Light-emitting element, light-emitting device, display device, electronic device, and lighting device
First Claim
Patent Images
1. A light-emitting element comprising:
- a first phosphorescent compound;
a second phosphorescent compound; and
a third phosphorescent compound,wherein the first phosphorescent compound emits blue light,wherein ε
(λ
)λ
4 of the second phosphorescent compound has a peak within a wavelength range of 440 nm to 520 nm,wherein a peak wavelength of the second phosphorescent compound is longer than a peak wavelength of the first phosphorescent compound,wherein ε
(λ
)λ
4 of the third phosphorescent compound has a peak within a wavelength range of 520 nm to 600 nm,wherein a peak wavelength of the third phosphorescent compound is longer than the peak wavelength of the second phosphorescent compound,wherein λ
denotes a wavelength, andwherein ε
(λ
) denotes a molar absorption coefficient at the wavelength λ
.
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Abstract
An object is to provide a light-emitting element which uses a plurality of kinds of light-emitting dopants and has high emission efficiency. In one embodiment of the present invention, a light-emitting device, a light-emitting module, a light-emitting display device, an electronic device, and a lighting device each having reduced power consumption by using the above light-emitting element are provided. Attention is paid to Förster mechanism, which is one of mechanisms of intermolecular energy transfer. Efficient energy transfer by Förster mechanism is achieved by making an emission wavelength of a molecule which donates energy overlap with a local maximum peak on the longest wavelength side of a graph obtained by multiplying an absorption spectrum of a molecule which receives energy by a wavelength raised to the fourth power.
57 Citations
28 Claims
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1. A light-emitting element comprising:
-
a first phosphorescent compound; a second phosphorescent compound; and a third phosphorescent compound, wherein the first phosphorescent compound emits blue light, wherein ε
(λ
)λ
4 of the second phosphorescent compound has a peak within a wavelength range of 440 nm to 520 nm,wherein a peak wavelength of the second phosphorescent compound is longer than a peak wavelength of the first phosphorescent compound, wherein ε
(λ
)λ
4 of the third phosphorescent compound has a peak within a wavelength range of 520 nm to 600 nm,wherein a peak wavelength of the third phosphorescent compound is longer than the peak wavelength of the second phosphorescent compound, wherein λ
denotes a wavelength, andwherein ε
(λ
) denotes a molar absorption coefficient at the wavelength λ
. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A light-emitting element comprising:
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a first phosphorescent compound; a second phosphorescent compound; and a third phosphorescent compound, wherein the first phosphorescent compound emits blue light, wherein energy transfer from the first phosphorescent compound to the second phosphorescent compound occurs by utilizing overlap between a photoluminescence spectrum of the first phosphorescent compound and ε
(λ
)λ
4 of the second phosphorescent compound within a wavelength range of 440 nm to 520 nm,wherein a peak wavelength of the second phosphorescent compound is longer than a peak wavelength of the first phosphorescent compound, wherein energy transfer from the second phosphorescent compound to the third phosphorescent compound occurs by utilizing overlap between a photoluminescence spectrum of the second phosphorescent compound and ε
(λ
)λ
4 of the third phosphorescent compound within a wavelength range of 520 nm to 600 nm,wherein a peak wavelength of the third phosphorescent compound is longer than the peak wavelength of the second phosphorescent compound, wherein λ
, denotes a wavelength, andwherein ε
(λ
) denotes a molar absorption coefficient at the wavelength λ
. - View Dependent Claims (9, 10, 11, 12)
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13. A light-emitting element comprising:
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a first electrode; a first light-emitting layer over the first electrode comprising; a first compound; and a first host material; a second light-emitting layer over the first light-emitting layer comprising; a second compound; and a second host material; a third light-emitting layer over the second light-emitting layer comprising; a third compound; and a third host material; and a second electrode over the third light-emitting layer, wherein the first compound emits blue light, wherein ε
(λ
)λ
4 of the second compound has a peak within a wavelength range of 440 nm to 520 nm,wherein a peak wavelength of the second compound is longer than a peak wavelength of the first compound, wherein ε
(λ
)λ
4 of the third compound has a peak within a wavelength range of 520 nm to 600 nm,wherein a peak wavelength the third compound is longer than the peak wavelength of the second compound, wherein λ
denotes a wavelength, andwherein ε
(λ
) denotes a molar absorption coefficient at the wavelength λ
. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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21. A light-emitting element comprising:
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a first electrode; a first light-emitting layer over the first electrode comprising; a first compound; and a first host material; a second light-emitting layer over the first light-emitting layer comprising; a second compound; and a second host material; a third light-emitting layer over the second light-emitting layer comprising; a third compound; and a third host material; and a second electrode over the third light-emitting layer, wherein the first compound emits blue light, wherein a longest-wavelength-side peak of a function ε
(λ
)λ
4 of the second compound overlaps with an emission spectrum F(λ
) of the first compound,wherein a peak wavelength of the second compound is longer than a peak wavelength of the first compound, wherein a longest-wavelength-side peak of a function ε
(λ
)λ
4 of the third compound overlaps with an emission spectrum F(λ
) of the second compound,wherein a peak wavelength the third compound is longer than the peak wavelength of the second compound, wherein λ
denotes a wavelength, andwherein ε
(λ
) denotes a molar absorption coefficient at the wavelength λ
. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28)
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Specification
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Current AssigneeSemiconductor Energy Laboratory Co., Ltd.
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Original AssigneeSemiconductor Energy Laboratory Co., Ltd.
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InventorsYamazaki, Shunpei, Seo, Satoshi, Hirakata, Yoshiharu, Ishisone, Takahiro
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Primary Examiner(s)Jahan, Bilkis
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Application NumberUS14/180,753Publication NumberTime in Patent Office536 DaysField of Search257/59, 257/72US Class Current1/1CPC Class CodesB60Q 3/10 for dashboardsB60Q 3/208 Sun roofs; WindowsC09K 11/06 containing organic luminesc...C09K 2211/1007 Non-condensed systemsC09K 2211/1044 containing two nitrogen ato...C09K 2211/1059 containing three nitrogen a...C09K 2211/185 of the platinum group, i.e....F21S 6/002 Table lamps, e.g. for ambie...F21S 8/04 intended only for mounting ...F21Y 2115/10 Light-emitting diodes [LED]H01L 33/502 Wavelength conversion mater...H01L 33/504 Elements with two or more w...H05B 33/14 characterised by the chemic...H05B 33/145 Arrangements of the electro...H05B 33/20 characterised by the chemic...H10K 2101/10 Triplet emissionH10K 50/11 characterised by the electr...H10K 50/13 comprising stacked EL layer...
