Light-emitting diode of polymer nanocomposite with quantum dots
The present invention provides a light-emitting diode made of a polymer nanocomposite doped with quantum dots to improve luminescence efficiency and to increase stability and electrical characteristics.
1. A light-emitting diode comprising:
(A) a polymeric nanocomposite of a fluorene copolymer comprising a plurality of side-chain moieties wherein each side-chain moiety (GX) is either bound directly or bound via an ether linkage to the fluorene copolymer and independently selected from the group consisting of:
said polymeric nanocomposite of a copolyfluorene being doped with
(B) quantum dots of a surface-modified cadmium sulfide, wherein the quantum dots are non-luminescent.
2. The light-emitting diode of claim 1 wherein the side-chain moieties are of structure (I).
3. The light-emitting diode of claim 1 wherein the side-chain moieties are of structure (II).
4. The light-emitting diode of claim 1 wherein the side-chain moieties are of structure (III).
5. The light-emitting diode of claim 1 wherein the cadmium sulfide surface is modified by means of a thiophenol surfactant.
6. The light-emitting diode of claim 5 wherein the side-chain moieties are of structure (I).
7. The light-emitting diode of claim 5 wherein the side-chain moieties are of structure (II).
8. The light-emitting diode of claim 5 wherein the side-chain moieties are of structure (III).
9. The light-emitting diode of claim 1 wherein the fluorene copolymer is of the structure:
10. The light-emitting diode of claim 9 wherein the cadmium sulfide surface is modified by means of a thiophenol surfactant.
11. The light-emitting diode of claim 10 wherein the side-chain moieties are of structure (I).
12. The light-emitting diode of claim 10 wherein the side-chain moieties are of structure (II).
13. The light-emitting diode of claim 10 wherein the side-chain moieties are of structure (III).
14. The light-emitting diode of claim 9 wherein the side-chain moieties are of structure (I).
15. The light-emitting diode of claim 9 wherein the side-chain moieties are of structure (II).
16. The light-emitting diode of claim 9 wherein the side-chain moieties are of structure (III).
17. The light-emitting diode of claim 1 wherein the quantum dots of a surface-modified cadmium sulfide are present in a concentration of from about 3 to about 8 percent by weight.
18. A method for preparing the light-emitting diode of claim 1 comprising the steps of:
(A) modifying the surface of the cadmium sulfide by means of a thiophenol surfactant;
(B) copolymerizing a first fluorene monomer with a second fluorene monomer by means of Suzuki coupling; and
(C) processing a blending of the modified cadmium sulfide of step (A) and the product of step (B) by means of a π-π interaction through a physical doping.
19. The method of claim 18 wherein the first fluorene monomer is of the structure:
20. The method of claim 19 wherein the second fluorene monomer is of the structure: