Organic electroluminescent device emitting blue light

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

(i) a host material H N , which has a lowermost excited singlet state energy level S1 N , a lowermost excited triplet state energy level T1 N , a highest occupied molecular orbital HOMO(H N ) having an energy E HOMO (H N ) and a lowest unoccupied molecular orbital LUMO(H N ) having an energy E LUMO (H N );

(ii) a host material H P , which has a lowermost excited singlet state energy level S1 P and a lowermost excited triplet state energy level T1 P , a highest occupied molecular orbital HOMO(H P ) having an energy E HUMO (H P ) and a lowest unoccupied molecular orbital LUMO(H P ) having an energy E HUMO (H P );

(iii) 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 , a highest occupied molecular orbital HOMO(E E ) having an energy E HOMO (E E ) and a lowest unoccupied molecular orbital LUMO(E E ) having an energy E LUMO (E E ); and

(iv) a small full width at half maximum (FWHM) emitter S B , which has a lowermost excited singlet state energy level S1 S and a lowermost excited triplet state energy level T1 S , a highest occupied molecular orbital HOMO(E S ) having an energy E HOMO (E S ) and a lowest unoccupied molecular orbital LUMO(E S ) having an energy E LUMO (E S ), wherein S B emits light with an emission maximum λ max PMMA (S) of 440 nm to 475 nm,

wherein the relations expressed by the following formulas (1) to (3) and at least one of (4a) or (4b) apply:

S 1 N >S 1 E   (1),

S 1 P >S 1 E   (2),

E LUMO ( H N )− E HOMO ( H P )> S 1 E   (3),

E LUMO ( H P )− E LUMO ( H N )≥0.2 eV  (4a),

E HOMO ( H P ) −E HOMO ( H N )≥0.2 eV  (4b),

and wherein the relations expressed by the following formulas (5) to (8) apply:

S 1 N >S 1 S   (5),

S 1 P >S 1 S   (6),

S 1 E >S 1 S   (7),

S 1 S <2.95 eV  (8).

2. 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.

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

4. The organic electroluminescent device according to claim 1 , wherein formulas (4a) and (4b) apply.

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 5 , wherein the device exhibits an emission maximum λ max (D) of 450 to 470 nm.

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

(i) 10-84% by weight of the host compound H P ;

(ii) 10-84% by weight of the host compound H N ;

(iii) 5-50% by weight of the TADF material E B ; and

(iv) 1-10% by weight of the emitter S B ; and optionally

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

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

(i) 10-30% by weight of the host compound H P ;

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

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

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

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

9. 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.

10. The organic electroluminescent device according to claim 1 , wherein the small FWHM emitter S B is an organic near-range-charge-transfer (NRCT) emitter.

11. The organic electroluminescent device according to claim 1 , wherein the small FWHM emitter S B comprises or consists of a structure according to Formula I:

wherein

n is 0 or 1;

m=1−n;

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 3 ) 2 , C(R 3 ) 2 and BR 3 ;

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

C 1 -C 5 -alkyl,

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

C 6 -C 60 -aryl,

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

C 3 -C 57 -heteroaryl,

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

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 from another selected from the group consisting of:

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

C 1 -C 40 -alkyl,

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

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

C 1 -C 40 -alkoxy,

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

wherein one or more non-adjacent CH 2 -groups are each optionally substituted by R 5 C═CR 5 , C≡C,

Si(R 5 ) 2 , Ge(R 5 ) 2 , Sn(R 5 ) 2 , C═O, C═S, C═Se, C═NR 5 , P(═O)(R 5 ), SO, SO 2 , NR 5 , O, S or CONR 5 ;

C 1 -C 40 -thioalkoxy,

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

wherein one or more non-adjacent CH 2 -groups are each optionally substituted by R 5 C═CR 5 , C≡C,

Si(R 5 ) 2 , Ge(R 5 ) 2 , Sn(R 5 ) 2 , C═O, C═S, C═Se, C═NR 5 , P(═O)(R 5 ), SO, SO 2 , NR 5 , O, S or CONR 5 ;

C 2 -C 40 -alkenyl,

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

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

C 2 -C 40 -alkynyl,

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

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

C 6 -C 60 -aryl,

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

C 3 -C 57 -heteroaryl,

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

R 5 is at each occurrence independently from another 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 from each other substituted by deuterium, CN, CF 3 , or F;

C 1 -C 5 -alkoxy,

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

C 1 -C 5 -thioalkoxy,

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

C 2 -C 5 -alkenyl,

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

C 2 -C 5 -alkynyl,

wherein optionally one or more hydrogen atoms are independently from each other 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 6 is at each occurrence independently from another 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 from each other substituted by deuterium, CN, CF 3 , or F;

C 1 -C 5 -alkoxy,

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

C 1 -C 5 -thioalkoxy,

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

C 2 -C 5 -alkenyl,

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

C 2 -C 5 -alkynyl,

wherein optionally one or more hydrogen atoms are independently from each other 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 each form a ring system with another, said ring system selected from the group consisting of a mono- or polycyclic, aliphatic, aromatic and benzo-fused ring system; 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.

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

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

14. The organic electroluminescent device according to claim 11 , wherein n=0.

15. The organic electroluminescent device according to claim 11 , 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 from another 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 from each other 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 from each other 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 from each other 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 from each other 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 from each other selected from the group consisting of Me, i Pr, t Bu, CN, CF 3 , and Ph,

and N(Ph) 2 ; and

R 1 and R 2 is each independently from each other selected from the group consisting of

C 1 -C 5 -alkyl,

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

C 6 -C 30 -aryl,

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

C 3 -C 30 -heteroaryl,

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

16. 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.