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 interdigitated backside contact photovoltaic solar cell, comprising:
 a monocrystalline semiconducting principal layer of silicon of a first conductivity type having a textured first principal surface on a light receiving side of the solar cell and a planar second principal surface on an opposed side of the base layer;   a plurality of first finger structures formed on the second principal surface, extending along a first direction, spaced from each other along a perpendicular second direction, and each comprising   a heavily doped region of silicon of the first conductivity type formed in the principal layer, epitaxial therewith,   and being more heavily doped than the base layer, and   a first metal layer contacting the heavily doped region; and   a plurality of second finger structures formed on the second principal surface extending along the first direction, interdigitated with the first finger structures along the second direction, and each comprising   an opposed layer of a second conductivity type, formed on the principal layer, and epitaxial therewith to create a P-N junction with the base layer, and   a second metal layer contacting the opposed layer and electrically isolated from the first metal layer, wherein the first and second metal layers form two opposed leads for a load of the solar cell.   
     
     
         2 . The solar cell of  claim 1 , wherein the principal layer comprises a base layer and a surface layer which is adjacent the first principal surface, is thinner than the base layer, is textured, and is more heavily doped than the base layer. 
     
     
         3 . The solar cell of  claim 1 , further comprising a passivation and anti-reflection layer conformally formed on the textured first principal surface. 
     
     
         4 . The solar cell of  claim 1 , wherein the first conductivity type is P-type. 
     
     
         5 . The solar cell of  claim 1 , wherein the base layer and the opposed layer have a total thickness of less than 100 microns. 
     
     
         6 . The solar cell of  claim 5 , wherein the total thickness is no more than 50 microns. 
     
     
         7 . A backside contact photovoltaic (PV) solar cell, comprising:
 a monocrystalline first film of silicon of a first conductivity type;   a second film of silicon of the first conductivity type, formed on the upper surface of the first film, and epitaxial therein, wherein first film of silicon is formed by autodoping during epitaxial therewith;   a second film of silicon of a second conductivity type, formed in the lower surface of the first film, and epitaxial therewith; and   a first passivation film formed on the lower surface of the third film;   a plurality of first openings through third film and the first passivation film;   a plurality of contact regions formed in the lower surface of the first film, of the first conductivity type, more heavily doped than the first film, and aligned with the first openings;   a plurality of first electrical contacts formed to each of the contact regions; and   a plurality of second openings through the first passivation film and spaced between said first openings; and   a plurality of second electrical contacts to said third film formed through each of the second openings.   
     
     
         8 . The solar cell as in  claim 7 , further comprising a monocrystalline silicon wafer of the second conductivity type more heavily doped than the first film and having a porous surface layer on which the second film is disposed and epitaxial therewith. 
     
     
         9 . The solar cell as in  claim 8 , further comprising a passivation and anti-reflection layer conformally coated on the textured upper surface of the second film. 
     
     
         10 . The solar cell as in  claim 7 , wherein the first conductivity type is P-type. 
     
     
         11 . The solar cell as in  claim 7 , wherein the combined thickness of the first, second and third films and the passivation film is in the range 30 to 50 microns. 
     
     
         12 . The solar cell as in  claim 7 , wherein the combined thickness of the first, second and third films and the passivation film is in the range more than 50 to 100 microns. 
     
     
         13 . A method of fabricating a backside contact solar cell, comprising the steps of:
 a first deposition step of epitaxially growing a first film of silicon of a first conductivity type on a porous layer formed in silicon wafer;   a second deposition step of epitaxially growing a second film of silicon of a second conductivity type on the first film to thereby forming a P-N junction therebetween;   while the films are attached to the porous layer, a first forming step of forming first electrical contacts to the first layer and a second forming step of forming second electrical contacts to the second layer.   
     
     
         14 . The method of  claim 13 , wherein the wafer is of the first conductivity type more heavily doped than the first film and wherein the first deposition step causes autodoping to form a third film in the first film adjacent the porous layer which is more heavily doped than a remainder of the first film. 
     
     
         15 . The method of  claim 13 , further comprising the subsequent step of exfoliating the films from the wafer. 
     
