 )(R 17 ); and R 10 , R 11 , R 21 and R 21′ are independently of each other H, or a C 1 -C 25 alkyl group; R 15 is a group of formula R 16 and R 17 are independently of each other H, a C 1 -C 25 alkyl group; R 22 and R 23 are independently of each other H, a C 1 -C 25 alkyl group, a C 1 -C 25 alkoxy group, or a C 6 -C 10 aryloxy group; with the proviso that at least one of R 1 , R 2 , R 3 and R 4 is a donor group of formula (Xa) or (Xd).
  6. 6 . The compound according to claim 5 , wherein the donor group is a donor group of formula (Xa), wherein X 1 is O, S, C(CH 3 )(CH 3 ), C(═O), or a donor group of formula (Xd), wherein R 21 and R 21′ are H.
  7. 7 . The compound according to claim 1 , wherein the donor group is a group of formula
  8. 8 . The compound according to claim 1 , wherein the compound exhibits delayed fluorescence emission.
  9. 9 . The compound according to claim 1 , wherein X is NR 9 .
  10. 10 . A light-emitting layer comprising the compound according to claim 1 .
  11. 11 . An organic light emitting element, comprising the compound of formula (I) according to claim 1 .
  12. 12 . The organic light-emitting element according to claim 11 , 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).
  13. 13 . The organic light-emitting element according to claim 11 , 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).
  14. 14 . The organic light-emitting element according to claim 11 , wherein the organic light-emitting element emits delayed fluorescence.
  15. 15 . 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 .
  16. 16 . An organic light emitting element comprising a compound of formula (I); and an organic compound having a higher value of at least one of excited singlet energy and excited triplet energy than the compound of formula (I); wherein X is independently in each occurrence O, S or NR 9 , Y 1 , Y 2 , Y 3 and Y 4 are independently of each other a direct bond, or a group of formula -[A 1 ]-[A 2 ] y -, wherein A 1 and A 2 are independently of each other —CH═CH—, —C≡C— or a C 6 -C 10 arylene group, which may optionally be substituted by one or more C 1 -C 25 alkyl groups; y is 0, or 1; R 1 , R 2 , R 3 and R 4 are independently of each other H, D, F, Cl, a C 1 -C 25 alkyl group, a C 1 -C 25 alkoxy group, a C 6 -C 10 aryloxy group, or a donor group of formula X 1 is O, S, N(R 15 ), C(═O), C(R 16 )(R 17 ), B(R 18 ), or Si(R 19 )(R 20 ), R 9 is H, a C 1 -C 25 alkyl group, or a C 6 -C 10 aryl group; R 10 , R 11 , R 21 and R 21′ are independently of each other H, D, F, Cl, or a C 1 -C 25 alkyl group; R 15 , R 16 , R 17 , R 18 , R 19 and R 20 are independently of each other H, D, a C 1 -C 25 alkyl group, or a C 6 -C 14 aryl group, which can optionally be substituted by one, or more groups selected from a C 1 -C 25 alkyl group, a C 1 -C 25 alkoxy group and a C 6 -C 10 aryloxy group; provided that all of conditions (i) to (iii) are satisfied: (i) at least one donor group of formula (Xa) or (Xd) is present in the compound of formula (I); (ii) if Y 2 and Y 4 each represents C 6 arylene, then X 1 is NR 15 , (C═O), C(R 16 )(R 17 ), B(R 18 ), or Si(R 19 )(R 20 ), wherein R 16 , R 17 , R 19 , and R 20 are not methyl and R 15 is not methyl or a C 6 -C 14 aryl group; and (iii) the compound of Formula (I) is not represented by compound (A-1), (A-2), (A-5), (A-6), (A-8), (B-1), (B-2), (B-5), (B-6), or (B-8):
  17. 17 . The organic light emitting element according to claim 16 , wherein the organic compound has a higher excited triplet energy than the compound of formula (I).
