Organic light-emitting diode containing co-hosts forming exciplex, and lighting device and display apparatus including same
Provided are an organic light-emitting diode (“OLED”) including a bottom electrode, a top electrode disposed opposite to the bottom electrode, and an organic layer that is interposed between the bottom electrode and the top electrode and includes a hole-transporting host and an electron-transporting host forming an exciplex and a phosphorescent dopant having a triplet energy which is lower than the triplet energy of the hole-transporting host, the triplet energy of the electron-transporting host, and the triplet energy of the exciplex, and a lighting device and a display apparatus including the OLED. Instead of a phosphorescent dopant, the fluorescent dopant having a singlet energy which is lower than the singlet energy of the exciplex may be also used.
1. An organic light-emitting diode (OLED) comprising:
a bottom electrode;
a top electrode disposed oppositely to the bottom electrode; and
an organic layer that is disposed between the bottom electrode and the top electrode and comprises a hole-transporting host and an electron-transporting host, and a fluorescent dopant,
wherein the hole-transporting host and the electron-transporting host form an exciplex, where the exciplex has less than 0.3 eV of an energy difference between a singlet energy and a triplet energy of the exciplex, and the fluorescent dopant has a singlet energy which is lower than the singlet energy of the exciplex; wherein the hole-transporting host and the electron-transporting host are mixed in a combination selected from TCTA:B3PYMPM, TCTA:3TPYMB, TCTA:BSFM,CBP:B3PYMPM, and NPB:BSFM.
2. The OLED of claim 1 , wherein the hole-transporting host and the electron-transporting host satisfy the following relational expressions 1 and 2:
LUMO energy of the hole-transporting host—LUMO energy of the electron-transporting host >0.2 eV and (1)
HOMO energy of the hole-transporting host—HOMO energy of the electron-transporting host >0.2 eV. (2 )
3. The OLED of claim 1 , wherein the organic layer comprises a light emitting layer.
4. The OLED of claim 1 , wherein the organic layer comprises a light emitting layer, a hole transport layer disposed between the light emitting layer and the bottom electrode, and an electron transport layer disposed between the light emitting layer and the top electrode,
wherein the hole-transporting host, the electron-transporting host and the fluorescent dopant are included in the light emitting layer.
5. The OLED of claim 4 , wherein the hole transport layer comprises a hole-transporting material that is the same as the hole-transporting host, and the electron transport layer comprises an electron-transporting material that is the same as the electron-transporting host.
6. The OLED of claim 1 , wherein λ max of photoluminescence of the exciplex is about 450 nm or less.
7. The OLED of claim 6 , wherein the hole-transporting host and the electron-transporting host are mixed in a combination selected from TCTA:3TPYMB, and CBP:B3PYMPM.
8. A lighting device comprising the OLED according to claim 1 .
9. A display apparatus comprising the OLED according to claim 1 .