     
         16 . A method for fabricating a thin interdigitated backside contact photovoltaic solar cell on a thick wafer, comprising the steps of:
 a. epitaxially growing a first layer of silicon of a first conductivity type on an upper surface of a porous crystalline silicon layer formed on a monocrystalline silicon substrate;   b. epitaxially growing a second layer of silicon on the upper surface of the first layer;   c. forming a first passivation layer on top of the second layer;   d. etching first openings through selected areas of the passivation and second layers;   e. forming contact regions within the second layer which are of the second conductivity type and more heavily doped than the second layer, wherein the dopant species to form the contact regions is diffused through the first openings;   f. etching second openings surrounding the first openings through the passivation and second layers   g. depositing a conducting layer   h. etching the conducting layer to remove portions not overlying the contact regions; and   i. etching second openings through the first passivation layer overlying central areas of the second layer.   
     
     
         17 . A thin photovoltaic solar cell, comprising:
 a monocrystalline semiconducting layer of silicon of a first conductivity type having a textured first surface on a light receiving side of the solar cell and a planar second surface on an opposed side;   a first plurality of metallization regions formed on the planar second surface, extending along a first direction, spaced from each other along a perpendicular second direction, and each comprising   a heavily doped region of silicon of the first conductivity type formed in the principal layer, epitaxial therewith,   and being more heavily doped than the monocrystalline semiconducting layer of silicon, and   a first metal layer contacting the heavily doped region; and   a second plurality of metallization regions formed on the planar second surface, extending along the first direction, interdigitated with the first finger structures along the second direction, and each comprising   an opposed layer of a second conductivity type, formed on the monocrystalline semiconducting layer of silicon, and epitaxial therewith to create a P-N junction with the monocrystalline semiconducting layer of silicon, and   a second metal layer contacting the opposed layer and electrically isolated from the first metal layer, wherein the first and second metal layers form contacts for the solar cell.   
     
     
         18 . A photovoltaic solar cell comprising:
 a monocrystalline first film of silicon of a first conductivity type;   a second epitaxial film of silicon of the first conductivity type formed on the upper surface of the first film, wherein the first film of silicon is in-situ doped during epitaxy;   a third epitaxial film of silicon of a second conductivity type, formed in the lower surface of the first film; and   a first passivation film formed on the lower surface of the third film;   a plurality of first openings through the third film and the first passivation film;   a plurality of contact regions formed in the lower surface of the first film, of the first conductivity type, more heavily doped than the first film, and aligned with the first openings;   a plurality of first electrical contacts formed to each of the contact regions; and   a plurality of second openings through the first passivation film and spaced between said first openings; and   a plurality of second electrical contacts to said third film formed through each of the second openings.   
     
     
         19 . A method for fabricating a solar cell, comprising the steps of:
 a first deposition step of epitaxially growing a first film of silicon of a first conductivity type on a porous layer formed on a silicon wafer;   a second deposition step of epitaxially growing a second film of silicon of a second conductivity type on the first film, thereby forming a P-N junction from said first film of silicon and said second film of silicon; and   while the films are attached to the porous layer, a first forming step of forming first electrical contacts to the first layer and a second forming step of forming second electrical contacts to the second layer.   
     
     
         20 . A method for fabricating a photovoltaic solar cell, comprising the steps of:
 a. epitaxially growing a first layer of silicon of a first conductivity type on an upper surface of a porous crystalline silicon layer formed on a monocrystalline silicon substrate;   b. epitaxially growing a second layer of silicon on the upper surface of the first layer;   c. forming a first passivation layer on top of the second layer;   d. etching first openings through selected areas of the passivation and second layers;   e. forming contact regions within the second layer which are of the second conductivity type and more heavily doped than the second layer, wherein the dopant species to form the contact regions is diffused through the first openings;   f. etching second openings surrounding the first openings through the passivation and second layers;   g. depositing a conducting layer;   h. etching the conducting layer to remove portions not overlying the contact regions; and   i. etching third openings through the first passivation layer overlying central areas of the second layer.