Photovoltaic Modules Having a Filling Material

• US 20090014055A1
• Filed: 09/22/2008
• Published: 01/15/2009
• Est. Priority Date: 03/18/2006
• Status: Abandoned Application

• Current Assignee: Solyndra Residual Trust
• Original Assignee: Solyndra Incorporated
• Inventors: Buller, Benyamin, Beck, Markus E., Cumpston, Brian H.
• Application Number:
  US12/235,195
• Publication Number:
  US 20090014055A1
• Time in Patent Office: Days
• US Class Current: 136/246
• CPC Class Codes: H01L 31/02168 the coatings being antireflective or having enhancing optical properties for the solar cells
• CPC Class Codes: H01L 31/022433 Particular geometry of the grid contacts
• CPC Class Codes: H01L 31/035281 Shape of the body
• CPC Class Codes: H01L 31/046 PV modules composed of a plurality of thin film solar cells deposited on the same substrate
• CPC Class Codes: H01L 31/0463 characterised by special patterning methods to connect the PV cells in a module, e.g. laser cutting of the conductive or active layers
• CPC Class Codes: H01L 31/048 Encapsulation of modules
• CPC Class Codes: H01L 31/0481 characterised by the composition of the encapsulation material
• CPC Class Codes: H01L 31/0504 specially adapted for series or parallel connection of solar cells in a module
• 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: H01L 31/055 where light is absorbed and re-emitted at a different wavelength by the optical element directly associated or integrated with the PV cell, e.g. by using luminescent material, fluorescent concentrators or up-conversion arrangements
• CPC Class Codes: Y02E 10/52 PV systems with concentrators

Abstract

A photovoltaic module comprising an elongated substrate in which at least a portion of the elongated substrate is rigid is provided. One or more solar cells are disposed on the elongated substrate and each comprise: (i) a back-electrode disposed on the elongated substrate, (ii) a semiconductor junction layer disposed on all or a portion of a surface of the back-electrode, and (iii) a transparent conductive layer, having a first refractive index, is disposed on all or a portion of a surface of the semiconductor junction. The photovoltaic module further comprises a filler material, having a second refractive index that is smaller or equal in value to the first refractive index, disposed on the transparent conductive layer of the one or more solar cells. The photovoltaic module further comprises a transparent casing disposed on the filler material thereby sealing the photovoltaic module.

Claims

1. A photovoltaic module comprising:

(A) an elongated substrate wherein at least a portion of the elongated substrate is rigid, the elongated substrate having a width dimension and a longitudinal dimension;

(B) one or more solar cells disposed on said elongated substrate, said one or more solar cells each comprising;

a back-electrode disposed on a surface of the elongated substrate;

a semiconductor junction layer disposed on all or a portion of a surface of said back-electrode; and

a transparent conductive layer disposed on all or a portion of a surface of the semiconductor junction, wherein said transparent conductive layer has a first refractive index;

(C) a filler material disposed on the transparent conductive layer of each of the one or more solar cells, wherein the filler material has a second refractive index that is smaller or equal in value to said first refractive index; and

(D) a transparent casing disposed on said filler material thereby sealing said photovoltaic module, wherein said transparent casing has a third refractive index.

2. The photovoltaic module of claim 1, wherein said second refractive index has a value approximately equal to said third refractive index plus X, where X is half the absolute difference between the values of said first refractive index and said third refractive index.

3. The solar cell unit of claim 1, wherein said second refractive index is approximately equal to said first refractive index.

4. The photovoltaic module of claim 1, wherein said second refractive index is approximately equal to said third refractive index.

5. The photovoltaic module of claim 1, wherein said first and second refractive indexes are chosen to minimize the reflection of light on a surface of said transparent conductive layer.

6. The photovoltaic module of claim 1, wherein said third refractive index is in the range of 1.2 to 1.9.

7. The photovoltaic module of claim 1, wherein said third refractive index is in the range of 1.1 to 2.

8. The photovoltaic module of claim 1, wherein said second refractive index is in the range of 1.2 to 1.9.

9. The photovoltaic module of claim 1, wherein said second refractive index is approximately equal to 1.6.

10. The photovoltaic module of claim 1, wherein said first refractive index is greater or equal to 1.5.

11. The photovoltaic module of claim 1, wherein said first refractive index is greater or equal to 1.6.

12. The photovoltaic module of claim 1, wherein said first, second, and third refractive indexes are chosen such that light incident on said transparent casing is refracted towards the center of said photovoltaic module.

