Thin two sided single crystal solar cell and manufacturing process thereof
First Claim
1. A thin photovoltaic (PV) solar cell, comprising:
- A monocrystalline first film of silicon of a first conductivity type at a low doping concentration;
a second film of silicon of the first conductivity type at a medium concentration formed on the lower surface of said second film and epitaxial therewith, wherein the first film is formed by a diffusion process producing an exponential doping profile;
a third film of silicon of a second conductivity type other than the first conductivity type at a medium concentration epitaxial with the upper surface of the second film; and
a passivating film formed on the lower surface of the third film;
whereina multiplicity of openings are formed through the passivating film;
a conducting film is formed on the lower surface of the passivating film, wherein the conducting film fills said openings in the passivating film to make contact with the third film;
first contacts deposited on the lower surface of said conducting film; and
second contacts deposited on the upper surface of the third film.
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Accused Products
Abstract
A design and manufacturing method for a photovoltaic (PV) solar cell less than 100 μm thick are disclosed. A porous silicon layer is formed on a wafer substrate. Portions of the PV cell are then formed using diffusion, epitaxy and autodoping from the substrate. All front side processing of the solar cell (junctions, passivation layer, anti-reflective coating, contacts to the N+-type layer) is performed while the thin epitaxial layer is attached to the porous layer and substrate. The wafer is then clamped and exfoliated. The back side of the PV cell is completed from the region of the wafer near the exfoliation fracture layer, with subsequent removal of the porous layer, passivation, patterning of contacts, deposition of a conductive coating, and contacts to the P+-type layer. During manufacturing, the cell is always supported by either the bulk wafer or a wafer chuck, with no processing of bare thin PV cell
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Citations
37 Claims
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1. A thin photovoltaic (PV) solar cell, comprising:
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A monocrystalline first film of silicon of a first conductivity type at a low doping concentration; a second film of silicon of the first conductivity type at a medium concentration formed on the lower surface of said second film and epitaxial therewith, wherein the first film is formed by a diffusion process producing an exponential doping profile; a third film of silicon of a second conductivity type other than the first conductivity type at a medium concentration epitaxial with the upper surface of the second film; and a passivating film formed on the lower surface of the third film;
whereina multiplicity of openings are formed through the passivating film; a conducting film is formed on the lower surface of the passivating film, wherein the conducting film fills said openings in the passivating film to make contact with the third film; first contacts deposited on the lower surface of said conducting film; and second contacts deposited on the upper surface of the third film. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A thin photovoltaic (PV) solar cell, comprising
a monocrystalline first film of silicon of a first conductivity type at a low doping concentration; -
a second film of silicon of the first conductivity type at a medium concentration formed on the lower surface of the first film and epitaxial with the first film; a third film of silicon of a second conductivity type other than the first conductivity type at a medium concentration formed on the upper surface of the second film, epitaxial with the second film, and having a generally planar upper surface adjacent the second film and a textured lower surface; and a conformal anti-reflection coating deposited on the textured lower surface of the second film. a multiplicity of openings are formed through the anti-reflection coating; a conducting film formed on the lower surface of the anti-reflection coating, wherein the conducting film fills the said openings in the anti-reflection coating film to make contact with the third film; first contacts deposited on the lower surface of said conducting film; and second contacts deposited on the upper surface of the third film. - View Dependent Claims (13)
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14. A thin photovoltaic solar cell, comprising:
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a support; and a generally planar photovoltaic structure bonded to the support and including semiconductor silicon layers epitaxial with each other and including a P-N junction between the silicon layer and further including front side contacts on a side receiving radiation and back side contacts on the opposed sides, wherein the silicon layers have a total thickness of no more than 100 microns. - View Dependent Claims (15, 16, 17)
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18. A method for fabricating a photovoltaic solar cell on a thick wafer, comprising the steps of:
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a. forming a porous layer of silicon on the upper surface of a heavily doped silicon wafer of a first conductivity type b. epitaxially growing a moderately doped first layer of silicon of the first conductivity type on the upper surface of the porous silicon layer, wherein said epitaxial growth process induces the formation by autodoping of a moderately doped second layer of the first conductivity type in contact with the porous layer and within the first layer; and c. epitaxially growing a moderately doped third layer of silicon of a second conductivity type other than the first conductivity type on the upper surface of the second layer. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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Specification