  18. 18 . The organic light emitting element according to claim 16 , wherein the compound of formula (I) and the organic compound having a higher value of at least one of excited singlet energy and excited triplet energy than the compound of formula (I) are each present in a light-emitting layer.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. application Ser. No. 16/792,983, filed Feb. 18, 2020, now allowed, which is a continuation of U.S. application Ser. No. 15/312,115, filed Nov. 17, 2016, now U.S. Pat. No. 10,586,930, which is a U.S. National Stage Application filed under 35 U.S.C. § 371 claiming benefit to International Patent Application No. PCT/EP2015/060305, filed May 11, 2015, which is entitled to priority under 35 U.S.C. § 119 (a)-(d) to EP Application Serial No. 14168826.7, filed May 19, 2014, each of which is hereby incorporated by reference in its entirety. The present invention relates to organic light emitting elements, comprising thermally activated delayed fluorescence (TADF) emitters and/or hosts of formula (I), which have a sufficiently small energy gap between S1 and T1 (ΔEST) to enable up-conversion of the triplet exciton from T1 to S1. The organic light emitting elements show high electroluminescent efficiency. The development of OLED luminescent materials is an important issue and these materials have been classified into two major categories. The first is fluorescent materials, which can harvest only the singlet excitons (25%) that are generated by electrical excitation. The second is phosphorescent materials, which can harvest the triplet excitons generated (75%). The branching ratio of singlet and triplet excitons is 1:3. Therefore, in recent devices, phosphorescent materials and their related technologies have been indispensable to obtain high EL efficiency. However, phosphorescent materials generally contain a rare metal element such as Ir or Pt. These metals are rather expensive and are dependent on limited global resources. Recently, the alternative concept of thermally activated delayed fluorescence (TADF) as a third generation luminescent material, instead of the conventional fluorescent and phosphorescent materials was described by C. Adachi et al. in Adv. Mater., 2009, 21, 4802; Appl. Phys. Lett., 2011, 98, 083302 and Chem. Commun., 2012, 48, 9580. The TADF strongly depends on HOMO-LUMO separation in a single molecule. TADF materials have a sufficiently small energy gap between S1 and T1 (ΔEST) to enable up-conversion of the triplet exciton from T1 to S1. This small ΔEST enables TADF materials to realize 100% of the exciton formation generated by electrical excitation at S1. WO2011105700 relates to an electroluminescent compound represented by formula 1 or 2: wherein R1 through R5 independently represent hydrogen, (C1-C60)alkyl, (C3-C60)cycloalkyl, (C6-C60)aryl, (C2-60)heteroaryl containing one or more heteroatom(s) selected from N, O, S, P, Si and Se, (C1-60)alkoxy, (C1-C60)alkylthio, (C6-60)aryloxy, (C6-C60)arylthio, (C6-30)aryl(C1-C30)alkylamino, tri(C1-C30)alkylsilyl, di(C1-C30)alkyl(C6-C30)arylsilyl or tri(C6-C30)arylsilyl;X represents a chemical bond, —(CR6R7)m—, —N(R8)—, —Si(R8)(R10)—, —O—, —S—, —Se— or —(CR11)C═C(R12)—;R6 through R12 independently represent hydrogen, (C1-C60)alkyl, (C3-C60)cycloalkyl, (C6-C60)aryl, (C2-60)heteroaryl containing one or more heteroatom(s) selected from N, O, S, Si and Se, (C1-60)alkoxy, (C1-C60)alkylthio, (C6-60)aryloxy, (C6-C60)arylthio, mono- or di(C1-60)alkylamino, mono- or di(C6-60)arylamino, (C6-30)aryl(C1-C30)alkylamino, tri(C1-C30)alkylsilyl, di(C1-C30)alkyl(C6-C30)arylsilyl or tri(C6-C30)arylsilyl, or R6 and R7, R9 and R10, and R11 and R12 are linked via (C3-C60)alkylene or (C3-C60)alkenylene with or without a fused ring to form an aliphatic ring or a mono- or polycyclic aromatic ring;Y represents (C6-C60)arylene, adamantylene, (C3-C60)heteroarylene containing one or more heteroatom(s) selected from N, O, S, P, Si and Se, or . . . ; and their use in organic light emitting devices as fluorescent dopant. The synthesis of 2,2′-diphenothiazin-10-yl-1,1′benzo[1,2-d,4,5-d]bisoxazole-2,6-diyl-bisethanone is described in M. A. El-Maghraby, M. A. Abbady, Journal of the Indian Chemical Society 55 (1978) 44-47. In Tae Kim et al., Synthetic Metals 156 (2006) 38-41 reports that Stille coupling reaction of 4,8-dibromo-2,6-dihexyl-benzo[1,2-d:4,5-d′]bisthiazole and 2,5-bis(trimethylstannyl)thiophene afford a new conjugated conducting copolymer 1. JP10340786 relates to compounds for use in an organic electroluminescent element represented by formulas such as, for example, In the formulas X1 and X2 independently represent N or CH, Y1 and Y2 independently represent S, O, N—Z, Z is a hydrogen atom, a substituted or non-substituted alkyl group, a substituted or non-substituted cycloalkyl group, a substituted or non-substituted heterocyclic group. R1-R4 independently represent respectively a hydrogen atom, a halogen atom, a cyano group, a nitro group, a substituted or non-substituted alkyl group, a substituted or non-substituted aryl group, a substituted or non-substituted alkoxy group, a substituted or non-substituted aryl oxy group, a substituted or non-substituted alkyl thio group, a substituted or non