Methods of making quantum dot films

• US 8,054,671 B2
• Filed: 05/14/2010
• Issued: 11/08/2011
• Est. Priority Date: 01/07/2005
• Status: Active Grant

• Current Assignee: InVisage Technologies, Inc. (Apple Inc.)
• Original Assignee: InVisage Technologies, Inc. (Apple Inc.)
• Inventors: Konstantatos, Gerasimos, Howard, Ian, Sargent, Edward, Levina, Larissa, Klem, Ethan J. D., Clifford, Jason
• Primary Examiner(s): Elms; Richard
• Assistant Examiner(s): Byrne; Harry W
• Application Number:
  US12/780,026
• Publication Number:
  US 20100317175A1
• Time in Patent Office: 543 Days
• Field of Search: 365/161, 365/163, 365/129, 257/1, 257 14- 25, 257/59, 257/72, 257/250, 257/E29.071, 257/E25.004, 257/E27.083, 257/E27.16, 438/48, 438/197, 438/479, 438/590, 438/962, 428/403, 428/407, 252/301.4, 252/301.6, 977/708, 977/774, 977/775, 977/773, 977/778, 977/759, 977/847, 372/43, 435/472, 424/484, 385/122, 600/425
• US Class Current: 365/129
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C30B 29/605 Products containing multiple oriented crystallites, e.g. columnar crystallites
• CPC Class Codes: C30B 7/005 Epitaxial layer growth
• CPC Class Codes: G06F 30/00 Computer-aided design [CAD]
• CPC Class Codes: H01L 21/02422 Non-crystalline insulating materials, e.g. glass, polymers
• CPC Class Codes: H01L 21/02521 Materials
• CPC Class Codes: H01L 21/02601 Nanoparticles fullerenes H10K85/211
• CPC Class Codes: H01L 21/02628 using solutions
• CPC Class Codes: H01L 27/14601 Structural or functional details thereof
• CPC Class Codes: H01L 29/22 including, apart from doping materials or other impurities, only AIIBVI compounds
• CPC Class Codes: H01L 31/0352 characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
• CPC Class Codes: H10K 10/466 Lateral bottom-gate IGFETs comprising only a single gate
• CPC Class Codes: H10K 10/488 the channel region comprising a layer of composite material having interpenetrating or embedded materials, e.g. a mixture of donor and acceptor moieties, that form a bulk heterojunction
• CPC Class Codes: H10K 30/30 comprising bulk heterojunctions, e.g. interpenetrating networks of donor and acceptor material domains
• CPC Class Codes: H10K 30/35 comprising inorganic nanostructures, e.g. CdSe nanoparticles
• CPC Class Codes: H10K 39/30 Devices controlled by radiation
• CPC Class Codes: H10K 85/114 Poly-phenylenevinylene; Derivatives thereof
• CPC Class Codes: Y02E 10/549 Organic PV cells
• CPC Class Codes: Y10S 438/962 Quantum dots and lines
• CPC Class Codes: Y10S 977/773 : Nanoparticle, i.e. structure having three dimensions of 100 nm or less
• CPC Class Codes: Y10S 977/774 : Exhibiting three-dimensional carrier confinement, e.g. quantum dots

Abstract

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.

Claims

1. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface, the fabricating of the plurality of nanocrystals comprising forming the nanocrystals in a substantially inert environment so as to substantially prevent the formation of defect states on the outer surfaces of the nanocrystals;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity; and

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals.

2. The method of claim 1, wherein the second length is less than the first length.

3. The method of claim 1, wherein said first ligands each comprise a carbon chain greater than about 10 carbons long.

4. The method of claim 1, wherein said second ligands each comprise a carbon chain between about 1 to 10 carbons long.

5. The method of claim 1, wherein said second ligands have a length less than about 1 nm.

6. The method of claim 1, wherein said second ligands comprise at least one of pyridine, allylamine, methylamine, ethylamine, propylamine, butylamine, octylamine, and pyrrolidine.

7. The method of claim 1, wherein the second ligands bind to the outer surface of the nanocrystals with an affinity that is at least as large as an affinity with which the first ligands bind to the outer surface of the nanocrystals.

8. The method of claim 1, wherein exchanging the plurality of first ligands for a plurality of second ligands comprises precipitating the fabricated nanocrystals;

washing the precipitated nanocrystals; and

dispersing the washed nanocrystals in a solution comprising the second ligands.

9. The method of claim 1, wherein forming the film of ligand-exchanged nanocrystals comprises solution-depositing the ligand-exchanged nanocrystals onto a substrate.

