LIGHT-EMITTING ELEMENT, LIGHT-EMITTING DEVICE, ELECTRONIC DEVICE, AND LIGHTING DEVICE

• US 20150255742A1
• Filed: 05/21/2015
• Published: 09/10/2015
• Est. Priority Date: 03/26/2013
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: WATABE, Takeyoshi, SEO, Satoshi
• Granted Patent: US 9,461,259 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: C09K 11/025 non-luminescent particle coatings or suspension media
• CPC Class Codes: C09K 11/06 containing organic luminescent materials
• CPC Class Codes: C09K 2211/1007 Non-condensed systems
• CPC Class Codes: C09K 2211/1044 containing two nitrogen atoms as heteroatoms
• CPC Class Codes: C09K 2211/185 of the platinum group, i.e. Os, Ir, Pt, Ru, Rh or Pd
• CPC Class Codes: H10K 2101/10 Triplet emission
• CPC Class Codes: H10K 2101/30 Highest occupied molecular orbital [HOMO], lowest unoccupied molecular orbital [LUMO] or Fermi energy values
• CPC Class Codes: H10K 2101/40 Interrelation of parameters between multiple constituent active layers or sublayers, e.g. HOMO values in adjacent layers
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/125 specially adapted for multicolour light emission, e.g. for emitting white light
• CPC Class Codes: H10K 50/13 comprising stacked EL layers within one EL unit
• CPC Class Codes: H10K 85/342 comprising iridium
• CPC Class Codes: H10K 85/615 Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
• CPC Class Codes: H10K 85/633 comprising polycyclic condensed aromatic hydrocarbons as substituents on the nitrogen atom
• CPC Class Codes: H10K 85/636 comprising heteroaromatic hydrocarbons as substituents on the nitrogen atom
• CPC Class Codes: H10K 85/6572 comprising only nitrogen in the heteroaromatic polycondensed ring system, e.g. phenanthroline or carbazole
• CPC Class Codes: H10K 85/6576 comprising only sulfur in the heteroaromatic polycondensed ring system, e.g. benzothiophene

Abstract

Provided is a light-emitting element having a light-emitting layer which contains at least a host material and a plurality of guest materials, where the host material has a lower T1 level than that of at least one of the plurality of guest materials. The emission of the one of the plurality of guest materials exhibits a multicomponent decay curve, and the lifetime thereof is less than or equal to 15 pec, preferably less than or equal to 10 pec, more preferably less than or equal to 5 pec, where the lifetime is defined as a time for the emission to decrease in intensity to 1/100 of its initial intensity.

Claims

1. A light-emitting device comprising:

a first electrode;

a light-emitting layer over the first electrode, the light-emitting layer comprising a first organic compound, a second organometallic compound, and a third organometallic compound; and

a second electrode over the light-emitting layer,

wherein a T1 level of the first organic compound is lower than a T1 level of the second organometallic compound and higher than a T1 level of the third organometallic compound,

wherein an emission from the second organometallic compound exhibits a multicomponent decay curve, and

wherein a lifetime of the emission is more than or equal to 5 μ

sec and less than or equal to 15 μ

sec where the lifetime is a time required for the emission to decrease in intensity to 1/100 of an initial value thereof.

2. The light-emitting device according to claim 1,

wherein a difference in T1 level between the first organic compound and the second organometallic compound is larger than 0 eV and less than or equal to 0.2 eV.

3. The light-emitting device according to claim 1,

wherein a rate constant of a radiative transition of the third organometallic compound is larger than 5×

10⁵ sec<sup>−

1</sup>.

4. The light-emitting device according to claim 1,

wherein a rate constant of a non-radiative transition of the first organic compound is smaller than 1×

10² sec<sup>−

1</sup>.

5. The light-emitting device according to claim 1,

wherein the first organic compound is selected from a compound having a carbazole skeleton, a compound having a polyazole skeleton, a compound having a quinoxaline skeleton, a compound having a dibenzoquinoxaline skeleton, a compound having a diazine skeleton, and a compound having a pyridine skeleton.

6. The light-emitting device according to claim 1,

wherein the lifetime of the emission is less than or equal to 10 μ

sec.

7. The light-emitting device according to claim 1,

wherein the lifetime of the emission is less than or equal to 5 μ

sec.

8. An electronic device comprising the light-emitting device according to claim 1.

9. A lighting device comprising the light-emitting device according to claim 1.

10. A light-emitting device comprising:

a first electrode;

a light-emitting layer over the first electrode, the light-emitting layer comprising a first organic compound, a second organometallic compound, and a third organometallic compound; and

a second electrode over the light-emitting layer,

wherein a T1 level of the first organic compound is lower than a T1 level of the second organometallic compound and higher than a T1 level of the third organometallic compound,

wherein an emission from the light-emitting layer exhibits a multicomponent decay curve, and

wherein a lifetime of the emission is more than or equal to 5 μ

sec and less than or equal to 15 μ

sec where the lifetime is a time required for the emission to decrease in intensity to 1/100 of an initial value thereof.

11. The light-emitting device according to claim 10,

wherein a difference in T1 level between the first organic compound and the second organometallic compound is larger than 0 eV and less than or equal to 0.2 eV.

12. The light-emitting device according to claim 10,

wherein a rate constant of a radiative transition of the third organometallic compound is larger than 5×

10⁵ sec<sup>−

1</sup>.

13. The light-emitting device according to claim 10,

wherein a rate constant of a non-radiative transition of the first organic compound is smaller than 1×

10² sec<sup>−

1</sup>.

14. The light-emitting device according to claim 10,

wherein the first organic compound is selected from a compound having a carbazole skeleton, a compound having a polyazole skeleton, a compound having a quinoxaline skeleton, a compound having a dibenzoquinoxaline skeleton, a compound having a diazine skeleton, and a compound having a pyridine skeleton.

15. The light-emitting device according to claim 10,

wherein the lifetime of the emission is less than or equal to 10 μ

sec.

16. The light-emitting device according to claim 10,

wherein the lifetime of the emission is less than or equal to 5 μ

sec.

17. An electronic device comprising the light-emitting device according to claim 10.

18. A lighting device comprising the light-emitting device according to claim 10.