Electronic and optoelectronic devices with quantum dot films
Optical and optoelectronic devices and methods of making same. Under one aspect, an optical device includes an integrated circuit an array of conductive regions; and an optically sensitive material over at least a portion of the integrated circuit and in electrical communication with at least one conductive region of the array of conductive regions. Under another aspect, a method of forming a nanocrystalline film includes fabricating a plurality of nanocrystals having a plurality of first ligands attached to their outer surfaces; exchanging the first ligands for second ligands of different chemical composition than the first ligands; forming a film of the ligand-exchanged nanocrystals; removing the second ligands; and fusing the cores of adjacent nanocrystals in the film to form an electrical network of fused nanocrystals. Under another aspect, a film includes a network of fused nanocrystals, the nanocrystals having a core and an outer surface, wherein the core of at least a portion of the fused nanocrystals is in direct physical contact and electrical communication with the core of at least one adjacent fused nanocrystal, and wherein the film has substantially no defect states in the regions where the cores of the nanocrystals are fused.
1. A film comprising a network of fused nanocrystals, the nanocrystals having a core and an outer surface, wherein the core of at least a portion of the fused nanocrystals is in direct physical contact and electrical communication with the core of at least one adjacent fused nanocrystal, the outer surface including a semiconductor material, the film having substantially no defect states in the regions where the cores of the nanocrystals are fused.
2. The film of claim 1 , wherein the outer surface includes at least one defect state.
3. The film of claim 1 , wherein the film is substantially inorganic.
4. The film of claim 1 , wherein the film is substantially free of ligands on the outer surfaces of the fused nanocrystals.
5. The film of claim 1 , wherein the network of fused nanocrystals defines a conductive electrical network.
6. The film of claim 1 , wherein the network of fused nanocrystals has an electrical resistance of at least about 25 k-Ohm/square.
7. The film of claim 1 , wherein the network of fused nanocrystals has a carrier mobility of between about 0.001 and about 10 cm 2 /Vs.
8. The film of claim 1 , wherein the network of fused nanocrystals has a carrier mobility of between about 0.01 and about 0.1 cm 2 /Vs.
9. The film of claim 1 , wherein the network of fused nanocrystals is optically sensitive.
10. The film of claim 1 , wherein the network of fused nanocrystals has a substantially linear responsivity to irradiation in at least a portion of the electromagnetic spectrum.
11. The film of claim 1 , wherein the film is disposed on a substrate.
12. The film of claim 11 , wherein the substrate is flexible and formed in a non-planar shape.
13. The film of claim 11 , wherein the substrate comprises an integrated circuit, at least some components of which are in electrical communication with the film.
14. The film of claim 11 , wherein the substrate comprises at least one of a semiconducting organic molecule, a semiconducting polymer, and a crystalline semiconductor.
15. The film of claim 11 , wherein the film has an electrical resistance of at least about 25 k-Ohm/square.
16. The film of claim 1 , wherein the network of fused nanocrystals includes fused nanocrystals of different compositions.
17. The film of claim 1 , wherein the network of fused nanocrystals includes fused nanocrystals of different sizes.
18. The film of claim 1 , wherein the fused nanocrystals comprise at least one of PbS, InAs, InP, PbSe, CdS, CdSe, In x Ga 1-x As, (Cd-Hg)Te, ZnSe(PbS), ZnS(CdSe), ZnSe(CdS), PbO(PbS), and PbSO 4 (PbS).
19. The film of claim 1 ,wherein the film has an optical response to irradiation in at least one of the infrared, ultraviolet, x-ray, and visible regions of the electromagnetic spectrum.
20. The film of claim 19 , wherein the optical response of the film is related to a size of the fused nanocrystals in the film.
21. The film of claim 19 , wherein the fused nanocrystals have individual properties that vary by less than about 10% from the individual properties of unfused nanocrystals having the same size, shape, and composition as the fused nanocrystals.
22. A device, comprising:
(a) a film comprising a network of fused nanocrystals, the nanocrystals having a core and an outer surface, wherein the core of at least a portion of the fused nanocrystals is in direct physical contact and electrical communication with the core of at least one adjacent fused nanocrystal, the outer surface comprising a semiconductor material, the film having substantially no defect states in the regions where the cores of the nanocrystals are fused; and
(b) first and second electrodes in spaced relation and in electrical communication with first and second portions of the network of fused nanocrystals.
23. The device of claim 22 , wherein the film is substantially free of ligands attached to the outer surface of the fused nanocrystals.
24. The device of claim 23 , wherein the outer surfaces include at least one defect state.
25. The device of claim 24 , wherein the at least one defect state comprises at least one trap state for a hole during operation of the optical device.
26. The device of claim 22 , wherein the electrical network of fused nanocrystals provides a plurality of relatively low-resistance electrical paths from the first electrode to the second electrode.
27. The device of claim 26 , wherein the film has an electrical resistance of at least about 25 k-Ohm/square.
28. The device of claim 26 , wherein the electrical resistance of the film changes in response to irradiation by light.
29. The device of claim 22 , wherein the electrical network of fused nanocrystals provides a plurality of electrical paths from the first electrode to the second electrode and wherein at least some of those electrical paths undergo a change in electrical resistance in response to incident light.
30. The device of claim 22 , wherein the film has a carrier mobility of between about 0.001 cm 2 /Vs and about 10 cm 2 /Vs.
31. The device of claim 22 , wherein the film has a carrier mobility of between about 0.01 cm 2 /Vs and about 0.1 cm 2 /Vs.
32. The device of claim 22 , wherein the fused nanocrystals comprise a plurality of a first type of fused nanocrystals and a plurality of a second type of fused nanocrystals.
33. The device of claim 32 , wherein the core of substantially each of the first type of fused nanocrystals is in direct physical contact and electrical communication with the core of another of the first type of fused nanocrystals.
34. The device of claim 33 , wherein the core of substantially each of the second type of fused nanocrystals is in direct physical and electrical communication with the core of another of the second type of fused nanocrystals.
35. The device of claim 22 , wherein each fused nanocrystal is of a size and composition to absorb at least one of infrared radiation, x-ray radiation, ultraviolet radiation, and visible radiation.
36. The device of claim 22 , wherein the first and second electrodes are disposed on a substrate with the film therebetween and are substantially parallel to one another.
37. The device of claim 22 , wherein the first and second electrodes are disposed on a substrate with the film therebetween and are interdigitated.
38. The device of claim 22 , wherein the first and second electrodes are spaced by about 0.2 μm to about 2 μm from each other.