LIGHT-EMITTING DEVICE AND ELECTRONIC APPARATUS INCLUDING THE SAME
A light-emitting device and an electronic apparatus including the same. The light-emitting device includes a first electrode, a second electrode facing the first electrode, and an interlayer arranged between the first electrode and the second electrode, the interlayer includes a first emission layer and a second emission layer, the first emission layer includes a first host and a first dopant capable of emitting a first light, the first host includes m1 hosts, m1 is an integer of 1 or more, and when m1 is 2 or more, two or more hosts are present in the first emission layer and are different from the other, the second emission layer includes a second host and a second dopant capable of emitting a second light, the second host includes m2 hosts, m2 is an integer of 1 or more, and when m2 is 2 or more, two or more hosts are present in the second emission layer and are different from the other, the first dopant includes a first transition metal, the second dopant includes a second transition metal different from the first transition metal, and Expression 1 and Expression 2 are satisfied and provided in the present specification.
1 . A light-emitting device comprising:
a first electrode;
a second electrode facing the first electrode; and
an interlayer arranged between the first electrode and the second electrode,
wherein the interlayer comprises a first emission layer and a second emission layer,
the first emission layer comprises a first host and a first dopant capable of emitting a first light having a first photoluminescence spectrum,
the first host comprises m1 hosts, where m1 is an integer of 1 or more, and when m1 is 2 or more, the two or more hosts present in the first emission layer are each different from the other,
the second emission layer comprises a second host and a second dopant capable of emitting a second light having a second photoluminescence spectrum,
the second host comprises m2 hosts, where m2 is an integer of 1 or more, and when m2 is 2 or more, the two or more hosts present in the second emission layer are each different from the other,
the first dopant comprises a first transition metal, and the second dopant comprises a second transition metal,
wherein the first dopant and the second dopant are different from each other, and Expression 1 and Expression 2 are satisfied:
PDM
(
D
1
)
<
PDM
(
D
2
)
Expression
1
PDM
(
H
1
)
>
PDM
(
H
2
)
Expression
2
wherein, in Expressions 1 and 2,
PDM(D1) is a permanent dipole moment of the first dopant and has a unit of debye,
PDM(D2) is a permanent dipole moment of the second dopant and has a unit of debye,
PDM(H1) is ▮ which is a permanent dipole moment average value of the m1 hosts present in the first host, and has a unit of debye, wherein i) x is a variable of 1 to m1, ii) PDM(Hx) is a permanent dipole moment of an x th host in the first emission layer and has a unit of debye, and iii) W(Hx) is a weight fraction of the x th host relative to a total weight of the first host, and is calculated as (a weight of the x th host in the first emission layer/a total weight of the first host),
PDM(H2) is ▮ which is a permanent dipole moment average value of the m2 hosts present in the second host, and has a unit of debye, wherein i) y is a variable of 1 to m2, ii) PDM(Hy) is a permanent dipole moment of an y th host in the second emission layer and has a unit of debye, and iii) W(Hy) is a weight fraction of the y th host relative to a total weight of the second host, and is calculated as (a weight of the y th host in the second emission layer/a total weight of the second host), and
each of PDM(D1), PDM(D2), PDM(Hx), and PDM(Hy) is calculated based on density functional theory (DFT).
2 . The light-emitting device of claim 1 , wherein |PDM(D1)−PDM(D2)| is about 1.0 debye to about 9.0 debye.
3 . The light-emitting device of claim 1 , wherein |PDM(H1)−PDM(H2)| is about 0.01 debye to about 3.99 debye.
4 . The light-emitting device of claim 1 , wherein Expression 3 is further satisfied:
FWHM
(
D
1
)
>
FWHM
(
D
2
)
Expression
3
wherein, in Expression 3,
FWHM(D1) is a full width at half maximum of the first photoluminescence spectrum of the first dopant and has a unit of nanometers,
FWHM(D2) is a full width at half maximum of the second photoluminescence spectrum of the second dopant and has a unit of nanometers,
the first photoluminescence spectrum is evaluated relative to a first film including the first dopant, and
the second photoluminescence spectrum is evaluated relative to a second film including the second dopant.
