Organic light-emitting device
Provided is an organic light-emitting device exhibiting lower driving voltages and improved lifetime characteristics and emission efficiency. The organic light-emitting device includes a cathode; an anode; and a light-emitting layer interposed between the cathode and the anode, wherein a buffer layer is disposed on at least one surface of the light-emitting layer.
1. An organic light-emitting device comprising: an anode; a hole transport layer; a light-emitting layer; an electron transport layer; a cathode; and at least one of a first buffer layer interposed between the light-emitting layer and the hole transport layer and a second buffer layer interposed between the light-emitting layer and the electron transport layer, wherein the first buffer layer comprises a light-emitting material and a hole transport material, the first buffer layer is formed as a gradient layer of the light emitting material and the hole transport material, and the concentration of the light-emitting material increases towards the light-emitting layer, the concentration of the light-emitting material decreases away from the light-emitting layer, the concentration of the hole transport material increases towards the hole transport layer, and the concentration of the hole transport material decreases away from the hole transport layer; wherein the second buffer layer comprises a light-emitting material and an electron transport material, the second buffer layer is formed as a gradient layer of the light-emitting material and the electron transport material and the concentration of the light-emitting material increases towards the light-emitting layer, the concentration of the light-emitting material decreases away from the light-emitting layer, the concentration of the electron transport material increases towards the electron transport layer, and the concentration of the electron transport material decreases away from the electron transport layer, wherein a mass ratio of the light-emitting material to the hole transport material in the first buffer layer is from 1:9 to 9:1 edge to edge.
2. The organic light-emitting device of claim 1 , wherein the light-emitting material of the first buffer layer is at least one selected from the group consisting of Alq 3 , MADN (2-methyl-9,10-di(2-naphthyl)anthracene), CBP (4,4′-N,N′-dicarbazole-biphenyl), and PVK (poly(n-vinylcarbazole)).
3. The organic light-emitting device of claim 1 , wherein the hole transport material of the first buffer layer is at least one selected from the group consisting of N-phenylcarbazole, polyvinylcarbazole, N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1-bipheny]-4,4′-diamine (TPD), and N,N′-di(naphthalene-1-yl)-N,N′-diphenyl benzidine (α-NPD).
4. The organic light-emitting device of claim 1 , wherein the electron transport material of the second buffer layer is at least one selected from the group consisting of tris(8-quinolinolate)aluminum (Alq 3 ), TAZ, Balq, and Bebq2.
5. The organic light-emitting device of claim 1 , wherein a mass ratio of the light-emitting material and the electron transport material in the second buffer layer is from 1:9 to 9:1.
6. The organic light-emitting device of claim 1 , wherein the light-emitting material of the first buffer layer or the light-emitting material of the second buffer layer is at least one selected from the group consisting of Alq 3 , MADN (2-methyl-9,10-di(2-naphthyl)anthracene), CBP (4,4′-N,N′-dicarbazole-biphenyl), and PVK (poly(n-vinylcarbazole)).
7. The organic light-emitting device of claim 1 , wherein each of the first buffer layer and the second buffer layer has a thickness of 50 to 1,000 Å.
8. The organic light-emitting device of claim 1 , wherein each of the first buffer layer and the second buffer layer is formed by deposition, spin coating, casting, inkjet printing or transfer.
9. The organic light-emitting device of claim 1 , wherein the light-emitting layer is a red light-emitting layer, a blue light-emitting layer, a green light-emitting layer, or a white light-emitting layer.