Organic light-emitting diode and display panel
Provided is an organic light-emitting diode. The organic light-emitting diode includes a first electrode, a second electrode, a light-emitting layer and a hole blocking layer, where the first electrode and the second electrode are oppositely disposed; the light-emitting layer is disposed between the first electrode and the second electrode; the hole blocking layer is disposed between the light-emitting layer and the second electrode; and the hole blocking layer includes at least two hole blocking sub-layers which are stacked, where a lowest unoccupied molecular orbital (LUMO) energy level decreases sequentially in the at least two hole blocking sub-layers.
1. An organic light-emitting diode, comprising:
a first electrode and a second electrode disposed oppositely with each other;
a light-emitting layer disposed between the first electrode and the second electrode; and
a hole blocking layer disposed between the light-emitting layer and the second electrode;
wherein the hole blocking layer comprises at least two hole blocking sub-layers which are stacked, and a lowest unoccupied molecular orbital (LUMO) energy level decreases sequentially in the at least two hole blocking sub-layers;
wherein an energy level difference L 1 between the LUMO energy level of two adjacent hole blocking sub layers among the at least two hole blacking sub layers satisfies: L 1 ≤0:15 eV;
and wherein
along a direction from the light-emitting layer to the second electrode, the LUMO energy level decreases sequentially in the at least two hole blocking sub-layers, a highest occupied molecular orbital (HOMO) energy level decreases sequentially in the at least two hole blocking sub-laver, and the LUMO energy level of each of the at least two hole blocking sub-layers is lower than a LUMO energy level of the light-emitting layer, wherein the LUMO energy level of each of the at least two hole blocking sub-layers is higher than a Fenn energy level of the second electrode, a HOMO energy level of the light-emitting layer is lower than a Fermi energy level of the first electrode and a HOMO energy level of each of the at least two hole blocking sub-layers is lower than the HOMO energy level of the light-emitting layer: or
along a direction from the second electrode to the light-emitting layer, the LUMO energy level decreases sequentially in the at least two hole blocking sub-layers, a HOMO energy level decreases sequentially in the at least two hole blocking sub-layers, and the LUMO energy level of each of the at least two hole blocking sub-layers is lower than a LUMO energy level of the light-emitting layer, wherein a LUMO energy level of at least one of the at least two hole blocking sub-layers is higher than a Fermi energy level of the second electrode, a HOMO energy level of each of the al: least two hole blocking sub-layers is lower than HOMO energy level of the light-emitting layer, and the HOMO energy level of the light-emitting layer is lower than a Fermi energy level of the first electrode.
2. The organic light-emitting diode of claim 1 , wherein the energy level difference L 1 between the LUMO energy level of the two adjacent hole blocking sub-layers among the at least two hole blocking sub-layers satisfies: L 1 ≤0.1 eV.
3. The organic light-emitting diode of claim 1 , wherein an energy level difference L 2 between the LUMO energy level of the light-emitting layer and the LUMO energy level of one hole blocking sub-layer with a highest LUMO energy level among the at least two hole blocking sub-layers satisfies: L 2 ≤0.1 eV; and the hole blocking sub-layer with the highest LUMO energy level has the LUMO energy level closest to the LUMO energy level of the light-emitting layer.
4. The organic light-emitting diode of claim 3 , wherein the energy level difference L 2 between the LUMO energy level of the light-emitting layer and the LUMO energy level of the hole blocking sub-layer with the highest LUMO energy level among the at least two hole blocking sub-layers satisfies: L 2 ≤0.08 eV.
5. The organic light-emitting diode of claim 1 , wherein in the hole blocking layer, an energy level difference H 1 between a highest occupied molecular orbital (HOMO) energy level of at least one of the at least two hole blocking sub-layers and a HOMO energy level of the light-emitting layer has a value range: 0.2 eV≤H 1 ≤0.5 eV.
6. The organic light-emitting diode of claim 5 , wherein in the hole blocking layer, the energy level difference H 1 between the HOMO energy level of the at least one of the at least two hole blocking sub-layers and the HOMO energy level of the light-emitting layer has a value range: 0.3 eV≤H 1 ≤0.4 eV.
7. The organic light-emitting diode of claim 1 , wherein a thickness T 1 of each of the at least two hole blocking sub-layers has a value range: 0 nm<T 1 ≤5 nm.
8. The organic light-emitting diode of claim 7 , wherein the thickness T 1 of each of the at least two hole blocking sub-layers has a value range: 0 nm<T 1 ≤3.5 nm.
9. The organic light-emitting diode of claim 4 , wherein a thickness T 2 of one of the at least two hole blocking sub-layers which abuts against the light-emitting layer has a value range: 2.3 nm≤T 2 ≤2.8 nm.
10. The organic light-emitting diode of claim 9 , wherein the thickness T 2 of the one of the at least two hole blocking sub-layers which abuts against the light-emitting layer has a value range: 2.3 nm≤T 2 ≤2.8 nm.
11. The organic light-emitting diode of claim 1 , further comprising a first carrier functional layer and a second carrier functional layer; wherein the first carrier functional layer is disposed between the first electrode and the light-emitting layer; and the second carrier functional layer is disposed between the hole blocking layer and the second electrode.
12. A display panel, comprising a substrate and a plurality of pixel units disposed on a side of the substrate and arranged in an array; wherein each of the plurality of pixel units comprises the organic light-emitting diode of claim 1 .
13. The organic light-emitting diode of claim 11 , wherein the first carrier functional layer 15 is a hole-type auxiliary functional layer, and the first carrier functional layer have a multilayer structure including a hole injection layer, a hole transport layer and an electron blocking layer, and the second carrier function layer includes an electron injection layer and an electron transport layer.
14. The organic light-emitting diode of claim 13 , wherein along a direction from the second electrode to the light-emitting layer, the LUMO energy level decreases sequentially in the at least two hole blocking sub-layers, the LUMO energy level of each of the at least two hole blocking sub-layers is lower than a LUMO energy level of the light-emitting layer and the LUMO energy level of each of the at least two hole blocking sub-layers is higher than a LUMO energy level of the electron transport layer; and
along the direction from the second electrode to the light-emitting layer, a LUMO energy level of the electron blocking layer, the LUMO energy level of the light-emitting layer, the LUMO energy level of the electron transport layer, a LUMO energy level of the electron injection layer, a Fermi energy level of the second electrode decrease sequentially.
15. The organic light-emitting diode of claim 13 , wherein along a direction from the second electrode to the light-emitting layer, the HOMO energy level decreases sequentially in the at least two hole blocking sub-layers, and the HOMO energy level of each of the at least two hole blocking sub-layers is lower than a HOMO energy level of the light-emitting layer; and along a direction from the second electrode to the light-emitting layer, a Fermi energy level of the first electrode, a HOMO energy level of the hole injection layer, a HOMO energy level of the hole transport layer, a HOMO energy level of the electron blocking layer the HOMO energy level of the light-emitting layer decrease sequentially.