13. The photovoltaic module of claim 1, wherein a first solar cell in said one or more solar cells has a first surface area and said transparent casing has a second surface area, and wherein said first, second, and third refractive indexes are chosen such that said first solar cell has an effective optical surface area approximately equal to the second surface area.

14. The photovoltaic module of claim 1, wherein said second and third refractive indexes are chosen to minimize the reflection of light on the surface of said filler material.

15. The photovoltaic module of claim 1, wherein said filler material comprises ethylene vinyl acetate (EVA), silicone, silicone gel, a silicone-based oil, epoxy, polydimethyl siloxane (PDMS), RTV silicone rubber, polyvinyl butyral (PVB), thermoplastic polyurethane (TPU), a polycarbonate, an acrylic, a fluoropolymer, or a urethane.

16. The photovoltaic module of claim 1, wherein said filler material is a polydimethylsiloxane polymer liquid.

17. The photovoltaic module of claim 16, wherein the polydimethylsiloxane polymer liquid has the chemical formula (CH₃)₃SiO[SiO(CH₃)₂]_nSi(CH₃)₃, wherein n is a range of integers chosen such that the liquid has an average bulk viscosity that falls in the range between 40 centistokes and 60 centistokes.

18. The photovoltaic module of claim 1, wherein the filler material has a thermal coefficient of expansion of greater than 500×

10<sup>−

6</sup>/°

C.

19. The photovoltaic module of claim 1, wherein the filler material is formed from a silicone oil mixed with a dielectric gel.

20. The photovoltaic module of claim 19, wherein the silicone oil is a polydimethylsiloxane polymer liquid and the dielectric gel is a mixture of a first silicone elastomer and a second silicone elastomer.

21. The photovoltaic module of claim 1, wherein the filler material is formed from X %, by weight, a polydimethylsiloxane polymer liquid, Y %, by weight, a first silicone elastomer, and Z %, by weight, a second silicone elastomer, where X, Y, and Z sum to 100.

22. The photovoltaic module of claim 21, wherein the polydimethylsiloxane polymer liquid has the chemical formula (CH₃)₃SiO[SiO(CH₃)₂]_nSi(CH₃)₃, wherein n is a range of integers chosen such that the polymer liquid has an average bulk viscosity that falls in a range between 50 centistokes and 100,000 centistokes.

23. The photovoltaic module of claim 21, wherein the first silicone elastomer comprises at least sixty percent, by weight, dimethylvinyl-terminated dimethyl siloxane and between 3 and 7 percent by weight silicate.

24. The photovoltaic module of claim 21, wherein the second silicone elastomer comprises:

(i) at least sixty percent, by weight, dimethylvinyl-terminated dimethyl siloxane;

(ii) between ten and thirty percent by weight hydrogen-terminated dimethyl siloxane; and

(iii) between 3 and 7 percent by weight trimethylated silica.

25. The photovoltaic module of claim 21, wherein

X is between 30 and 90;

Y is between 2 and 20; and

Z is between 2 and 20.

26. The photovoltaic module of claim 1, further comprising a water resistant layer disposed on all or a portion of said transparent casing.

27. The photovoltaic module of claim 1, further comprising an antireflective coating disposed on all or a portion of said transparent casing.

28. The photovoltaic module of claim 1, wherein all or a portion of the elongated substrate is a rigid tube or a rigid solid rod.

29. The photovoltaic module of claim 1, wherein a solar cell in the one or more solar cells is cylindrical shaped and wherein

30. The photovoltaic module of claim 1, wherein the elongated substrate or the transparent casing is nonplanar.

31. The photovoltaic module of claim 1, wherein the elongated substrate or the transparent casing is characterized by a circular cross-section, an ovoid cross-section, a triangular cross-section, a pentangular cross-section, a hexagonal cross-section, a cross-section having at least one arcuate portion, or a cross-section having at least one curved portion.

32. The photovoltaic module of claim 1, wherein a first portion of the elongated substrate or the transparent casing is characterized by a first cross-sectional shape and a second portion of the elongated substrate or the transparent casing is characterized by a second cross-sectional shape.

