Light emitting device including semiconductor nanocrystals

• US 10,225,906 B2
• Filed: 10/20/2005
• Issued: 03/05/2019
• Est. Priority Date: 10/22/2004
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Coe-Sullivan, Seth, Steckel, Jonathan S., Kim, LeeAnn, Bawendi, Moungi G., Bulovic, Vladimir
• Primary Examiner(s): Mai, Anh
• Assistant Examiner(s): Farokhrooz, Fatima
• Application Number:
  US11/253,595
• Publication Number:
  US 20080001167A1
• Time in Patent Office: 4,884 Days
• Field of Search: 313498-512
• CPC Class Codes: B41J 2/0057 where an intermediate transfer member receives the ink before transferring it on the printing material
• CPC Class Codes: B41M 1/02 Letterpress printing, e.g. book printing
• CPC Class Codes: B41M 3/003 on optical devices, e.g. lens elements; for the production of optical devices production by thermal imaging means B41M5/265
• CPC Class Codes: B41M 5/0256 the transferable ink pattern being obtained by means of a computer driven printer, e.g. an ink jet or laser printer, or by electrographic means
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: H01L 21/6715 Apparatus for applying a liquid, a resin, an ink or the like H01L21/67126 takes precedence
• CPC Class Codes: H05B 33/10 Apparatus or processes specially adapted to the manufacture of electroluminescent light sources
• CPC Class Codes: H05B 33/145 Arrangements of the electroluminescent material
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/115 comprising active inorganic nanostructures, e.g. luminescent quantum dots
• CPC Class Codes: H10K 71/00 Manufacture or treatment specially adapted for the organic devices covered by this subclass
• CPC Class Codes: H10K 71/20 Changing the shape of the active layer in the devices, e.g. patterning
• CPC Class Codes: H10K 71/40 Thermal treatment, e.g. annealing in the presence of a solvent vapour

Abstract

A light emitting device includes a semiconductor nanocrystal in a layer. The layer can be a monolayer of semiconductor nanocrystals. The monolayer can form a pattern on a substrate.

Claims

1. A method of forming a light emitting device comprising:

modifying a surface of an applicator, wherein modifying the surface of the applicator includes contacting the surface of the applicator with a composition selected to release at least a portion of the plurality of semiconductor nanocrystals from the applicator upon contact with a substrate;

wherein the plurality of semiconductor nanocrystals have no more than a 5% rms deviation from mean diameter, wherein the surface of the applicator includes a pattern,

placing an solvent-free ink including a plurality of semiconductor nanocrystals on the modified surface of the applicator, wherein the plurality of semiconductor nanocrystals forms a monolayer;

contacting the modified surface of the applicator including a solvent-free ink to a substrate including a first electrode, thereby dry-transferring at least a portion of the plurality of semiconductor nanocrystals to the substrate wherein the plurality of semiconductor nanocrystals form a partial monolayer on the substrate;

arranging a second electrode opposed to the first electrode, and the plurality of semiconductor nanocrystals are disposed between the first electrode and the second electrode by contact printing;

placing a second solvent-free ink including a plurality of semiconductor nanocrystals on a surface of a second applicator; and

contacting the surface of the second applicator including a solvent-free second ink to the substrate, thereby dry-transferring at least a portion of the plurality of semiconductor nanocrystals to the substrate wherein the plurality of semiconductor nanocrystals form a partial monolayer on the substrate,

wherein the first plurality of semiconductor nanocrystals have an emission wavelength distinguishable from the second plurality of semiconductor nanocrystals and the first and second pluralities of semiconductor nanocrystals are applied in non-overlapping predefined regions of the substrate and producing a color saturation attributed to a decreased intensity of organic emission and increased intensity of semiconductor nanocrystal emission, leading to a larger ratio between semiconductor nanocrystal electroluminescence to organic electroluminescence.

2. The method of claim 1, wherein the pattern includes an elevation or a depression.

3. The method of claim 1, wherein the plurality of semiconductor nanocrystals forms a pattern on the substrate.

4. The method of claim 1, wherein the composition includes an aromatic organic polymer.

5. The method of claim 1, further comprising placing a third plurality of semiconductor nanocrystals on a surface of a third applicator;

and

contacting the surface of the third applicator to the substrate, thereby transferring at least a portion of the third plurality of semiconductor nanocrystals to the substrate.

6. The method of claim 1, wherein the substrate includes a layer including a hole transport material over the first electrode.

7. The method of claim 1, wherein placing the plurality of semiconductor nanocrystals on the modified surface of the applicator includes spin coating, blade coating, slot coating, dip coating, spray coating, rod coating, reverse roll coating, forward roll coating, air knife coating, knife over roll coating, gravure, microgravure, extrusion coating, slide coating, curtain coating, or a combination thereof.

8. The method of claim 1, wherein the modified surface of the applicator is substantially free of elevations and depressions.

9. The method of claim 2, wherein a feature of the pattern has a dimension of less than 10 millimeters.

10. The method of claim 2, wherein a feature of the pattern has a dimension of less than 1 millimeter.

11. The method of claim 2, wherein a feature of the pattern has a dimension of less than 100 micrometers.

12. The method of claim 2, wherein a feature of the pattern has a dimension of less than 1 micrometer.

13. The method of claim 2, wherein a feature of the pattern has a dimension of at least 1 centimeter.

14. The method of claim 2, wherein a feature of the pattern has a dimension of at least 10 centimeters.

15. The method of claim 2, wherein a feature of the pattern has a dimension of at least 100 centimeters.

16. The method of claim 5, wherein the third plurality of semiconductor nanocrystals have an emission wavelength distinguishable from the first plurality of semiconductor nanocrystals, and distinguishable from the second plurality of semiconductor nanocrystals.

17. The method of claim 16, wherein the first, second and third pluralities of semiconductor nanocrystals are applied in non-overlapping predefined regions of the substrate.

18. The method of claim 17, wherein the emission wavelengths of the first, second and third pluralities of semiconductor nanocrystals are selected from an ultraviolet, blue, green, yellow, red, or infrared emission wavelength, or a combination thereof.

19. The method of claim 6, further comprising forming a layer including an electron transporting material over the plurality of semiconductor nanocrystals.

20. The method of claim 19, wherein the second electrode is applied over the layer including the electron transporting material.

21. The method of claim 8, wherein the applicator is mounted on a rotatable drum, wherein placing the plurality of semiconductor nanocrystals on the surface of the applicator includes intermittent application of the plurality of semiconductor nanocrystals.