Light-emitting diode and light-emitting device with reduced hole and current leakages

1. A light emitting diode comprising:

an anode;

a cathode positioned to face the anode; and

an emissive layer including an emitting material layer and an electron transfer layer, the emitting material layer is located between the anode and the cathode, and the electron transfer layer is located between the cathode and the emitting material layer;

wherein the electron transfer layer includes:

a first electron transport layer adjacent to the emitting material layer, the first electron transport layer including an organic material; and

a second electron transport layer between the first electron transport layer and the cathode, the second electron transport layer including an inorganic material,

wherein the emitting material layer includes inorganic luminescent particles,

wherein the inorganic luminescent particles include semiconductor nanocrystals, and

wherein a highest occupied molecular orbital (HOMO) energy level of the organic material in the first electron transport layer is higher than a HOMO energy level of the semiconductor nanocrystals,

wherein a valance band energy level of the inorganic material in the second electron transport layer (VB ETL2 ) is lower than a highest occupied molecular orbital (HOMO) energy level of the semiconductor nanocrystals in the emitting material layer (HOMO EML ),

wherein a lowest unoccupied molecular orbital (LUMO) energy level of the first electron transport layer (LUMO ETL1 ) is higher than a LUMO energy level of the emitting material layer (LUMO EML ), and

wherein a lowest unoccupied molecular orbital (LUMO) energy level of the second electron transport layer (LUMO ETL2 ) is higher than a LUMO energy level of the emitting material layer (LUMO EML ).

2. The light emitting diode of claim 1 , wherein the valence band energy level of the inorganic material in the second electron transport layer (VB ETL2 ) and the HOMO energy level of the semiconductor nanocrystals particles in the emitting material layer (HOMO EML ) substantially satisfy the relationship below:

−1.5 eV≤VB ETL2 −HOMO EML ≤−0.7 eV.

3. The light emitting diode of claim 1 , wherein the LUMO energy level of the first electron transport layer (LUMO ETL1 ) and the LUMO energy level of the emitting material layer (LUMO EML ) substantially satisfy the relationship below:

0.5 eV≤LUMO ETL1 −LUMO EML ≤2.8 eV.

4. The light emitting diode of claim 1 , wherein a conduction band energy level of the second electron transport layer (CB ETL2 ) is between a lowest unoccupied molecular orbital (LUMO) of the first electron transport layer (LUMO ETL1 ) and a conduction band energy level of the cathode.

5. The light emitting diode of claim 1 , wherein a highest occupied molecular orbital (HOMO) energy level of the emitting material layer (HOMO EML ) is between a HOMO energy level of the first electron transport layer (HOMO ETL1 ) and a valence band energy level of the second electron transport layer (VB ETL2 ).

6. The light emitting diode of claim 1 , wherein the inorganic material of the second electron transport layer includes metal oxide particles.

7. The light emitting diode of claim 6 , wherein the metal oxide is selected from the group consisting of zinc oxide (ZnO), zinc magnesium oxide (ZnMgO), titanium dioxide (TiO 2 ), zirconium oxide (ZrO 2 ), tin oxide (SnO), tin dioxide (SnO 2 ), tungsten oxide (WO 3 ), tantalum oxide (Ta 2 O 3 ), hafnium oxide (HfO 3 ), aluminum oxide (Al 2 O 3 ), zirconium silicon oxide (ZrSiO 4 ), barium titanium oxide (BaTiO 3 ), barium zirconium oxide (BaZrO 3 ), and combinations thereof.

8. The light emitting diode of claim 1 , wherein the inorganic luminescent particles comprise one or both of quantum dots (QDs) and quantum rods (QRs).

9. The light emitting diode of claim 1 , wherein the semiconductor nanocrystals include group of II-VI semiconductor nanocrystals, group of III-V semiconductor nanocrystals, group IV-VI semiconductor nanocrystals, and group of I-III-V semiconductor nanocrystals.

10. The light emitting diode of claim 1 , wherein the first electron transport layer is disposed between the emitting material layer and the cathode.

11. The light emitting diode of claim 1 , wherein the LUMO energy level of the second electron transport layer (LUMO ETL2 ) is higher than a conduction band energy level of the cathode.

12. The light emitting diode of claim 1 , wherein

the LUMO energy level of the first electron transport layer (LUMO ETL1 ) is higher than the LUMO energy level of the second electron transport layer (LUMO ETL2 ) and

the LUMO energy level of the second electron transport layer (LUMO ETL2 ) is higher than a conduction band energy level of the cathode.