33. The photovoltaic module of claim 32, wherein the first cross-sectional shape and the second cross-sectional shape are the same.

34. The photovoltaic module of claim 32, wherein the first cross-sectional shape and the second cross-sectional shape are different.

35. The photovoltaic module of claim 32, wherein at least ninety percent of a length of the elongated substrate is characterized by the first cross-sectional shape.

36. The photovoltaic module of claim 32, wherein the first cross-sectional shape is planar and the second cross-sectional shape has at least one arcuate side.

37. The photovoltaic module of claim 32, wherein a cross-section of the elongated substrate or the transparent casing forms an n-sided polygon, wherein n is an integer greater than or equal to 3.

38. The photovoltaic module of claim 1, wherein the portion of the elongated substrate that is rigid has a Young'"'"'s modulus of 20 GPa or greater.

39. The photovoltaic module of claim 1, wherein the portion of the elongated substrate that is rigid has a Young'"'"'s modulus of 40 GPa or greater.

40. The photovoltaic module of claim 1, wherein the portion of the elongated substrate that is rigid has a Young'"'"'s modulus of 70 GPa or greater.

41. The photovoltaic module of claim 1, wherein the portion of the elongated substrate that is rigid is made of a linear material.

42. The photovoltaic module of claim 1, wherein a longitudinal dimension of the elongated substrate is at least four times greater than the width dimension of the elongated substrate.

43. The photovoltaic module of any one of claim 1, wherein a longitudinal dimension of the elongated substrate is at least five times greater than the width dimension of the elongated substrate.

44. The photovoltaic module of claim 1, wherein the filler material has a viscosity of less than 1×

10⁶ cP.

45. The photovoltaic module of claim 1, wherein a longitudinal dimension of the elongated substrate is 50 cm or greater.

46. The photovoltaic module of claim 1, wherein the width dimension of the elongated substrate is 1 cm or greater.

47. The photovoltaic module of claim 1, wherein the width dimension of the elongated substrate is 5 cm or greater.

48. The photovoltaic module of claim 1, wherein the elongated substrate is either:

closed at a first end and a second end of the elongated substrate,

open at a first end and closed at a second end of the elongated substrate, or

open at a first end and a second end of the elongated substrate.

49. The photovoltaic module of claim 1, further comprising a first sealant cap that hermetically seals a first end of the transparent casing.

50. The photovoltaic module of claim 49, further comprising a second sealant cap that hermetically seals a second end of the transparent casing.

51. The photovoltaic module of claim 49, wherein the first sealant cap is made of metal, metal alloy, or glass.

52. The photovoltaic module of claim 49, wherein the first sealant cap is made of aluminosilicate glass, borosilicate glass, dichroic glass, germanium/semiconductor glass, glass ceramic, silicate/fused silica glass, soda lime glass, quartz glass, chalocogenide/sulphide glass, fluoride glass, PYREX glass, a glass-based phenolic, cereated glass, or flint glass.

53. The photovoltaic module of claim 49, wherein the first sealant cap is hermetically sealed to an inner surface or an outer surface of the transparent casing, and wherein the hermetic seal between the first sealant cap and the transparent casing is formed by a strip of sealant.

54. The photovoltaic module of claim 53, wherein the strip of sealant is on an inner edge of the first sealant cap, on an outer edge of the first sealant cap, on an outer edge of the transparent casing, or an inner edge of the transparent casing, and wherein the strip of sealant is formed from glass frit, sol-gel, or a ceramic cement.

55. The photovoltaic module of claim 50, wherein a water transmission rate of the photovoltaic module is 10⁻

4 g/m²·

day or less.

56. The photovoltaic module of claim 50, wherein a water transmission rate of the photovoltaic module is 10⁻

6 g/m²·

day or less.

57. The photovoltaic module of claim 50, wherein a water transmission rate of the photovoltaic module is 10⁻

7 g/m²·

day or less.

58. An assembly comprising a plurality of photovoltaic modules, each photovoltaic module in the plurality of photovoltaic modules having the structure of the photovoltaic module of claim 1, wherein photovoltaic modules in said plurality of solar photovoltaic modules are arranged in coplanar rows to form said assembly.

59. The assembly of claim 58, further comprising an albedo surface positioned to reflect sunlight into the plurality of photovoltaic modules.