10. The method of claim 9, wherein solution-depositing the ligand-exchanged nanocrystals comprises spray-coating, dip-casting, drop-casting, evaporating, blade-casting, or spin-coating the ligand-exchanged nanocrystals onto the substrate.

11. The method of claim 1, wherein removing the second ligands comprises volatilizing the second ligands during the step of fusing the cores of adjacent nanocrystals.

12. The method of claim 11, wherein volatilizing the second ligands causes a relatively small change in the volume of the film of ligand-exchanged nanocrystals.

13. The method of claim 1, wherein the volume changes by less than about 30% during ligand removal.

14. The method of claim 1, wherein removing the second ligands comprises performing a chemical transformation of the ligands so as to remove them.

15. The method of claim 1, wherein fusing the cores of adjacent nanocrystals comprises annealing the film of ligand-exchanged nanocrystals.

16. The method of claim 1, wherein fusing the cores of adjacent nanocrystals forms a substantially inorganic film having nanoscale features.

17. The method of claim 16, wherein the nanoscale features have about the same size and shape of the individual nanocrystals before they were fused.

18. The method of claim 1, comprising fusing the cores of adjacent nanocrystals to an extent that the nanocrystals substantially maintain their individual properties but are joined by regions through which current readily flows.

19. The method of claim 18, wherein a central absorption wavelength of the nanocrystals changes by less than about 10% when fused to one or more adjacent nanocrystals.

20. The method of claim 1, wherein fusing the cores of adjacent nanocrystals comprises annealing the nanocrystals at a temperature of between 150°

C. and 450°

C.

21. The method of claim 1, wherein fusing the cores of adjacent nanocrystals comprises annealing the film at a temperature of between room temperature and 150°

C.

22. The method of claim 1, further comprising modifying the outer surfaces of the fused nanocrystals including depositing a semiconductor shell on the fused nanocrystals.

23. The method of claim 1, further comprising modifying the outer surfaces of the fused nanocrystals including forming one or more defect states on the outer surfaces of the fused nanocrystals.

24. A method of forming a device, the method comprising:

(a) forming a film of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of ligands being attached to the outer surface, at least a portion of the nanocrystals being in physical contact with at least one adjacent nanocrystals;

(b) removing the ligands from at least a portion of the nanocrystals;

(c) annealing the film of nanocrystals so as to fuse the cores of the nanocrystals to the cores at least one adjacent nanocrystal and thus form an electrical network of fused nanocrystals;

(d) providing first and second electrodes in spaced relation and in electrical communication with first and second portions of the electrical network of fused nanocrystals; and

(e) substituting a plurality of the ligands with a plurality of shorter ligands.

25. The method of claim 24, wherein substituting a plurality of said ligands with a plurality of shorter ligands decreases an effective distance between at least one nanocrystals and at least one adjacent nanocrystal.

26. The method of claim 24, further comprising altering the composition of the outer surfaces of the nanocrystals.

27. The method of claim 24, further comprising creating at least one defect state on the outer surface of at least some of the fused nanocrystals and not creating a defect state in the regions where one nanocrystal core is fused to another, wherein the at least one defect state comprises at least one trap state for a hole during operation of the device.

28. The method of claim 24, wherein forming the film of nanocrystals comprises solution-depositing colloidal nanocrystals on the substrate.

29. The method of claim 28, wherein solution-depositing colloidal nanocrystals comprises spray-coating, dip-casting, drop-casting, evaporating, blade-casting, or spin-coating the nanocrystals onto the substrate.

30. The method of claim 24, wherein the first and second electrodes are spaced from each other by between about 0.2 and 2μ

m.

31. The method of claim 24, wherein providing first and second electrodes in spaced relation and in electrical communication with the electrical network of fused nanocrystals comprises forming the first and second electrodes on a substrate and subsequently performing steps (a)-(c), the first and second electrodes having a parallel orientation relative to one another.

32. The method of claim 24, wherein providing first and second electrodes in spaced relation and in electrical communication with the electrical network of fused nanocrystals comprises forming the first electrode on the substrate, subsequently performing steps (a)-(c), and subsequently providing the second electrode over the electrical network of fused nanocrystals.

33. The method of claim 32, wherein the second electrode comprises at least one of aluminum, gold, platinum, silver, magnesium, copper, indium tin oxide (ITO), tin oxide, tungsten oxide, and combinations and layer structures thereof.

34. The method of claim 32, wherein the second electrode is at least partially optically transparent.

35. The method of claim 32, wherein the second electrode comprises at least one of a bandpass filter and a bandblock filter.

