White organic EL element

1. A white organic electroluminescent (EL) element comprising, in sequence:

an anode;

a first light-emitting layer that is a blue-light-emitting layer;

a hole-blocking layer;

an electron transport layer; and

a cathode,

wherein the hole-blocking layer is adjacent to the first light-emitting layer and the electron transport layer,

the first light-emitting layer contains a first host and a first dopant that emits blue fluorescent light,

the hole-blocking layer is formed of a hydrocarbon,

the electron transport layer is formed of a nitrogen-containing heterocyclic compound,

the first host and the first dopant satisfy relation (a), and

the hole-blocking layer and the electron transport layer satisfy relation (b) and relation (c):

LUMO( H 1)>LUMO( D 1)  (a)

0.1< d (ETL)/ d (HBL)<0.7  (b)

90 nm≤ d ( E )= d (HBL)+ d (ETL)<150 nm,  (c)

where LUMO (H1) is a lowest unoccupied molecular orbital (LUMO) energy of the first host,

LUMO (D1) is a LUMO energy of the first dopant,

d (HBL) is a thickness of the hole-blocking layer,

d (ETL) is a thickness of the electron transport layer, and

d (E) is a total thickness of an electron supply layer composed of the hole-blocking layer and the electron transport layer.

2. The white organic EL element according to claim 1 , wherein the hole-blocking layer is formed of an aromatic hydrocarbon, and the aromatic hydrocarbon has a molecular structure constituted by an aromatic hydrocarbon ring selected from the group consisting of a benzene ring, a naphthalene ring, a fluorene ring, a benzofluorene ring, a phenanthrene ring, a chrysene ring, and a triphenylene ring, and optionally has an alkyl group having 1 to 12 carbon atoms.

3. The white organic EL element according to claim 1 , further comprising, between the anode and the first light-emitting layer, a hole supply layer including a hole transport layer, wherein the hole supply layer and the electron supply layer satisfy relation (d):

2.0< d ( E )/ d ( H )<6.0  (d)

where d (E) is a total thickness of the electron supply layer, and

d (H) is a total thickness of the hole supply layer.

4. The white organic EL element according to claim 1 , further comprising, between the anode and the first light-emitting layer, a second light-emitting layer and a third light-emitting layer,

wherein the second light-emitting layer contains a second host and a second dopant that emits fluorescent light,

the third light-emitting layer contains a third host and a third dopant that emits fluorescent light,

the second host and the second dopant satisfy relation (e), and the third host and the third dopant satisfy relation (f):

LUMO( H 2)>LUMO( D 2)  (e)

LUMO( H 3)>LUMO( D 3)  (f)

where LUMO (H2) is a LUMO energy of the second host,

LUMO (D2) is a LUMO energy of the second dopant,

LUMO (H3) is a LUMO energy of the third host, and

LUMO (D3) is a LUMO energy of the third dopant.

5. The white organic EL element according to claim 4 , wherein the first host, the second host, or the third host is a hydrocarbon.

6. The white organic EL element according to claim 4 , wherein the first dopant, the second dopant, or the third dopant is a compound having a fluoranthene skeleton.

7. The white organic EL element according to claim 1 , further comprising a second light-emitting layer between the anode and the first light-emitting layer,

wherein the second light-emitting layer contains a second host, a second dopant that emits fluorescent light, and a third dopant that emits fluorescent light,

the second host and the second dopant satisfy relation (g), and the second host and the third dopant satisfy relation (h):

LUMO( H 2)>LUMO( D 2)  (g)

LUMO( H 2)>LUMO( D 3)  (h)

where LUMO (H2) is a LUMO energy of the second host,

LUMO (D2) is a LUMO energy of the second dopant, and

LUMO (D3) is a LUMO energy of the third dopant.

8. The white organic EL element according to claim 7 , wherein the first host or the second host is a hydrocarbon.

9. The white organic EL element according to claim 1 , further comprising an electron injection layer between the cathode and the electron transport layer.

10. The white organic EL element according to claim 9 , wherein the electron injection layer contains an alkali metal or an alkaline earth metal.

11. A display device comprising a plurality of pixels, wherein at least one of the pixels includes the white organic EL element according to claim 1 and an active element connected to the white organic EL element.

12. An image capture apparatus comprising:

an optical unit including a plurality of lenses;

an image capture element configured to receive light that has passed through the optical unit; and

a display unit,

wherein the display unit is configured to display information acquired by the image capture element and includes the display device according to claim 11 .

13. An electronic device comprising:

a housing;

a communication unit configured to communicate with an external device; and

a display unit,

wherein the display unit is the display device according to claim 11 .

14. A lighting device comprising:

a light source; and

a light diffusion unit or an optical filter,

wherein the light source includes the white organic EL element according to claim 1 .

15. A moving object comprising:

a body; and

a lighting fixture mounted to the body,

wherein the lighting fixture includes the white organic EL element according to claim 1 .