Template for three-dimensional thin-film solar cell manufacturing and methods of use

Abstract

A template for three-dimensional thin-film solar cell substrate formation for use in three-dimensional thin-film solar cells. The template comprises a substrate which comprises a plurality of posts and a plurality of trenches between said plurality of posts. The template forms an environment for three-dimensional thin-film solar cell substrate formation.

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; wherein   a 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.   
     
     
         2 . The solar cell as in  claim 1 , wherein the PV solar cell includes the silicon layers which are epitaxial therebetween and include the first, second, and third films, and wherein the silicon layers, the passivating film and the conducting film have a total a thickness of no more than 100 microns. 
     
     
         3 . The solar cell as in  claim 1 , wherein the upper surface of the third film includes a generally planar lower surface and a textured upper surface to improve the light collection efficiency of the PV solar cell, and wherein the second contacts contact the textured upper surface. 
     
     
         4 . The solar cell as in  claim 3 , further comprising a passivation layer on the textured upper surface and wherein the second contacts penetrate the passivation layer and contact the third film. 
     
     
         5 . The solar cell as in  claim 4 , wherein said passivation layer is a silicon oxide layer. 
     
     
         6 . The solar cell as in  claim 4 , wherein said passivation layer is a layer of amorphous silicon. 
     
     
         7 . The solar cell as in  claim 4 , further comprising an anti-reflective coating on the upper surface of the passivation layer deposited before the deposition of the second contacts on the upper surface of the third film. 
     
     
         8 . The solar cell as in  claim 7 , wherein the anti-reflective coating comprises silicon nitride. 
     
     
         9 . The solar cell as in  claim 1 , wherein the combined thickness of the first, second and third films and the passivating film is in the range 30 to 50 microns. 
     
     
         10 . The solar cell as in  claim 1 , wherein the combined thickness of the first, second and third film and the passivating film is in the range 50 to 100 microns. 
     
     
         11 . The solar cell as in  claim 1 , wherein the first conductivity type is P type and the second conductivity type is N type. 
     
     
         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.   
     
     
         13 . The solar cell as in  claim 12 , wherein the PV solar cell includes silicon layers which are epitaxial therebetween and include the first, second, and third films, and wherein the silicon layers, the anti-reflection coating and the conducting film have a total a thickness of no more than 100 microns. 
     
     
         14 . A thin photovoltaic solar cell, comprising:
 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.   
     
     
         15 . The solar cell of  claim 14 , wherein the silicon adjacent the front side is textured on the front side thereof and planar on the backside thereof. 
     
     
         16 . A method for fabricating a photovoltaic solar cell on a thick wafer, comprising the steps of:
 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.   
     
     
         17 . A thin photovoltaic solar cell, comprising:
 a monocrystalline first film of silicon of a first conductivity type at a low doping concentration;   an epitaxial second film of silicon of the first conductivity type at a medium concentration formed on the lower surface of said first film, wherein the first film is formed by a diffusion process producing a graded doping profile;   an epitaxial 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; and   a passivating film formed on the lower surface of the third film; wherein   a 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.   
     
     
         18 . A thin photovoltaic solar cell, comprising
 a monocrystalline first film of silicon of a first conductivity type at a low doping concentration;   an epitaxial second film of silicon of the first conductivity type at a medium concentration formed on the lower surface of the first film;   an epitaxial 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 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 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 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.   
     
     
         19 . A thin photovoltaic solar cell, comprising:
 a support; and   a generally planar photovoltaic structure bonded to the support and including at least two epitaxial silicon layers, said at least two epitaxial silicon layers defining a P-N junction, and further including front side contacts on a side receiving radiation and back side contacts on an opposed side, wherein the silicon layers have a total thickness of no more than 100 microns.   
     
     
         20 . A method for fabricating a photovoltaic solar cell, said method comprising the steps of:
 a. forming a porous layer of silicon on an 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 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.