13. A light-emitting device comprising:

a substrate; and

a light emitting diode on the substrate, the light emitting diode including:

an anode;

a cathode positioned to face the anode; and

an emissive layer including an emitting material layer and an electron transfer layer, the emitting material layer is located between the anode and the cathode, and the electron transfer layer is located between the cathode and the emitting material layer;

wherein the electron transfer layer includes:

a first electron transport layer adjacent to the emitting material layer, the first electron transport layer including an organic material; and

a second electron transport layer between the first electron transport layer and the cathode, the second electron transport layer including an inorganic material,

wherein the emitting material layer includes inorganic luminescent particles,

wherein the inorganic luminescent particles include semiconductor nanocrystals, and

wherein a highest occupied molecular orbital (HOMO) energy level of the organic material in the first electron transport layer and a HOMO energy level of the semiconductor nanocrystals are substantially the same, and

wherein a valence band energy level of the inorganic material in the second electron transport layer (VB ETL2 ) is lower than a highest occupied molecular orbital (HOMO) energy level of the semiconductor nanocrystals in in the emitting material layer (HOMO EML ),

wherein a lowest unoccupied molecular orbital (LUMO) energy level of the first electron transport layer (LUMO ETL1 ) is higher than a LUMO energy level of the emitting material layer (LUMO EML ), and

wherein a lowest unoccupied molecular orbital (LUMO) energy level of the second electron transport layer (LUMO ETL2 ) is higher than a LUMO energy level of the emitting material layer (LUMO EML ).

14. The light-emitting device of claim 13 , wherein a conduction band energy level of the second electron transport layer (CB ETL2 ) is between a lowest unoccupied molecular orbital (LUMO) of the first electron transport layer (LUMO ETL1 ) and a conduction band energy level of the cathode.

15. The light-emitting device of claim 13 , wherein a highest occupied molecular orbital (HOMO) energy level of the emitting material layer (HOMO EML ) is between a HOMO energy level of the first electron transport layer (HOMO ETL1 ) and a valence band energy level of the second electron transport layer (VB ETL2 ).

16. The light emitting device of claim 13 , wherein the semiconductor nanocrystals include group of II-VI semiconductor nanocrystals, group of III-V semiconductor nanocrystals, group IV-VI semiconductor nanocrystals, and group of I-III-V semiconductor nanocrystals.

17. The light-emitting device of claim 13 , wherein the valence band energy level of the inorganic material in the second electron transport layer (VB ETL2 ) and the HOMO energy level of the semiconductor nanocrystals in the emitting material layer (HOMO EML ) substantially satisfy the relationship below:

−1.5 eV≤VB ETL2 −HOMO EML ≤−0.7 eV.

18. A light emitting diode comprising:

an anode;

a cathode facing the anode;

an emissive layer including an emitting material layer and an electron transfer layer, the emitting material layer being between the anode and the cathode, and the electron transfer layer being between the cathode and the emitting material layer,

wherein the electron transfer layer includes,

a first electron transport layer adjacent to the emitting material layer, the first electron transport layer including an organic material; and

a second electron transport layer between the first electron transport layer and the cathode, the second electron transport layer including an inorganic material,

wherein the emitting material layer includes one or both of quantum dots (QDs) and quantum rods (QRs),

wherein each of the QDs and the QRs includes a core and a shell surrounding a surface of the core,

wherein each of the core and the shell is made of semiconductor nanocrystals,

wherein a highest occupied molecular orbital (HOMO) energy level of the organic material in the first electron transport layer (HOMO ETL1 ) is higher than a HOMO energy level of the semiconductor nanocrystals of the core or the shell,

wherein a valance band energy level of the inorganic material in the second electron transport layer (VB ETL2 ) is lower than a highest occupied molecular orbital (HOMO) energy level of the core or the shell in the emitting material layer (HOMO EML ),

wherein a lowest unoccupied molecular orbital (LUMO) energy level of the first electron transport layer (LUMO ETL1 ) is higher than a LUMO energy level of the emitting material layer (LUMO EML ), and

wherein a lowest unoccupied molecular orbital (LUMO) energy level of the second electron transport layer (LUMO ETL1 ) is higher than a LUMO energy level of the emitting material layer (LUMO EML ).

19. The light emitting diode of claim 18 , wherein the inorganic material of the second electron transport layer includes metal oxide particles.

20. The light emitting diode of claim 18 , wherein the semiconductor nanocrystals include group of II-VI semiconductor nanocrystals, group of III-V semiconductor nanocrystals, group IV-VI semiconductor nanocrystals, and group of I-III-V semiconductor nanocrystals.

21. The light-emitting diode of claim 18 , wherein the valence band energy level of the inorganic material in the electron transport layer (VB ETL2 ) and the HOMO energy level of the core or the shell in the emitting material layer (HOMO EML ) substantially satisfy the relationship below:

−1.5 eV≤VB ETL2 −HOMO EML ≤−0.7 eV.