Metal halide solid-state surface treatment for nanocrystal materials

1. A method of treating a quantum dot material, comprising:

contacting a first layer of quantum dots with a solution comprising metal ions and halogen ions dissolved in a polar aprotic solvent, wherein the ions in the solution displace native ligands from the quantum dots.

2. The method of claim 1 , further comprising:

depositing a second layer of quantum dots on the first layer; and

contacting the second layer with a ligand solution.

3. The method of claim 1 , wherein the metal ions and the halogen ions are provided by at least one metal halide.

4. The method of claim 3 , wherein the metal halide comprises at least one of PbCl 2 , PbI 2 , CdCl 2 , or CdI 2 .

5. The method of claim 1 , wherein the polar aprotic solvent is dimethylformamide.

6. The method of claim 1 , wherein the contacting is performed at about room temperature in an oxygen containing environment.

7. The method of claim 1 , wherein the quantum dots comprise at least one of PbS or PbSe.

8. The method of claim 1 , further comprising:

depositing a second layer of quantum dots on the first layer;

contacting the second layer with the solution;

depositing a third layer of quantum dots on the second layer; and

contacting the third layer of quantum dots with a ligand solution.

9. A method of making a quantum dot device, comprising:

depositing a first plurality of layers of quantum dots on a substrate, wherein each deposited layer in the first plurality of layers is contacted with a solution comprising metal ions and halogen ions before deposition of the next layer; and

depositing a second plurality of layers of quantum dots on the first plurality of layers, wherein each deposited layer in the second plurality of layers of quantum dots is contacted with a ligand solution.

10. The method of claim 9 , wherein the solution comprises dimethylformamide.

11. The method of claim 10 , further comprising:

contacting each deposited layer in the first plurality of layers with an acetonitrile solution to remove residual dimethylformamide before deposition of the next layer.

12. The method of claim 9 , wherein the contacting each layer of the first plurality of layers comprises immersing each layer of the first plurality of layers in the solution for about 1 second to about 60 seconds.

13. The method of claim 9 , wherein the metal ions and the halogen ions are provided by a metal halide and the solution comprises a concentration of about 10 mM of the metal halide.

14. The method of claim 9 , wherein the ligand solution comprises mercaptopropionic acid and the ligand solution comprises about 10% mercaptopropionic acid and about 90% methanol.

15. The method of claim 13 , wherein the metal halide comprises at least one of PbCl 2 , PbI 2 , CdCl 2 , or CdI 2 .

16. The method of claim 9 , wherein the first plurality of layers and the second plurality of layers have a combined thickness of 300 nm to 750 nm.

17. The method of claim 16 , wherein the combined thickness is about 500 nm.

18. The method of claim 9 , wherein depositing the first plurality of layers comprises:

depositing a first layer of quantum dots on the substrate;

contacting the first layer with the solution;

depositing a second layer of quantum dots on the first layer;

contacting the second layer with the solution; and

depositing one or more additional layers to create the plurality of layers, each deposited layer being contacted with the solution before deposition of a next layer.

19. The method of claim 18 , wherein the first layer, the second layer, and the one or more additional layers are deposited by dip coating or spin coating.

20. The method of claim 9 , wherein the first plurality of layers comprises 10 to 15 layers of quantum dots.