Organic electroluminescent device

1. An organic electroluminescent device comprising a light-emitting layer B comprising:

(i) a triplet-triplet annihilation (TTA) material H N , which has a lowermost excited singlet state energy level S1 N and a lowermost excited triplet state energy level T1 N ,

(ii) a thermally activated delayed fluorescence (TADF) material E B , which has a lowermost excited singlet state energy level S1 E and a lowermost excited triplet state energy level T1 E , and

(iii) an organic near-range-charge-transfer (NRCT) emitter S B , which has a lowermost excited singlet state energy level S1 S and a lowermost excited triplet state energy level T1 S ,

wherein the relations expressed by the following formulas (1) to (3) apply:

S 1 E >S 1 S   (1)

S 1 N >S 1 S   (2)

S 1 S <2.95 eV  (3).

2. The organic electroluminescent device according to claim 1 , wherein the TADF material E B exhibits a ΔE ST value, which corresponds to the energy difference between the lowermost excited singlet state (Si) and the lowermost excited triplet state (T1), of less than 0.4 eV; and

wherein the NRCT emitter S B exhibits an emission with a full width at half maximum (FWHM) below 0.35 eV, in PMMA with 5% by weight of the NRCT emitter S B .

3. The organic electroluminescent device according to claim 1 , wherein said organic electroluminescent device is a device selected from the group consisting of an organic light emitting diode, a light emitting electrochemical cell, and a light-emitting transistor.

4. The organic electroluminescent device according to claim 1 , wherein the TADF material E B is an organic TADF material.

5. The organic electroluminescent device according to claim 1 , wherein the device exhibits an emission maximum λ max (D) of 440 to 475 nm.

6. The organic electroluminescent device according to claim 1 , wherein the light-emitting layer B comprises:

(i) 10-96.5% by weight of the host compound H N ;

(ii) 3-50% by weight of the TADF material E B ;

(iii) 0.5-30% by weight of the emitter S B ; and

(iv) optionally 0-74% by weight of one or more solvents.

7. The organic electroluminescent device according to claim 1 , wherein the light-emitting layer B comprises:

(i) 40-74% by weight of the host compound H N ;

(ii) 15-30% by weight of the TADF material E B ;

(iii) 1-5% by weight of the emitter S B ; and

(iv) optionally 0-34% by weight of one or more solvents.

8. The organic electroluminescent device according to claim 1 , wherein the TADF material E B exhibits an emission maximum λ max PMMA (E B ) in the range from 440 to 470 nm.

9. The organic electroluminescent device according to claim 1 , wherein organic near-range-charge-transfer (NRCT) emitter S B comprises a structure according to Formula I-NRCT:

wherein

o is 0 or 1;

m=1−o;

X 1 is N or B;

X 2 is N or B;

X 3 is N or B;

W is selected from the group consisting of Si(R 3S ) 2 , C(R 3S ) 2 , and BR 3S ;

each of R 1S , R 2S , and R 3S is independently selected from the group consisting of:

C 1 -C 5 -alkyl, which is optionally substituted with one or more substituents R 6S ;

C 6 -C 60 -aryl, which is optionally substituted with one or more substituents R 6S ; and

C 3 -C 57 -heteroaryl, which is optionally substituted with one or more substituents R 6S ;

each of R I , R II , R III , R IV , R V , R VI , R VII , R VIII , R IX , R X , and R XI is independently selected from the group consisting of:

hydrogen, deuterium, N(R 5S ) 2 , OR 5S , Si(R 5S ) 3 , B(OR 5S ) 2 , OSO 2 R 5S , CF 3 , CN, halogen,

C 1 -C 40 -alkyl,

which is optionally substituted with one or more substituents R 5S , and

wherein one or more non-adjacent CH 2 -groups are each optionally substituted by R 5S C═CR 5S , C≡C, Si(R 5S S) 2 , Ge(R 5S ) 2 , Sn(R 5S S) 2 , C═O, C═S, C═Se, C═NR 5S , P(═O)(R 5S ), SO, SO 2 , NR 5S , O, S, or CONR 55 ;

C 1 -C 40 -alkoxy,

which is optionally substituted with one or more substituents R 5S , and

wherein one or more non-adjacent CH 2 -groups are each optionally substituted by R 5S C═CR 5S , C≡C, Si(R 5S ) 2 , Ge(R 5S ) 2 , Sn(R 5S S) 2 , C═O, C═S, C═Se, C═NR 5S , P(═O)(R 5S ), SO, SO 2 , NR 5S , O, S, or CONR 55 ;

C 1 -C 40 -thioalkoxy,

which is optionally substituted with one or more substituents R 5S , and

wherein one or more non-adjacent CH 2 -groups are each optionally substituted by R 5S C═CR 5S , C≡C, Si(R 5S ) 2 , Ge(R 5S ) 2 , Sn(R 5S S) 2 , C═O, C═S, C═Se, C═NR 5S , P(═O)(R 5S ), SO, SO 2 , NR 5S , O, S, or CONR 55 ;

C 2 -C 40 -alkenyl,

which is optionally substituted with one or more substituents R 5S , and

wherein one or more non-adjacent CH 2 -groups are each optionally substituted by R 5S C═CR 5S , C≡C, Si(R 5S ) 2 , Ge(R 5S ) 2 , Sn(R 5S S) 2 , C═O, C═S, C═Se, C═NR 5S , P(═O)(R 5S ), SO, SO 2 , NR 5S , O, S, or CONR 55 ;

C 2 -C 40 -alkynyl,

which is optionally substituted with one or more substituents R 5S , and

wherein one or more non-adjacent CH 2 -groups are each optionally substituted by R 5S C═CR 5S , C≡C, Si(R 5S ) 2 , Ge(R 5S ) 2 , Sn(R 5S S) 2 , C═O, C═S, C═Se, C═NR 5S , P(═O)(R 5S ), SO, SO 2 , NR 5S , O, S, or CONR 55 ;

C 6 -C 60 -aryl,

which is optionally substituted with one or more substituents R 5S ; and

C 3 -C 57 -heteroaryl,

which is optionally substituted with one or more substituents R 5S ;

R 5S is at each occurrence independently selected from the group consisting of: hydrogen, deuterium, OPh, CF 3 , CN, F,

C 1 -C 5 -alkyl,

wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF 3 , or F;

C 1 -C 5 -alkoxy,

wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF 3 , or F;

C 1 -C 5 -thioalkoxy,

wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF 3 , or F;

C 2 -C 5 -alkenyl,

wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF 3 , or F;

C 2 -C 5 -alkynyl,

wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF 3 , or F;

C 6 -C 18 -aryl,

which is optionally substituted with one or more C 1 -C 5 -alkyl substituents;

C 3 -C 17 -heteroaryl,

which is optionally substituted with one or more C 1 -C 5 -alkyl substituents;

N(C 6 -C 18 -aryl) 2 ;

N(C 3 -C 17 -heteroaryl) 2 ; and

N(C 3 -C 17 -heteroaryl)(C 6 -C 18 -aryl);

R 6S is at each occurrence independently selected from the group consisting of hydrogen, deuterium, OPh, CF 3 , CN, F,

C 1 -C 5 -alkyl,

wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF 3 , or F;

C 1 -C 5 -alkoxy,

wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF 3 , or F;

C 1 -C 5 -thioalkoxy,

wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF 3 , or F;

C 2 -C 5 -alkenyl,

wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF 3 , or F;

C 2 -C 5 -alkynyl,

wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF 3 , or F;

C 6 -C 18 -aryl,

which is optionally substituted with one or more C 1 -C 5 -alkyl substituents;

C 3 -C 17 -heteroaryl,

which is optionally substituted with one or more C 1 -C 5 -alkyl substituents;

N(C 6 -C 18 -aryl) 2 ;

N(C 3 -C 17 -heteroaryl) 2 ; and

N (C 3 -C 17 -heteroaryl)(C 6 -C 18 -aryl);

wherein two or more of the substituents selected from the group consisting of R I , R II , R III , R IV , R V , R VI , R VII , R VIII , R IX , R X , and R XI that are positioned adjacent to another may optionally each form a ring system with another, wherein the ring system is selected from the group consisting of mono- or polycyclic ring system, aliphatic ring system, aromatic ring system, benzo-fused ring system, and combinations thereof; and

wherein at least one of X 1 , X 2 , and X 3 is B and at least one of X 1 , X 2 , and X 3 is N.

10. The organic electroluminescent device according to claim 9 , wherein X 1 and X 3 each are N and X 2 is B.

11. The organic electroluminescent device according to claim 9 , wherein X 1 and X 3 each are B and X 2 is N.

12. The organic electroluminescent device according to claim 9 , wherein o=0.

13. The organic electroluminescent device according to claim 9 , wherein each of R I , R II , R III , R IV , R V , R VI , R VII , R VIII , R IX , R X , and R XI is independently selected from the group consisting of:

hydrogen, deuterium, halogen, Me, i Pr, t Bu, CN, CF 3 ,

Ph,

which is optionally substituted with one or more substituents independently selected from the group consisting of Me, i Pr, t Bu, CN, CF 3 , and Ph;

pyridinyl,

which is optionally substituted with one or more substituents independently selected from the group consisting of Me, i Pr, t Bu, CN, CF 3 , and Ph;

pyrimidinyl,

which is optionally substituted with one or more substituents independently selected from the group consisting of Me, i Pr, t Bu, CN, CF 3 , and Ph;

carbazolyl,

which is optionally substituted with one or more substituents independently selected from the group consisting of Me, i Pr, t Bu, CN, CF 3 , and Ph;

triazinyl,

which is optionally substituted with one or more substituents independently selected from the group consisting of Me, i Pr, t Bu, CN, CF 3 , and Ph; and

N(Ph) 2 ; and

R 1S and R 2S are each independently selected from the group consisting of

C 1 -C 5 -alkyl,

which is optionally substituted with one or more substituents R 6S ;

C 6 -C 30 -aryl,

which is optionally substituted with one or more substituents R 6S ; and

C 3 -C 30 -heteroaryl,

which is optionally substituted with one or more substituents R 6S .

14. The organic electroluminescent device according to claim 1 , wherein the device exhibits an emission maximum λ max (D) of 450 to 470 nm.

15. A method for generating blue light at a wavelength of from 440 to 475 nm, comprising the steps of:

(i) providing an organic electroluminescent device according to claim 1 ; and

(ii) applying an electrical current to said organic electroluminescent device.