ORGANIC EL ELEMENT, METHOD FOR MANUFACTURING THE SAME, ORGANIC EL DISPLAY PANEL, AND ORGANIC EL DISPLAY DEVICE
An organic EL element of the present disclosure is an organic EL element having an inverted structure including a first hole injection layer containing a first organic material whose LUMO level is −4 eV or less. The organic EL element further includes a second hole injection layer containing a second organic material. The second hole injection layer is disposed between the first hole injection layer and an anode. The roughness of a principal surface of the second hole injection layer on the side of the anode is smaller than the roughness of a principal surface of the first hole injection layer on the side of the second hole injection layer. L1, L2, and EA satisfy formula: −EA−2 eV≦L2≦L1+2 eV, where the first organic material has a LUMO level L1, the second organic material has a LUMO level L2, and the anode has an electron affinity EA.
1 . An organic EL element comprising:
a substrate;
a cathode;
an emitting layer;
a first hole injection layer containing a first organic material whose LUMO level is −4 eV or less;
an anode; and
a second hole injection layer containing a second organic material,
wherein the substrate, the cathode, the emitting layer, the first hole injection layer, the second hole injection layer, and the anode are disposed in that order,
a roughness of a principal surface of the second hole injection layer on the side of the anode is smaller than a roughness of a principal surface of the first hole injection layer on the side of the second hole injection layer, and
L1, L2, and EA satisfy formula (1) below,
−EA−2 eV≦ L 2 ≦L 1+2 eV (1)
where the first organic material has a LUMO level L1, the second organic material has a LUMO level L2, and the anode has an electron affinity EA.
2 . The organic EL element according to claim 1 ,
wherein the first organic material is the same as the second organic material,
the second hole injection layer further contains a third organic material having a flatness lower than those of the first organic material and the second organic material, and
a volume ratio of the first organic material in the first hole injection layer is higher than a volume ratio of the second organic material in the second hole injection layer.
3 . The organic EL element according to claim 2 , wherein the third organic material has a hole mobility of 1×10 −2 cm 2 /Vs or less and an electron mobility of 1×10 −2 cm 2 /Vs or less when an electric field of 1×10 4 V/cm or more and 1×10 6 V/cm or less is applied.
4 . The organic EL element according to claim 1 , wherein the first organic material is different from the second organic material.
5 . The organic EL element according to claim 4 , wherein the second organic material has a hole mobility of 1×10 −2 cm 2 /Vs or less and an electron mobility of 1×10 −2 cm 2 /Vs or less when an electric field of 1×10 4 V/cm or more and 1×10 6 V/cm or less is applied.
6 . The organic EL element according to claim 4 ,
wherein the second hole injection layer further contains a third organic material, and
the third organic material has a hole mobility of 1×10 −2 cm 2 /Vs or less and an electron mobility of 1×10 −2 cm 2 /Vs or less when an electric field of 1×10 4 V/cm or more and 1×10 6 V/cm or less is applied.
7 . The organic EL element according to claim 1 , wherein the first organic material is an azatriphenylene derivative represented by chemical formula below,
where R 1 to R 6 in the chemical formula each independently represent a substituent selected from hydrogen, a halogen, a hydroxyl group, an amino group, an arylamino group, a substituted or unsubstituted carbonyl group having 20 or less carbon atoms, a substituted or unsubstituted carbonyl ester group having 20 or less carbon atoms, a substituted or unsubstituted alkyl group having 20 or less carbon atoms, a substituted or unsubstituted alkenyl group having 20 or less carbon atoms, a substituted or unsubstituted alkoxyl group having 20 or less carbon atoms, a substituted or unsubstituted aryl group having 30 or less carbon atoms, a substituted or unsubstituted heterocyclic group having 30 or less carbon atoms, a nitrile group, a cyano group, a nitro group, and a silyl group; adjacent R m (m=1 to 6) may be bonded to each other through a ring structure; and X 1 to X 6 in the chemical formula each independently represent a carbon atom or a nitrogen atom.
8 . The organic EL element according to claim 1 , wherein the first organic material is 1,4,5,8,9,12-hexaazatriphenylene-2,3,6,7,10,11-hexacarbonitrile.
9 . The organic EL element according to claim 2 , wherein the third organic material is N,N′-diphenyl-N,N′-bis(1-naphthyl)benzidine.
10 . The organic EL element according to claim 6 , wherein the third organic material is N,N′-diphenyl-N,N′-bis(1-naphthyl)benzidine.
11 . The organic EL element according to claim 1 , wherein a content of the second organic material in the second hole injection layer is 15 vol % or more.
12 . The organic EL element according to claim 1 , wherein when the first hole injection layer has a, thickness of T nm, the second hole injection layer has a thickness of 0.06×T 2 nm or more.
13 . The organic EL element according to claim 12 , wherein T is 30 or less.
14 . The organic EL element according to claim 2 , wherein a content of the third organic material in the second hole injection layer is 50 vol % or more.
15 . The organic EL element according to claim 6 , wherein a content of the third organic material in the second hole injection layer is 50 vol % or more.
16 . The organic EL element according to claim 1 , further comprising a hole transport layer containing a fourth organic material, the hole transport layer being disposed between the emitting layer and the first hole injection layer,
wherein the fourth organic material has a HOMO level H4, and a difference between L1 and H4 is within 2 eV.
17 . The organic EL element according to claim 2 , further comprising a hole transport layer containing the third organic material, the hole transport layer being disposed between the emitting layer and the first hole injection layer,
wherein the third organic material has a HOMO level H3, and a difference between L1 and H3 is within 2 eV.
18 . The organic EL element according to claim 6 , further comprising a hole transport layer containing the third organic material, the hole transport layer being disposed between the emitting layer and the first hole injection layer,
wherein the third organic material has a HOMO level H3, and a difference between L1 and H3 is within 2 eV.
19 . The organic EL element according to claim 1 , wherein the anode is mainly composed of an alloy of magnesium and silver.
20 . An organic EL display panel comprising the organic EL element according to claim 1 .
21 . An organic EL display device comprising the organic EL display panel according to claim 20 .
22 . A method for manufacturing an organic EL element, comprising:
forming a substrate, a cathode, an emitting layer, a first hole injection layer containing a first organic material whose LUMO level is −4 eV or less, a second, hole injection layer, and an anode in that order,
wherein
L1, L2, and EA satisfy formula (1) below,
−EA−2 eV≦ L 2 ≦L 1+2 eV (1)
where the first organic material has a LUMO level L1, the second organic material has a LUMO level L2, and the anode has an electron affinity EA; and a roughness of a principal surface of the second hole injection layer on the side of the anode is smaller than a roughness of a principal surface of the first hole injection layer on the side of the second hole injection layer.