60. The assembly of claim 59, wherein the albedo surface has an albedo that exceeds 80%.

61. The assembly of claim 59, wherein the albedo surface is Lambertian or diffuse.

62. The assembly of claim 59, wherein a first photovoltaic module and a second photovoltaic module in the plurality of photovoltaic modules are electrically coupled in series.

63. The assembly of claim 59, wherein a first photovoltaic module and a second photovoltaic module in the plurality of photovoltaic modules are electrically coupled in parallel.

64. The photovoltaic module of claim 1, wherein a back-electrode of a solar cell in the one or more solar cells is circumferentially disposed on the elongated substrate.

65. The photovoltaic module of claim 1, wherein a semiconductor junction of a first solar cell in the one or more solar cells is circumferentially disposed on the back-electrode of the first solar cell.

66. The photovoltaic module of claim 1, wherein a transparent conductive layer of a first solar cell in the one or more solar cells is circumferentially disposed on the semiconductor junction layer of the first solar cell.

67. The photovoltaic module of claim 1, wherein the one or more solar cells consists of three or more solar cells.

68. The photovoltaic module of claim 1, wherein the one or more solar cells consists of one hundred or more solar cells.

69. The photovoltaic module of claim 1, wherein one or more solar cells comprises a first solar cell and a second solar cell linearly arranged on said elongated substrate, and wherein the transparent conductive layer of the first solar cell is in serial electrical communication with the back-electrode of the second solar cell.

70. The photovoltaic module of claim 1, wherein the one or more solar cells consists of a plurality of solar cells and wherein:

a first terminal solar cell at a first end of said elongated substrate;

a second terminal solar cell at a second end of said elongated substrate; and

at least one intermediate photovoltaic cell between said first terminal solar cell and said second solar cell, wherein the transparent conductive layer of each intermediate solar cell in said at least one intermediate solar cell is in serial electrical communication with the back-electrode of an adjacent solar cell in said plurality of solar cells.

72. The photovoltaic module of claim 1, wherein said third refractive index is greater than the second refractive index.

73. The photovoltaic module of claim 1, wherein said third refractive index is smaller or equal in value to said second refractive index.

76. The photovoltaic module of claim 1, wherein a semiconductor junction of a first solar cell in the one or more solar cells comprises:

a first layer comprising a first inorganic semiconductor; and

a second layer comprising a second inorganic semiconductor.

77. The photovoltaic module of claim 76, wherein the first inorganic semiconductor and the second inorganic semiconductor are the same.

78. The photovoltaic module of claim 76, wherein the first inorganic semiconductor and the second inorganic semiconductor are the different.

79. The photovoltaic module of claim 76, wherein:

the first layer has a first conductivity type, and

the second layer has a second conductivity type that is different from the first conductivity type.

80. The photovoltaic module of claim 79, wherein a difference between the first conductivity type and the second conductivity type generates a potential difference across an interface between the first and second layers.

81. The photovoltaic module of claim 76, wherein the photovoltaic module is connected to an external load and wherein, responsive to light with photons having energies above a first band gap of the first layer, the first layer generates electrons that pass through the external load under an influence of the potential difference and then recombine with holes in the second layer.

82. The photovoltaic module of claim 81, wherein at least thirty percent of the electrons in the external load are derived from the first layer'"'"'s response to irradiation with photons above the first band gap.

83. The photovoltaic module of claim 81, wherein at least seventy percent of the electrons in the external load are derived from the first layer'"'"'s response to irradiation with photons above the first band gap.

84. The photovoltaic module of claim 79, wherein the first conductivity type is p and the second conductivity type is n.

85. The photovoltaic module of claim 79, wherein the first conductivity type is n and the second conductivity type is p.

86. The photovoltaic module of claim 76, further comprising a third layer disposed between the first and second layers, the third layer comprising an undoped insulator.

87. The photovoltaic module of claim 76, wherein:

the first inorganic semiconductor is an n type inorganic semiconductor; and

the second inorganic semiconductor is an n+ type inorganic semiconductor.

88. The photovoltaic module of claim 76, wherein

the first layer is an absorber layer;

and

the second layer is a junction partner layer.

89. The photovoltaic module of claim 76, wherein

the first layer is a junction partner layer;

and

the second layer is an absorption layer.