5 . The light-emitting device of claim 1 , wherein Expression 4 is further satisfied:
D
st
(
D
1
)
<
D
st
(
D
2
)
Expression
4
wherein, in Expression 4,
D st (D1) is |S 1 (D1)−T 1 (D1)|,
D st (D2) is |S 1 (D2)−T 1 (D2)|,
S 1 (D1) is singlet energy of the first dopant and has a unit of eV,
T 1 (D1) is triplet energy of the first dopant and has a unit of eV,
S 1 (D2) is singlet energy of the second dopant and has a unit of eV,
T 1 (D2) is triplet energy of the second dopant and has a unit of eV, and
each of S 1 (D1), T 1 (D1), S 1 (D2), and T 1 (D2) is calculated based on DFT.
6 . The light-emitting device of claim 1 , wherein |λmax(1)−λmax(2)| is 0 nm to about 30 nm,
λmax(1) is a maximum emission peak wavelength of the first photoluminescence spectrum and has a unit of nanometers, and
λmax(2) is a maximum emission peak wavelength of the second photoluminescence spectrum and has a unit of nanometers.
7 . The light-emitting device of claim 1 , wherein
i) each of λmax(1) and λmax(2) is about 510 nm to about 540 nm; or
ii) each of λmax(1) and λmax(2) is about 540 nm to about 570 nm,
λmax(1) is a maximum emission peak wavelength of the first photoluminescence spectrum and has a unit of nm, and
λmax(2) is a maximum emission peak wavelength of the second photoluminescence spectrum and has a unit of nm.
8 . The light-emitting device of claim 1 , wherein
i) λmax(1) is about 510 nm to about 540 nm, and λmax(2) is about 540 nm to about 570 nm; or
ii) λmax(1) is about 540 nm to about 570 nm, and λmax(2) is about 510 nm to about 540 nm,
λmax(1) is a maximum emission peak wavelength of the first photoluminescence spectrum and has a unit of nm, and
λmax(2) is a maximum emission peak wavelength of the second photoluminescence spectrum and has a unit of nm.
9 . The light-emitting device of claim 1 , wherein the first light and the second light is green light.
10 . The light-emitting device of claim 1 , wherein the first emission layer and the second emission layer emit green light.
11 . The light-emitting device of claim 1 , wherein a surface of the first emission layer and a surface of the second emission layer are in direct contact.
12 . The light-emitting device of claim 1 , wherein the first emission layer is arranged between the second emission layer and the second electrode.
13 . The light-emitting device of claim 1 , wherein the second emission layer is arranged between the first emission layer and the second electrode.
14 . The light-emitting device of claim 1 , wherein the first transition metal is platinum, and the second transition metal is iridium.
15 . The light-emitting device of claim 1 , wherein the interlayer comprises:
m light-emitting units, each comprising at least one emission layer; and
m−1 charge generation layers arranged between two adjacent light-emitting units among the m light-emitting units,
m is an integer of 2 or more,
i) a first light-emitting unit among the m light-emitting units comprises the first emission layer, and a second light-emitting unit among the m light-emitting units comprises the second emission layer, or
ii) one light-emitting unit among the m light-emitting units comprises both the first emission layer and the second emission layer.
16 . The light-emitting device of claim 15 , wherein one light-emitting unit among the m light-emitting units comprises both the first emission layer and the second emission layer, and
the one light-emitting unit comprising both the first emission layer and the second emission layer emits green light.
17 . The light-emitting device of claim 16 , wherein the first emission layer is arranged between the second emission layer and the second electrode.
18 . The light-emitting device of claim 16 , wherein the second emission layer is arranged between the first emission layer and the second electrode.
19 . The light-emitting device of claim 15 , wherein at least one light-emitting unit among the m light-emitting units emits blue light.
20 . An electronic apparatus comprising the light-emitting device of claim 1 .