White organic light-emitting device and display device using the same
A white organic light-emitting device including a first electrode, a second electrode, the second electrode and the first electrode facing each other, a blue light-emitting stack, a phosphorescent light-emitting stack including a hole transport layer, an electron transport layer, a red light-emitting layer, and a green light-emitting layer that includes a hole-transporting host, an electron-transporting host, a first dopant having a green emission peak, and a non-emissive second dopant, where the blue light-emitting stack and the phosphorescent light-emitting stack are between the first electrode and the second electrode, and a charge generation layer interposed between the blue light-emitting stack and the phosphorescent light-emitting stack.
1 . A white organic light-emitting device, comprising:
a first electrode;
a second electrode, the second electrode and the first electrode facing each other;
a blue light-emitting stack;
a phosphorescent light-emitting stack comprising
a hole transport layer;
a red light-emitting layer on the hole transport layer;
a green light-emitting layer on the red light-emitting layer, the green light-emitting layer comprising
a hole-transporting host;
an electron-transporting host;
a first dopant having a green emission peak; and
a non-emissive second dopant; and
an electron transport layer on the green light-emitting layer;
wherein the blue light-emitting stack and the phosphorescent light-emitting stack are between the first electrode and the second electrode; and
a charge generation layer between the blue light-emitting stack and the phosphorescent light-emitting stack,
wherein a highest occupied molecular orbital, HOMO, energy level of the second dopant is lower than a HOMO energy level of the electron-transporting host, and
wherein a lowest unoccupied molecular orbital, LUMO, energy level of the second dopant is higher than a LUMO energy level of the first dopant.
2 . The white organic light-emitting device according to claim 1 , wherein a difference, ΔEst, between a singlet energy level of the second dopant and a triplet energy level of the second dopant is 0.6 eV or more.
3 . The white organic light-emitting device according to claim 1 , wherein a singlet energy level of the second dopant is greater than a singlet energy level of each of the hole-transporting host, the electron-transporting host, and the first dopant, and
wherein the singlet energy level of each of the hole-transporting host and the electron-transporting host is 2.7 eV or more.
4 . The white organic light-emitting device according to claim 3 , wherein a triplet energy level of the second dopant is less than a triplet energy level of each of the hole-transporting host and the electron-transporting host, and is greater than a triplet energy level of the first dopant, and
wherein the triplet energy level of the first dopant is 2.4 eV or more.
5 . The white organic light-emitting device according to claim 1 , wherein the second dopant has a photoluminescence peak at a wavelength of 400 nm or less.
6 . The white organic light-emitting device according to claim 1 , wherein the second dopant has an energy band gap of 3 eV or more and a HOMO energy level of −6.0 eV or less.
7 . The white organic light-emitting device according to claim 1 , wherein an electron mobility of the second dopant is higher than a hole mobility of the second dopant.
8 . The white organic light-emitting device according to claim 1 , wherein the first dopant and the second dopant are present in the green light-emitting layer in a total amount of from 0.02 vol % to 30 vol %, based on a total volume of the hole-transporting host and the electron-transporting host, and
wherein the second dopant is present in the green light-emitting layer in an amount of from 0.01 vol % to 20 vol %, based on the total volume of the hole-transporting host and the electron-transporting host.
9 . The white organic light-emitting device according to claim 1 , wherein the blue light-emitting stack includes a first blue light-emitting stack and a second blue light-emitting stack between the first electrode and the second electrode.
10 . The white organic light-emitting device according to claim 9 , wherein the first and second blue light-emitting stacks are disposed adjacent to the first electrode or the second electrode, or
wherein the phosphorescent light-emitting stack is disposed between the first blue light-emitting stack and the second blue light-emitting stack, a first charge generation layer is between the phosphorescent light-emitting stack and the first blue light-emitting stack, and a second charge generation layer is between the phosphorescent light-emitting stack and the second blue light-emitting stack.
11 . The white organic light-emitting device according to claim 1 , wherein the red light-emitting layer has an emission peak at a wavelength of from 600 nm to 640 nm, and
wherein the green light-emitting layer has an emission peak at a wavelength of from 500 nm to 540 nm.
12 . The white organic light-emitting device according to claim 1 , wherein the red light-emitting layer has an emission peak at a wavelength of from 600 nm to 640 nm, and
wherein the green light-emitting layer has an emission peak at a wavelength of from 540 nm to 580 nm.
13 . A display device, comprising:
a substrate comprising a thin-film transistor at each of sub-pixels;
a first electrode connected to the thin-film transistor at each of the sub-pixels;
a second electrode over the sub-pixels and spaced apart from the first electrode;
a blue light-emitting stack;
a phosphorescent light-emitting stack comprising
a hole transport layer;
a red light-emitting layer on the hole transport layer; and
a green light-emitting layer on the red light-emitting layer, the green light-emitting layer comprising
a hole-transporting host;
an electron-transporting host;
a first dopant having a green emission peak; and
a non-emissive second dopant; and
an electron transport layer on the green light-emitting layer;
wherein the blue light-emitting stack and the phosphorescent light-emitting stack are between the first electrode and the second electrode; and
a charge generation layer between the blue light-emitting stack and the phosphorescent light-emitting stack,
wherein a highest occupied molecular orbital, HOMO, energy level of the second dopant is lower than a HOMO energy level of the electron-transporting host, and
wherein a lowest unoccupied molecular orbital, LUMO, energy level of the second dopant is higher than a LUMO energy level of the first dopant.
14 . The display device according to claim 13 , wherein a difference, ΔEst, between a singlet energy level of the second dopant and a triplet energy level of the second dopant is 0.6 eV or more.
15 . The display device according to claim 13 , wherein a singlet energy level of the second dopant is greater than a singlet energy level of each of the hole-transporting host, the electron-transporting host, and the first dopant, and
wherein the singlet energy level of each of the hole-transporting host and the electron-transporting host is 2.7 eV or more.
16 . The display device according to claim 13 , wherein a triplet energy level of the second dopant is less than a triplet energy level of each of the hole-transporting host and the electron-transporting host, and is greater than a triplet energy level of the first dopant, and
wherein the triplet energy level of the first dopant is 2.4 eV or more.
17 . The display device according to claim 13 , wherein the second dopant has a photoluminescence peak at a wavelength of 400 nm or less.
18 . The display device according to claim 13 , wherein the second dopant has an energy band gap of 3 eV or more and a HOMO energy level of −6.0 eV or less.