Hybrid window layer for photovoltaic cells

• US 20080000524A1
• Filed: 09/07/2007
• Published: 01/03/2008
• Est. Priority Date: 10/29/2003
• Status: Active Grant

• Current Assignee: University of Toledo
• Original Assignee: University of Toledo
• Inventors: Deng, Xunming
• Granted Patent: US 8,030,120 B2
• Time in Patent Office: Days
• US Class Current: 136/255
• CPC Class Codes: H01L 31/03762 including only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/03765 including AIVBIV compounds or alloys, e.g. SiGe, SiC
• CPC Class Codes: H01L 31/03921 including only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/056 the light-reflecting means being of the back surface reflector [BSR] type
• CPC Class Codes: H01L 31/0745 comprising a AIVBIV heterojunction, e.g. Si/Ge, SiGe/Si or Si/SiC solar cells
• CPC Class Codes: H01L 31/202 including only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/204 including AIVBIV alloys, e.g. SiGe, SiC
• CPC Class Codes: Y02E 10/52 PV systems with concentrators
• CPC Class Codes: Y02E 10/548 Amorphous silicon PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

A novel photovoltaic solar cell and method of making the same are disclosed. The solar cell includes: at least one absorber layer which could either be a lightly doped layer or an undoped layer, and at least a doped window-layers which comprise at least two sub-window-layers. The first sub-window-layer, which is next to the absorber-layer, is deposited to form desirable junction with the absorber-layer. The second sub-window-layer, which is next to the first sub-window-layer, but not in direct contact with the absorber-layer, is deposited in order to have transmission higher than the first-sub-window-layer.

Claims

1-30. -30. (canceled)

31. A novel photovoltaic solar cell comprising:

at least one n-type layer,

at least one i-type layer, and

at least two sub-p-layers, wherein first sub-p-layer is deposited at a desired first temperature on the i-type layer, and

a second sub-p-layer is deposited on the first sub-p-layer at a desired second temperature which is lower than the first temperature at which the first sub-p-layer is deposited.

32. The solar cell of claim 31, wherein the first sub-p-layer is deposited on the i-type layer at a temperature sufficiently high to form a good junction with the i-layer.

33. The solar cell of claim 32, wherein the first sub-p-layer is deposited at about 140°

C.

34. The solar cell of claim 31, wherein the second sub-p-layer has a transparency greater than the transparency of the first sub-p-layer.

35. The solar cell of claim 34, wherein the second sub-p-layer is deposited at a temperature sufficient low to provide acceptable transparency.

36. The solar cell of claim 35, wherein the second sub-p-layer is deposited at or below a temperature of about 70°

C.

37. The solar cell of claim 31, wherein the first sub-p-layer has a thickness in the range of about 1 nm to about 4 nm and the second sub-p-layer has a temperature in the range of about 5 nm to about 20 nm.

38. The solar cell of claim 31, wherein the first sub-p-layer is thinner than the second sub-p-layer.

39. The solar cell of claim 31, having a conversion efficiency of about 10% or greater.

40. The solar cell of claim 31, further comprising a substrate such as a glass, metal or plastic.

41. The solar cell of claim 40, further comprising a suitable transparent conductive oxide layer adjacent the second sub-p-layer.

42. The solar cell of claim 41, wherein the transparent conductive oxide layer comprises indium-tin-oxide (ITO) deposited at a temperature sufficiently low to avoid damaging the sub-p-layers.

43. The solar cell of claim 31, further comprising an encapsulation layer overlaying the cell to provide a substantially airtight and watertight protective barrier against moisture and contaminants.

44. The solar cell of claim 31, further comprising a buffer semi-conductor layer between the n-layer and the i-layer and between the i-layer and the first sub-p-layer.

45. The solar cell of claim 31, wherein the first and second layers comprise an amorphous silicon-containing material.

46. The solar cell of claim 45, wherein the i-layer comprises amorphous silicon germanium.

47. The solar cell of claim 46, wherein the n-layer comprises amorphous silicon.

48. A method for manufacturing a solar cell comprising the steps of

(i) providing a substrate;

(ii) depositing a layer of n-type semi-conductor on the substrate at a temperature sufficiently low to avoid damage or melting the substrate;

(iii) depositing an i-layer on the n-layer at a temperature sufficiently low to avoid melting or damaging the n-layer;

(iv) depositing a first sub-p-layer on the i-layer at a temperature sufficiently high to form a good junction with the i-layer; and

(v) depositing a second sub-p-layer on the first sub-p-layer at a temperature lower than the first temperature at which the first sub-p-layer is deposited.

49. The method of claim 48, further including depositing a layer of a transparent conductive oxide on the second p-layer.

50. The method of claim 49, wherein a current collection layer is deposited onto the substrate prior to deposition of the n-layer onto the substrate.

51. The method of claim 48, wherein during the i-layer deposition an optimized GeH₄ to Si₂H₆ ratio provides a Ge content suitable for forming a high efficiency single-junction solar cell.

52. The method of claim 51, wherein an optimized level of hydrogen dilution is used to form the i-layer.

53. The method of claim 52, wherein the substrate comprises glass or metal including aluminum, bismuth, iron, niobium, titanium or steel.

54. The method of claim 48, wherein the first and second sub-p-layers are deposited by a chemical vapor deposition process.

55. The method of claim 54, wherein the chemical vapor deposition process comprises plasma enhanced chemical vapor deposition.

56. The method of claim 55, in which the plasma enhanced chemical vapor deposition comprises radio frequency plasma enhanced chemical vapor deposition.

57. The method of claim 56, wherein the first and second p-layers amorphous silicon-containing material selected from the group consisting of hydrogenated amorphous silicon, hydrogenated amorphous carbon, and hydrogenated amorphous silicon germanium.

58. The method of claim 57, wherein the i-layer comprises hydrogenated amorphous silicon germanium having a bandgap ranging from about 1.4 e-V to 1.6 e-V and wherein the first and second sub p-layers comprise amorphous silicon with a bandgap of 1.4 e-V.

59. The method of claim 58, wherein the plasma enhanced chemical vapor deposition is by at least one of the following:

cathodic direct current glow discharge, anodic direct current glow discharge, radio frequency glow discharge, very high frequency (VHF) glow discharge, alternate current glow discharge, or microwave glow discharge at a pressure ranging from about 0.5 to about 5 TORR with a dilution ratio of dilutant to feedstock (deposition gas) ranging from about 5;

1 to about 200;

1.

60-74. -74. (canceled)