90. The photovoltaic module of claim 76, wherein:

the first layer is characterized by a first band gap;

the second layer is characterized by a second band gap; and

the second band gap is larger than the first band gap.

91. The photovoltaic module of claim 76, wherein:

the first layer is characterized by a first band gap;

the second layer is characterized by a second band gap; and

the second band gap is smaller than the first band gap.

92. The photovoltaic module of claim 76, wherein the first layer is characterized by a first band gap that is in the range of 0.7 eV to 2.2 eV.

93. The photovoltaic module of claim 76, wherein:

the first layer comprises copper-indium-gallium-diselenide (CIGS); and

the first layer is characterized by a first band gap that is in the range of 1.04 eV to 1.67 eV.

94. The photovoltaic module of claim 76, wherein:

the first layer comprises copper-indium-gallium-diselenide (CIGS); and

the first layer is characterized by a first band gap that is in the range of 1.1 eV to 1.2 eV.

95. The photovoltaic module of claim 76, wherein the first layer is an absorber layer that is graded such that a band gap of the first layer varies as a function of absorber layer depth.

96. The photovoltaic module of claim 76, wherein the first layer is an absorber layer comprising copper-indium-gallium-diselenide having the stoichiometry CuIn_1-xGa_xSe₂ with non-uniform Ga/In composition versus absorber layer depth.

97. The photovoltaic module of claim 76, wherein the first layer is an absorber layer comprising copper-indium-gallium-diselenide with the stoichiometry CuIn_1-xGa_xSe₂ and wherein a band gap of the absorber layer ranges between a first value in the range 1.04 eV to 1.67 eV and a second value in the range of 1.04 eV to 1.67 eV as a function of absorber layer depth, wherein the first value is greater than the second value.

98. The photovoltaic module of claim 76, wherein the first layer is an absorber layer comprising copper-indium-gallium-diselenide having the stoichiometry CuIn_1-xGa_xSe₂ wherein a band gap of the absorber layer ranges between a first value in the range of 1.04 eV to 1.67 eV to a second value in the range of 1.04 eV to 1.67 eV as a function of absorber layer depth, wherein the first value is less than the second value.

99. The photovoltaic module of claim 97, wherein the band gap of the absorber layer ranges between the first value and the second value in a continuous linear gradient as a function of absorber layer depth.

100. The photovoltaic module of claim 98, wherein the band gap of the absorber layer ranges between the first value and the second value in a continuous linear gradient as a function of absorber layer depth.

101. The photovoltaic module unit of claim 76, wherein the first layer is characterized by a first band gap that is in the range of 0.9 eV and 1.8 eV.

102. The photovoltaic module of claim 76, wherein the first layer is characterized by a first band gap that is in the range of 1.1 eV and 1.4 eV.

103. The photovoltaic module of claim 1, wherein the filler material is a gel.

104. The photovoltaic module of claim 1, wherein the filler material is a liquid.

105. The photovoltaic module of claim 1, wherein the filler material is a solid.

71. A photovoltaic module comprising

(A) a nonplanar elongated substrate having a first end and a second end;

and

(B) a plurality of solar cells linearly arranged on said nonplanar elongated substrate, the plurality of solar cells comprising a first solar cell and a second solar cell, each solar cell in said plurality of solar cells comprising;

(i) a back-electrode disposed on a surface of said nonplanar elongated substrate;

(ii) a semiconductor junction layer disposed on a surface of said back-electrode; and

(iii) a transparent conductive layer disposed on a surface of said semiconductor junction, wherein said transparent conductive layer has a first refractive index,

wherein the transparent conductive layer of the first solar cell in said plurality of solar cells is in serial electrical communication with the back-electrode of the second solar cell in said plurality of solar cells;

(C) a filler material disposed on the transparent conductive layer of each solar cell in the plurality of solar cells, wherein said filler material has a second refractive index that is smaller or equal in value to said first refractive index; and

(D) a transparent casing disposed on said filler material thereby sealing said photovoltaic module, wherein said transparent casing has a third refractive index.

74. The photovoltaic module of claim 71, wherein said third refractive index is greater than the second refractive index.

75. The photovoltaic module of claim 71, wherein said third refractive index is smaller or equal in value to said second refractive index.