Coated semiconductor nanocrystals and products including same
A coated quantum dot is provided wherein the quantum dot is characterized by having a solid state photoluminescence external quantum efficiency at a temperature of 90° C. or above that is at least 95% of the solid state photoluminescence external quantum efficiency of the semiconductor nanocrystal at 25° C. Products including quantum dots described herein are also disclosed.
1. A quantum dot comprising:
a core quantum dot comprising a Group II-VI semiconductor material, an alloy thereof, or a mixture thereof;
a first semiconductor shell consisting of ZnS or ZnSe; and
a second semiconductor shell comprising a second semiconductor material over the first semiconductor shell, wherein the second semiconductor material is different from the first semiconductor shell,
the second semiconductor material comprises a ternary or quaternary alloy of a Group II-VI compound, and wherein the core quantum dot comprises MX wherein M is cadmium, zinc, or a mixture thereof and X is sulfur, selenium, tellurium, or a combination thereof.
2. The quantum dot of claim 1 , wherein the quantum dot comprises a third shell comprising a third semiconductor material, wherein the third shell has a bandgap that is the same as or greater than that of the first shell.
3. The quantum dot of claim 1 , wherein the core quantum dot comprises zinc.
4. The quantum dot of claim 1 , wherein the core quantum dot comprises ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, or a mixture or an alloy thereof, and the second semiconductor material comprises zinc and sulfur.
5. The quantum dot of claim 1 wherein the first shell has a bandgap that is greater than that of the core quantum dot.
6. The quantum dot of claim 1 , wherein the first shell consists of ZnSe and the second shell comprises zinc and sulfur.
7. The quantum dot of claim 1 wherein the first semiconductor shell has a thickness from about 1 to about 20 monolayers.
8. The quantum dot of claim 1 wherein the second semiconductor shell has a thickness from about 1 to about 25 monolayers.
9. Quantum dots comprising a quantum dot core with a first coating consisting of a zinc chalcogenide on an outer surface of the quantum dot core and a second coating comprising a second semiconductor material and disposed over the first coating,
wherein the quantum dot core comprises a Group II-VI semiconductor material, an alloy thereof, or a mixture thereof;
wherein the zinc chalcogenide is ZnS or ZnSe,
wherein the second semiconductor material is different from the zinc chalcogenide of the first coating, and
the second semiconductor material comprises a ternary or quaternary alloy of a Group II-VI compound, and wherein the quantum dot core comprises MX wherein M is cadmium, zinc, or a mixture thereof and X is sulfur, selenium, tellurium, or a combination thereof.
10. The quantum dots of claim 9 , wherein the quantum dot core comprises zinc.
11. The quantum dots of claim 9 , wherein the quantum dot core comprises ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, or a mixture or an alloy thereof, and the second semiconductor material comprises zinc and sulfur.
12. The quantum dots of claim 9 , wherein the quantum dot core comprises a material different from the first coating.
13. The quantum dots of claim 9 , wherein the first coating has a bandgap that is greater than that of the quantum dot core.
14. The quantum dots of claim 9 , wherein the first coating consists of ZnSe and the second semiconductor material comprises zinc and sulfur.
15. The quantum dots of claim 9 , wherein the quantum dots has no more than 15% rms deviation from mean diameter.
16. The quantum dots of claim 9 , wherein the quantum dots has no more than 10% rms deviation from mean diameter.
17. The quantum dots of claim 9 , wherein the quantum dots has a full width half maximum (FWHM) of emission peak within a range of less than or equal to about 40 nm.
18. A ink comprising the quantum dots of claim 9 and a liquid vehicle, wherein the liquid vehicle comprises an organic solvent and the quantum dots are configured to be dispersed in the organic solvent.
19. The ink of claim 17 , wherein the liquid vehicle comprises a composition including one or more functional groups or units that are capable of being cross-linked.
20. An electronic device comprising the quantum dots of claim 9 .
21. The quantum dot of claim 9 , wherein the quantum dot comprises a third coating comprising a third semiconductor material, wherein the third coating has a bandgap that is the same as or greater than that of the first coating.