Carbon Nanotubes As Charge Carriers In Organic and Hybrid Solar Cells

• US 20090205713A1
• Filed: 02/19/2008
• Published: 08/20/2009
• Est. Priority Date: 02/19/2008
• Status: Active Grant

• Current Assignee: New Jersey Institute of Technology
• Original Assignee: New Jersey Institute of Technology
• Inventors: Li, Cheng, Mitra, Somenath
• Granted Patent: US 9,293,720 B2
• Time in Patent Office: Days
• US Class Current: 136/263
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: H10K 30/30 comprising bulk heterojunctions, e.g. interpenetrating networks of donor and acceptor material domains
• CPC Class Codes: H10K 30/50 Photovoltaic [PV] devices
• CPC Class Codes: H10K 85/113 Heteroaromatic compounds comprising sulfur or selene, e.g. polythiophene
• CPC Class Codes: H10K 85/211 Fullerenes, e.g. C60
• CPC Class Codes: H10K 85/221 Carbon nanotubes
• CPC Class Codes: Y02E 10/549 Organic PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

Organic and organic/inorganic hybrid bulk heterojunction photovoltaic devices with improved efficiencies are disclosed. The organic photovoltaic device comprises a photoactive polymer:fullerene C₆₀-carbon nanotube (polymer:C₆₀-CNT) composite as a component of the active layer. Under light irradiation, photoinduced charge separation at the polymer:C₆₀ interface is followed by electron transfer from C₆₀ onto CNTs for efficient electron transport towards an electrode. The organic/inorganic hybrid photovoltaic device comprises quantum dots and carbon nanotubes. Power conversion efficiency enhancement methods of polymer-CNT based photovoltaics are also provided.

Claims

1. An organic or organic/inorganic hybrid photovoltaic conversion device comprising:

a photoactive polymer;

fullerene C₆₀ (C₆₀);

soluble or dispersible single or multiwalled carbon nanotubes (CNTs); and

an electrode adapted to collect current.

2. The device of claim 1, wherein the photoactive polymer acts as an electron donor, the fullerene C₆₀ acts as an electron acceptor, and the CNTs act as an electron transporter to the electrode.

3. The device of claim 1, wherein the photoactive polymer, the fullerene C₆₀, CNTs and electrode are positioned in a photoactive layer.

4. The device of claim 1, wherein the fullerene C₆₀ and CNTs form a weakly, covalently bonded complex or self-assembled complex.

5. The device of claim 1, wherein the soluble or dispersible CNTs are synthesized by a microwave reaction.

6. The device of claim 1, further comprising a planarizing layer of PEDOT:

PSS.

7. The device of claim 1, wherein the photoactive polymer is selected from the group consisting of P3HT, a liquid crystal polymer, a semiconducting polymer and combinations thereof.

8. The device of claim 1, wherein the fullerene C₆₀ and the CNTs form a complex and wherein said complex and the photoactive polymer form a composite.

9. The device of claim 8, wherein the composite is structurally ordered in a controlled manner.

10. The device of claim 9, wherein the controlled manner comprises solvent vapor annealing followed by thermal annealing.

11. The device of claim 9, wherein the controlled manner comprises solvent vapor annealing, thermal annealing or both.

12. The device of claim 11, wherein solvent annealing is undertaken with a solvent selected from the group consisting of toluene, an alkene, an alkane, hexane, an alcohol, a chlorinated solvent, or an organic solvent.

13. The device of claim 11, wherein the solvent annealing is performed for 5 or less minutes.

14. The device of claim 11, wherein the thermal annealing is performed at 135°

C. or less.

15. The device of claim 1, wherein the device comprises a solar cell.

16. The device of claim 1, wherein the photoactive polymer, the fullerene C₆₀, the CNTs and the electrode are positioned in a photoactive layer, and wherein said photoactive layer is formed on a flexible substrate.

17. The device of claim 16, wherein the device is characterized by an overall stiffness that is determined by the stiffness of the flexible substrate.

18. The device of claim 1, further comprising quantum dots (QDs).

19. The device of claim 18, wherein the QDs are dispersed in the photoactive polymer.

20. The device of claim 18, wherein QDs coat or decorate the CNTs.

21. The device of claim 18, wherein the absorption spectra of the QDs and the photoactive polymer are complementary.

22. The device of claim 1, further comprising at least one dye or titanium dioxide at a level effective to enhance absorption, power conversion efficiency or both.

23. The device of claim 1, wherein the CNTs are aligned in an electrical field.

24. A method for making an organic or organic/inorganic hybrid photovoltaic conversion device, comprising:

synthesizing soluble or dispersible single or multiwalled carbon nanotubes (CNTs);

preparing a complex of fullerene C₆₀ and the CNTs;

incorporating said C₆₀-CNT complex in a polymer;

solvent vapor annealing; and

thermal annealing.

25. The method of claim 24, wherein the step of synthesizing soluble or dispersible carbon nanotubes comprises a microwave reaction in the presence of a chemical or combination of chemicals selected from the group consisting of carboxylated, sulfonated, nitro, amino, and ester chemical groups.

26. The method of claim 24, wherein the step of synthesizing soluble or dispersible carbon nanotubes comprises a microwave reaction in the presence of sulfuric and nitric acid.

27. The method of claim 24, wherein the step of preparing a complex of fullerene C₆₀ and CNTs comprises:

preparing a bulk solution of fullerene C₆₀ in toluene; and

combining said bulk solution of fullerene C₆₀ and a solution of CNTs.

28. The method of claim 27, wherein the step of combining the bulk solution of fullerene C₆₀ and a solution of CNTs further comprises:

sonicating; and

microwave irradiating the mixture.

29. The method of claim 24, wherein the C₆₀-CNT complex and the polymer form a composite.

30. The method of claim 24, wherein the polymer is selected from the group consisting of P3HT, a liquid crystal polymer, a semiconducting polymer and combinations thereof.

31. The method of claim 24, wherein the step of solvent vapor annealing is carried out before the step of thermal annealing.

32. The method of claim 24, wherein the parameters of solvent vapor annealing and thermal annealing enhance the power conversion efficiency of the device.

33. The method of claim 24, wherein the C₆₀-CNT complex and the polymer form a composite and wherein the steps of solvent vapor annealing and thermal annealing enhance phase separation at a polymer:

C₆₀ interface and ordering of said composite.

34. The method of claim 24, wherein the solvent is selected from the group consisting of toluene, an alkene, an alkane, hexane, a chlorinated solvent, an alcohol or an organic solvent.

35. The method of claim 24, wherein the device comprises a solar cell.

36. The method of claim 24, further comprising the step of dispersing quantum dots in the polymer.

37. The method of claim 36, wherein the absorption spectra of the QDs and the polymer are complementary.

38. The method of claim 24, further comprising the step of coating or decorating the CNTs with QDs.

39. The method of claim 24, further comprising the step of aligning the CNTs in an electrical field.

40. A thermal and vapor solvent annealed organic or organic/inorganic hybrid photovoltaic conversion device, comprising:

a polymer as an electron donator;

C₆₀ as an electron acceptor; and

CNTs as a means of electron transport to at least one electrode.

41. The device of claim 40, further comprising QDs dispersed in the polymer.

42. The device of claim 40, further comprising QDs coated or decorated on the CNTs.

43. The device of claim 40, wherein the CNTs are aligned in an electrical field.

44. The device of claim 40, further comprising at least one dye or titanium dioxide at a level effective to enhance absorption, power conversion efficiency or both.