PHOTOVOLTAIC DEVICES WITH INTEGRATED COLOR INTERFEROMETRIC FILM STACKS

• US 20090101192A1
• Filed: 12/28/2007
• Published: 04/23/2009
• Est. Priority Date: 10/19/2007
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm, Inc.
• Inventors: Khazeni, Kasra, Xu, Gang, Kothari, Manish
• Granted Patent: US 8,058,549 B2
• Time in Patent Office: Days
• US Class Current: 136/246
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G02B 5/285 comprising deposited thin solid films G02B5/281 - G02B5/289 take precedence; multilayered film filters for fibre optic multiplexing G02B6/29361
• CPC Class Codes: H01L 31/02165 using interference filters, e.g. multilayer dielectric filters interference filters G02B5/28
• CPC Class Codes: H01L 31/02168 the coatings being antireflective or having enhancing optical properties for the solar cells
• CPC Class Codes: H01L 31/0543 comprising light concentrating means of the refractive type, e.g. lenses
• CPC Class Codes: H01L 31/0547 comprising light concentrating means of the reflecting type, e.g. parabolic mirrors, concentrators using total internal reflection
• CPC Class Codes: Y02E 10/52 PV systems with concentrators

Abstract

Color photovoltaic (PV) devices formed using interferometric stacks tuned to reflect color covering the front side or back side of a PV cell, device, panel, or array are disclosed. Interferometric stacks covering PV devices include interferometric modulators (IMODs), or dichroic pair stacks. Such devices can be configured to reflect enough light of select wavelengths so as to impart a color, while transmitting enough light to the PV active material so as to generate useful electricity.

Claims

1. A photovoltaic device comprising:

a photovoltaic active material; and

an interferometric stack covering a first side of the photovoltaic active material, wherein the interferometric stack is configured to selectively enhance reflections of select wavelengths within a visible range of wavelengths, to reflect a visible color on the first side.

2. The device of claim 1, wherein the photovoltaic active material comprises front electrode regions on a front side of the device, and window regions on the front side of the device adjacent the front electrode regions.

3. The device of claim 2, wherein a reflectivity of visible light reflected out of the interferometric stack in front of the window regions is greater than 10% relative to visible incident light.

4. The device of claim 2, wherein a reflectivity of visible light reflected out of the interferometric stack in front of the window regions is greater than 15% relative to visible incident light.

5. The device of claim 1, wherein a reflectance at a peak wavelength is between 20% and 95%.

6. The device of claim 1, wherein a reflectance at a peak wavelength is greater than 80%.

7. The device of claim 1, wherein the first side is a light-incident side of the photovoltaic device and wherein the interferometric stack is configured to selectively transmit light through to the photovoltaic material such that the selectively transmitted light is converted to electrical current.

8. The device of claim 1, further comprising an additional film on a light-incident side of the interferometric stack.

9. The device of claim 8, wherein the additional film comprises a passivation or anti-reflection layer.

10. The device of claim 1, wherein the color reflected out of the interferometric stack is substantially uniform across the photovoltaic device.

11. The device of claim 1, wherein the photovoltaic cell comprises a photovoltaic material selected from the group consisting of single crystal silicon, amorphous silicon, germanium, III-V semiconductors, copper indium gallium selenide, cadmium telluride, gallium arsenide, indium nitride, gallium nitride, boron arsenide, indium gallium nitride, and tandem multi-junction photovoltaic materials.

12. The device of claim 1, wherein the photovoltaic cell comprises an interferometrically-enhanced photovoltaic cell.

13. The device of claim 1, wherein the interferometric stack comprises a dichroic pair of optical films.

14. The device of claim 13, wherein the interferometric stack comprises a plurality of dichroic pairs of optical films.

15. The device of claim 14, wherein the plurality of dichroic pairs comprises a number of dichroic pairs that is different for different regions across the device, each region with a different number of dichroic pairs corresponding to a different reflected color.

16. The device of claim 14, wherein a thickness of optical thin films comprising the dichroic pairs is different for different regions across the device, each region with a different optical thin film thickness corresponding to a different reflected color.

17. The device of claim 14, wherein a material comprising optical thin films comprising the dichroic pairs is different for different regions across the device, each region with a different optical thin film material corresponding to a different reflected color.

18. The device of claim 1, wherein the interferometric stack comprises an absorber and an optical resonant cavity, wherein the optical resonant cavity faces the photovoltaic active material.

19. The device of claim 18, wherein the interferometric stack further comprises a partial reflector such that the optical resonant cavity lies between the absorber and the reflector.

20. The device of claim 19, wherein the optical resonant cavity comprises an air gap having a height formed by supports separating the absorber from the partial reflector.

21. The device of claim 20, wherein the interferometric stack comprises an active microelectromechanical system (MEMS) device having a reflector that can electromagnetically change the size of the optical resonant cavity.

22. The device of claim 18, wherein the optical resonant cavity comprises a dielectric.

23. The device of claim 18, wherein the optical resonant cavity comprises a conductor.

24. The device of claim 18, wherein the optical resonant cavity comprises an optical thin film.

25. The device of claim 24, wherein the optical thin film has an index of refraction (n) between about 1 and 3.

26. The device of claim 25, wherein a thickness of the optical thin film is between about 42/n nm and 700/n nm.

27. The device of claim 24, wherein a height of the optical resonant cavity is not uniform across the device.

28. The device of claim 24, wherein the optical resonant cavity height is patterned such that the interferometric stack comprises two or more regions, each region with a different optical resonant cavity height corresponding to a different reflected color.

