Semiconductor nanocrystals, methods for making same, compositions, and products

Patent metadata

Field	Value
Publication number	US-10236410-B2
Application number	US-201414451125-A
Country	US
Kind code	B2
Filing date	Aug 4, 2014
Priority date	Feb 5, 2012
Publication date	Mar 19, 2019
Grant date	Mar 19, 2019

Abstract

A semiconductor nanocrystal 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. is disclosed. A semiconductor nanocrystal having a multiple LO phonon assisted charge thermal escape activation energy of at least 0.5 eV is also disclosed. A semiconductor nanocrystal capable of emitting light with a maximum peak emission at a wavelength in a range from 590 nm to 650 nm characterized by an absorption spectrum, wherein the absorption ratio of OD at 325 nm to OD at 450 nm is greater than 5.5. A semiconductor nanocrystal capable of emitting light with a maximum peak emission at a wavelength in a range from 545 nm to 590 nm characterized by an absorption spectrum, wherein the absorption ratio of OD at 325 nm to OD at 450 nm is greater than 7. A semiconductor nanocrystal capable of emitting light with a maximum peak emission at a wavelength in a range from 495 nm to 545 nm characterized by an absorption spectrum, wherein the absorption ratio of OD at 325 nm to OD at 450 nm is greater than 10. A composition comprising a plurality of semiconductor nanocrystals wherein the solid state photoluminescence efficiency of the composition at a temperature of 90° C. or above is at least 95% of the solid state photoluminescence efficiency of the composition 25° C. is further disclosed. A method for preparing semiconductor nanocrystals comprises introducing one or more first shell chalcogenide precursors and one or more first shell metal precursors to a reaction mixture including semiconductor nanocrystal cores, wherein the first shell chalcogenide precursors are added in an amount greater than the first shell metal precursors by a factor of at least about 2 molar equivalents and reacting the first shell precursors at a first reaction temperature of at least 300° C. to form a first shell on the semiconductor nanocrystal cores. Populations, compositions, components and other products including semiconductor nanocrystals of the invention are disclosed. Populations, compositions, components and other products including semiconductor nanocrystals made in accordance with any method of the invention is also disclosed.

First claim

What is claimed is:

1. A semiconductor nanocrystal 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.; wherein the nanocrystal includes a core comprising a first semiconductor material and a first shell surrounding the core, wherein the first shell comprises a second semiconductor material and is disposed directly on the core,
wherein the nanocrystal further includes a second shell surrounding the outer surface thereof and the second shell comprises a third semiconductor material, where the third semiconductor material comprises a ternary mixture; and
wherein the semiconductor nanocrystal further includes a third shell, wherein the third shell has a bandgap that is the same as that of the first shell and the second shell has a bandgap that is less than that of the first shell.

2. A semiconductor nanocrystal in accordance with claim 1 wherein the temperature is in a range from 90° C. to about 200° C.

3. A semiconductor nanocrystal in accordance with claim 1 wherein the temperature is in a range from 90° C. to about 140° C.

4. A semiconductor nanocrystal in accordance with claim 1 wherein the temperature is in a range from 90° C. to about 120° C.

5. A semiconductor nanocrystal in accordance with claim 1 wherein the solid state photoluminescence efficiency at the temperature of 90° C. or above is from 95 to 100% of the solid state photoluminescence efficiency at 25° C.

6. A semiconductor nanocrystal in accordance with claim 1 wherein the first shell has a thickness greater than or equal to the thickness of 1 monolayer of the second semiconductor material.

7. A semiconductor nanocrystal in accordance with claim 6 wherein the first shell has a thickness up to the thickness of about 10 monolayers of the second semiconductor material.

8. A semiconductor nanocrystal in accordance with claim 1 wherein the second shell has a thickness greater than or equal to the thickness of 3 monolayers of the third semiconductor material.

9. A semiconductor nanocrystal in accordance with claim 8 wherein the second shell has a thickness up to the thickness of about 20 monolayers of the third semiconductor material.

10. A semiconductor nanocrystal in accordance with claim 1 wherein the first shell comprises zinc sulfide, and the second shell comprises one or more metals wherein the one or metals comprises from 0 to less than 100% cadmium.

11. A semiconductor nanocrystal in accordance with claim 1 wherein the core comprises CdSe, the first shell comprises ZnS at a thickness of about 3-4 monolayers of ZnS, and the second shell comprises Cd 1-x Zn x S wherein 0<x<1 at a thickness of about 9-10 monolayers of Cd 1-x Zn x S.

12. A semiconductor nanocrystal in accordance with claim 1 wherein first shell has a bandgap which is greater than that of the second shell.

13. A semiconductor nanocrystal in accordance with claim 1 wherein the first shell has a bandgap which is greater than that of the second shell, and the bandgap of the first shell is also greater than that of the core.

14. A semiconductor nanocrystal in accordance with claim 1 wherein the first semiconductor material has a bandgap which differs from that of the second semiconductor material by at least 0.8 eV.

15. A semiconductor nanocrystal in accordance with claim 1 wherein the first semiconductor material having a first conduction hand energy (E CB ), and the second semiconductor material having a second conduction band energy (E CB ), and wherein the absolute value of the difference between E CB of the core and E CB of the first shell multiplied by the total shell thickness (nm) surrounding the core in the nanocrystal is greater than 2 eV*nm.

16. A semiconductor nanocrystal in accordance with claim 15 wherein the absolute value of the difference between E CB of the core and E CB of the first shell multiplied by the total shell thickness (nm) surrounding the core in the nanocrystal is greater than 4 eV*nm.

17. A semiconductor nanocrystal in accordance with claim 1 wherein the first semiconductor material having a first valence hand energy (E VB ), and the second semiconductor material having a second valence hand energy (E VB ), and wherein the absolute value of the difference between E VB of the core and E VB of the first shell multiplied by the total shell thickness (nm) surrounding the core in the nanocrystal is greater than 2 eV*nm.

18. A semiconductor nanocrystal in accordance with claim 15 wherein the absolute value of the difference between E VB of the core and E VB of the first shell multiplied by the total shell thickness (nm) surrounding the core in the nanocrystal is greater than 4 eV*nm.

19. A semiconductor nanocrystal in accordance with claim 1 wherein the first semiconductor material having a first conduction band energy (E CB ), and the second semiconductor material having a second conduction band energy (E CB ), and wherein the absolute value of the difference between E CB of the core and E CB of the first shell is at least 0.5 eV.

20. A semiconductor nanocrystal in accordance with claim 1 wherein the first semiconductor material having a first valence band energy (E CB ), and the second semiconductor material having a second valence band energy (E CB ), and wherein the absolute value of the difference between E VB of the core and E VB of the first shell is at least 0.5 eV.

21. A light-emitting device comprising a light-emitting element and an optical material arranged to receive and convert at least a portion of light emitted by at least a portion of the light-emitting element from a first emission wavelength to one or more predetermined wavelengths, wherein the material comprises a semiconductor nanocrystal in accordance with claim 1 .

Assignees

• Samsung Electronics Co Ltd

Inventors

• Liu Wenhao
• Breen Craig
• Coe-Sullivan Seth

Classifications

• C09K11/883

  with zinc or cadmium · CPC title

• C09K11/565

  with zinc cadmium · CPC title

• Y10S977/774

  Exhibiting three-dimensional carrier confinement, e.g. quantum dots · CPC title

• C09K11/02 Primary

  Use of particular materials as binders, particle coatings or suspension media therefor · CPC title

• C09D11/52

  Electrically conductive inks · CPC title