36. A method of forming a nanocrystalline film from a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of ligands being attached to the outer surface, the method comprising:

(a) forming a film of ligand-attached nanocrystals, at least a portion of the ligand-attached nanocrystals being adjacent at least one other ligand-attached nanocrystal, the ligands each comprising a carbon chain between about 1 to 10 carbons long;

(b) removing the ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals; and

(c) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals.

37. The method of claim 36, wherein said ligands have a length less than about 1 nm.

38. The method of claim 36, wherein forming the film of ligand-attached nanocrystals comprises solution-depositing the ligand-exchanged nanocrystals onto a substrate.

39. The method of claim 38, wherein solution-depositing the ligand-exchanged nanocrystals comprises spray-coating, dip-casting, drop-casting, evaporating, blade-casting, or spin-coating the ligand-exchanged nanocrystals onto the substrate.

40. The method of claim 36, wherein removing the ligands comprises volatilizing the ligands during the step of fusing the cores of adjacent nanocrystals.

41. The method of claim 36, wherein fusing the cores of adjacent nanocrystals comprises annealing the film of ligand-attached nanocrystals.

42. The method of claim 36, wherein fusing the cores of adjacent nanocrystals comprises annealing the nanocrystals at a temperature between room temperature and about 450°

C.

43. The method of claim 36, further comprising modifying the outer surfaces of the fused nanocrystals, wherein modifying the outer surfaces comprises depositing a semiconductor shell on the fused nanocrystals.

44. The method of claim 36, further comprising modifying the outer surfaces of the fused nanocrystals, wherein modifying the outer surface comprises forming one or more defect states on the outer surfaces of the fused nanocrystals.

45. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands, the second length being less than the first length;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity; and

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals.

46. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface, each of the plurality of first ligands comprising a carbon chain greater than about 10 carbons long;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity; and

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals.

47. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands, each of the plurality of second ligands comprising a carbon chain between about 1 to 10 carbons long;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity; and

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals.

48. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands, each of the plurality of second ligands having a length less than about 1 nm;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity; and

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals.

49. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands, the second ligands comprising at least one of pyridine, allylamine, methylamine, ethylamine, propylamine, butylamine, octylamine, and pyrrolidine;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity; and

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals.

50. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands, the second ligands binding to the outer surface of the nanocrystals with an affinity that is at least as large as an affinity with which the first ligands bind to the outer surface of the nanocrystals;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity; and

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals.

51. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands, the exchanging the plurality of first ligands for a plurality of second ligands comprising precipitating the fabricated nanocrystals;

washing the precipitated nanocrystals; and

dispersing the washed nanocrystals in a solution comprising the second ligands;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity; and

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals.

52. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal, the forming of the film of ligand-exchanged nanocrystals comprising solution-depositing the ligand-exchanged nanocrystals onto a substrate;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity; and

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals.

53. The method of claim 52, wherein solution-depositing the ligand-exchanged nanocrystals comprises spray-coating, dip-casting, drop-casting, evaporating, blade-casting, or spin-coating the ligand-exchanged nanocrystals onto the substrate.

54. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity, the removing of the second ligands comprises volatilizing the second ligands during the step of fusing the cores of adjacent nanocrystals; and

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals.

55. The method of claim 54, wherein volatilizing the second ligands causes a relatively small change in the volume of the film of ligand-exchanged nanocrystals.

56. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity, the volume changing by less than about 30% during ligand removal; and

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals.

57. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity, the removing of the second ligands comprises performing a chemical transformation of the ligands so as to remove them; and

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals.

58. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity; and

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals, the fusing the cores of adjacent nanocrystals comprising annealing the film of ligand-exchanged nanocrystals.

59. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity; and

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals, the fusing of the cores of adjacent nanocrystals forms a substantially inorganic film having nanoscale features.

60. The method of claim 59, wherein the nanoscale features have about the same size and shape of the individual nanocrystals before they were fused.

61. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity; and

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals, the fusing of the cores of adjacent nanocrystals being to an extent that the nanocrystals substantially maintain their individual properties but are joined by regions through which current readily flows.

62. The method of claim 61, wherein a central absorption wavelength of the nanocrystals changes by less than about 10% when fused to one or more adjacent nanocrystals.

63. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity; and

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals, the fusing the cores of adjacent nanocrystals comprises annealing the nanocrystals at a temperature of between 150°

C. and 450°

C.

64. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity; and

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals, the fusing the cores of adjacent nanocrystals comprises annealing the film at a temperature of between room temperature and 150°

C.

65. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity;

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals; and

(f) modifying the outer surfaces of the fused nanocrystals including depositing a semiconductor shell on the fused nanocrystals.

66. A method of forming a nanocrystalline film, the method comprising:

(a) fabricating a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of first ligands having a first length being attached to the outer surface;

(b) exchanging the plurality of first ligands attached to the outer surface of the nanocrystals for a plurality of second ligands having a second length and having a different chemical composition than the plurality of first ligands;

(c) forming a film of ligand-exchanged nanocrystals, wherein at least a portion of the ligand-exchanged nanocrystals are adjacent at least one other ligand-exchanged nanocrystal;

(d) removing the second ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals so as to bring the outer surfaces of adjacent nanocrystals into closer proximity; and

(e) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals; and

(f) modifying the outer surfaces of the fused nanocrystals including forming one or more defect states on the outer surfaces of the fused nanocrystals.

67. A method of forming a device, the method comprising:

(a) forming a film of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of ligands being attached to the outer surface, at least a portion of the nanocrystals being in physical contact with at least one adjacent nanocrystals;

(b) removing the ligands from at least a portion of the nanocrystals;

(c) annealing the film of nanocrystals so as to fuse the cores of the nanocrystals to the cores at least one adjacent nanocrystal and thus form an electrical network of fused nanocrystals;

(d) providing first and second electrodes in spaced relation and in electrical communication with first and second portions of the electrical network of fused nanocrystals; and

(e) altering the composition of the outer surfaces of the nanocrystals.

68. A method of forming a device, the method comprising:

(a) forming a film of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of ligands being attached to the outer surface, at least a portion of the nanocrystals being in physical contact with at least one adjacent nanocrystals;

(b) removing the ligands from at least a portion of the nanocrystals;

(c) annealing the film of nanocrystals so as to fuse the cores of the nanocrystals to the cores at least one adjacent nanocrystal and thus form an electrical network of fused nanocrystals;

(d) providing first and second electrodes in spaced relation and in electrical communication with first and second portions of the electrical network of fused nanocrystals; and

(e) creating at least one defect state on the outer surface of at least some of the fused nanocrystals and not creating a defect state in the regions where one nanocrystal core is fused to another, the at least one defect state comprising at least one trap state for a hole during operation of the device.

69. A method of forming a device, the method comprising:

(a) forming a film of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of ligands being attached to the outer surface, at least a portion of the nanocrystals being in physical contact with at least one adjacent nanocrystals, the forming of the film of nanocrystals comprises solution-depositing colloidal nanocrystals on the substrate;

(b) removing the ligands from at least a portion of the nanocrystals;

(c) annealing the film of nanocrystals so as to fuse the cores of the nanocrystals to the cores at least one adjacent nanocrystal and thus form an electrical network of fused nanocrystals;

and (d) providing first and second electrodes in spaced relation and in electrical communication with first and second portions of the electrical network of fused nanocrystals.

70. The method of claim 69, wherein solution-depositing colloidal nanocrystals comprises spray-coating, dip-casting, drop-casting, evaporating, blade-casting, or spin-coating the nanocrystals onto the substrate.

71. A method of forming a device, the method comprising:

(a) forming a film of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of ligands being attached to the outer surface, at least a portion of the nanocrystals being in physical contact with at least one adjacent nanocrystals;

(b) removing the ligands from at least a portion of the nanocrystals;

(c) annealing the film of nanocrystals so as to fuse the cores of the nanocrystals to the cores at least one adjacent nanocrystal and thus form an electrical network of fused nanocrystals; and

(d) providing first and second electrodes in spaced relation and in electrical communication with first and second portions of the electrical network of fused nanocrystals, the first and second electrodes being spaced from each other by between about 0.2μ

m and 2μ

m.

72. A method of forming a device, the method comprising:

(a) forming a film of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of ligands being attached to the outer surface, at least a portion of the nanocrystals being in physical contact with at least one adjacent nanocrystals;

(b) removing the ligands from at least a portion of the nanocrystals;

(c) annealing the film of nanocrystals so as to fuse the cores of the nanocrystals to the cores at least one adjacent nanocrystal and thus form an electrical network of fused nanocrystals; and

(d) providing first and second electrodes in spaced relation and in electrical communication with first and second portions of the electrical network of fused nanocrystals, the providing of the first and the second electrodes in spaced relation and in electrical communication with the electrical network of fused nanocrystals comprises forming the first and second electrodes on a substrate and subsequently performing steps (a) through (c), the first and second electrodes having a parallel orientation relative to one another.