29. The device of claim 28, wherein the pattern comprises a regular array of pixels.

30. The device of claim 29, wherein the array of pixels comprises a plurality of red pixels, a plurality of green pixels, and a plurality of blue pixels.

31. A photovoltaic device having a front side and a back side, the device comprising:

a photovoltaic active layer; and

an interferometric modulator configured to interferometrically tune reflections, the interferometric modulator comprising;

one or more optically transparent layers forming an optical resonant cavity over the photovoltaic active layer; and

an absorber layer over the optical resonant cavity.

32. The device of claim 31, wherein the interferometric modulator extends over a portion of the photovoltaic active layer that receives light.

33. The device of claim 31, wherein the interferometric modulator is configured to selectively enhance reflection of select visible wavelengths from incident broadband visible light to reflect a color.

34. The device of claim 33, wherein the interferometric modulator is positioned over the front side of the photovoltaic active layer.

35. The device of claim 34, wherein the interferometric modulator is configured to selectively transmit light through to the photovoltaic active layer for conversion to electrical current.

36. The device of claim 33, wherein the interferometric modulator is positioned over the back side of the photovoltaic active layer.

37. A photovoltaic device, the device comprising:

a photovoltaic active layer; and

a dichroic stack configured to interferometrically tune light reflections and transmissions, the dichroic stack comprising one or more pairs of dielectric films, wherein each of the one or more pairs comprise one film with a first index of refraction over another film with a lower index of refraction.

38. The device of claim 37, wherein the dichroic stack extends over a part of the photovoltaic active layer that receives light for conversion to electrical current.

39. The device of claim 37, wherein the dichroic stack is configured to selectively reflect a range of visible wavelengths to display a color.

40. The device of claim 39, wherein the dichroic stack is positioned over a front side of the photovoltaic active layer.

41. The device of claim 40, wherein the dichroic stack is configured to selectively transmit a range of visible wavelengths through to the photovoltaic active layer.

42. The device of claim 39, wherein the dichroic stack is positioned over a back side of the photovoltaic active layer.

43. The device of claim 37, wherein the dichroic stack is positioned over a back side of the photovoltaic active layer.

45. The method of claim 43, wherein forming the interferometric stack comprises:

forming an optical resonant cavity over the photovoltaic material; and

forming a layer of light absorbing material onto the optical resonant cavity.

46. The method of claim 45, further comprising forming a layer of partially reflecting and partially transmitting material, wherein forming an optical resonant cavity comprises forming the optical resonant cavity onto the layer of partially reflecting and partially transmitting material.

47. The method of claim 46, wherein the layer of light absorbing material is in front of the optical resonant cavity, and the optical resonant cavity is in front of the partially reflecting and partially transmitting material.

48. The method of claim 45, wherein forming the interferometric stack over the photovoltaic material comprises forming the interferometric stack onto the front side of the photovoltaic material.

49. The method of claim 45, wherein forming the interferometric stack over the photovoltaic material comprises forming the interferometric stack over the back of a back electrode on the back side of the photovoltaic material.

50. The method of claim 45, wherein forming the interferometric stack over the photovoltaic material further comprises forming the interferometric stack onto a transparent substrate.

51. The method of claim 50, further comprising laminating the transparent substrate over the front side of the photovoltaic material.

52. The method of claim 50, further comprising laminating the transparent substrate over the back side of the photovoltaic material.

53. The method of claim 45, wherein forming the optical resonant cavity comprises forming different thicknesses of one or more optically transparent layers over different regions of the photovoltaic device, each different thickness corresponding to a different interferometrically enhanced visible color reflected from the interferometric stack.

54. The method of claim 43, wherein forming the interferometric stack comprises forming a dichroic stack configured to interferometrically enhance reflections of a particular color over the photovoltaic material.

55. The method of claim 54, wherein forming the dichroic stack over the photovoltaic material comprises forming the dichroic stack over the front side of the photovoltaic material.

56. The method of claim 54, wherein forming the dichroic stack over the photovoltaic material further comprises forming the dichroic stack onto a transparent substrate.

57. The method of claim 56, further comprising laminating the transparent substrate onto the front or back side of the photovoltaic material.

58. The method of claim 54, wherein forming the dichroic stack comprises forming optical thin films of different thickness over different regions of the photovoltaic device, each different thickness corresponding to a different interferometrically enhanced visible color reflected from the interferometric stack.

44. A method of manufacturing a color photovoltaic device, the method comprising:

providing a photovoltaic material having a front side on which light is incident and a back side; and

forming an interferometric stack over the photovoltaic material, the interferometric stack configured to interferometrically enhance visible light reflections of a particular color.

59. A photovoltaic device comprising:

means for generating an electrical current from incident light; and

means for interferometrically enhancing reflected visible light of a particular color from a first side of the photovoltaic device.

60. The device of claim 59, wherein the means for generating the electrical current comprises a semiconductor photovoltaic active material.

61. The device of claim 59, wherein the means for interferometrically enhancing reflected light comprises a thin film stack including an optical resonant cavity and an absorber over a light-incident side of the photovoltaic device.

62. The device of claim 61, wherein the means for interferometrically reflecting light further comprises a partial reflector between the optical resonant cavity and the means for generating an electrical current from incident light.

63. The device of claim 59, wherein the means for interferometrically reflecting light comprises a stack including a plurality of dichroic pairs of optical thin films, wherein an index of refraction of a first optical thin film of each pair is higher than an index of refraction of a second thin film for each pair.