73. A method of forming a device, the method comprising:

(a) forming a film of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of ligands being attached to the outer surface, at least a portion of the nanocrystals being in physical contact with at least one adjacent nanocrystals;

(b) removing the ligands from at least a portion of the nanocrystals;

(c) annealing the film of nanocrystals so as to fuse the cores of the nanocrystals to the cores at least one adjacent nanocrystal and thus form an electrical network of fused nanocrystals; and

(d) providing first and second electrodes in spaced relation and in electrical communication with first and second portions of the electrical network of fused nanocrystals, the providing of the first and the second electrodes in spaced relation and in electrical communication with the electrical network of fused nanocrystals comprises forming the first electrode on the substrate, subsequently performing steps (a) through (c), and subsequently providing the second electrode over the electrical network of fused nanocrystals.

74. The method of claim 73, wherein the second electrode comprises at least one of aluminum, gold, platinum, silver, magnesium, copper, indium tin oxide (ITO), tin oxide, tungsten oxide, and combinations and layer structures thereof.

75. The method of claim 73, wherein the second electrode is at least partially optically transparent.

76. The method of claim 73, wherein the second electrode comprises at least one of a bandpass filter and a bandblock filter.

77. A method of forming a nanocrystalline film from a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of ligands being attached to the outer surface, the method comprising:

(a) forming a film of ligand-attached nanocrystals, at least a portion of the ligand-attached nanocrystals being adjacent at least one other ligand-attached nanocrystal, the ligands having a length less than about 1 nm;

(b) removing the ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals; and

(c) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals.

78. A method of forming a nanocrystalline film from a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of ligands being attached to the outer surface, the method comprising:

(a) forming a film of ligand-attached nanocrystals, at least a portion of the ligand-attached nanocrystals being adjacent at least one other ligand-attached nanocrystal, the forming the film of ligand-attached nanocrystals comprising solution-depositing the ligand-exchanged nanocrystals onto a substrate;

(b) removing the ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals; and

(c) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals.

79. The method of claim 78, wherein solution-depositing the ligand-exchanged nanocrystals comprises spray-coating, dip-casting, drop-casting, evaporating, blade-casting, or spin-coating the ligand-exchanged nanocrystals onto the substrate.

80. A method of forming a nanocrystalline film from a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of ligands being attached to the outer surface, the method comprising:

(a) forming a film of ligand-attached nanocrystals, at least a portion of the ligand-attached nanocrystals being adjacent at least one other ligand-attached nanocrystal;

(b) removing the ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals, the removing the ligands comprising volatilizing the ligands during the step of fusing the cores of adjacent nanocrystals; and

(c) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals.

81. A method of forming a nanocrystalline film from a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of ligands being attached to the outer surface, the method comprising:

(a) forming a film of ligand-attached nanocrystals, at least a portion of the ligand-attached nanocrystals being adjacent at least one other ligand-attached nanocrystal;

(b) removing the ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals; and

(c) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals, the fusing the cores of adjacent nanocrystals comprising annealing the film of ligand-attached nanocrystals.

82. A method of forming a nanocrystalline film from a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of ligands being attached to the outer surface, the method comprising:

(a) forming a film of ligand-attached nanocrystals, at least a portion of the ligand-attached nanocrystals being adjacent at least one other ligand-attached nanocrystal;

(b) removing the ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals; and

(c) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals, the fusing the cores of adjacent nanocrystals comprising annealing the nanocrystals at a temperature between room temperature and about 450°

C.

83. A method of forming a nanocrystalline film from a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of ligands being attached to the outer surface, the method comprising:

(a) forming a film of ligand-attached nanocrystals, at least a portion of the ligand-attached nanocrystals being adjacent at least one other ligand-attached nanocrystal;

(b) removing the ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals;

(c) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals; and

(d) modifying the outer surfaces of the fused nanocrystals, the modifying of the outer surfaces comprises depositing a semiconductor shell on the fused nanocrystals.

84. A method of forming a nanocrystalline film from a plurality of nanocrystals, the nanocrystals having a core and an outer surface, a plurality of ligands being attached to the outer surface, the method comprising:

(a) forming a film of ligand-attached nanocrystals, wherein at least a portion of the ligand-attached nanocrystals are adjacent at least one other ligand-attached nanocrystal;

(b) removing the ligands attached to the outer surfaces of the nanocrystals of the film of ligand-exchanged nanocrystals;

(c) fusing the cores of adjacent nanocrystals so as to form an electrical network of fused nanocrystals; and

(d) modifying the outer surfaces of the fused nanocrystals, the modifying of the outer surface comprises forming one or more defect states on the outer surfaces of the fused nanocrystals.