Method for producing monocrystalline n-silicon solar cells, as well as a solar cell produced according to such a method

Abstract

A method for producing monocrystalline n-silicon solar cells having a rear-side passivated p + emitter and rear-side, spatially separate heavily doped n ++ -base regions near the surface, as well as an interdigitated rear-side contact finger structure, which is in conductive connection with the p + -emitter regions and the n ++ -base regions. An aluminum thin layer or an aluminum-containing thin layer is first deposited on the rear side of the n-silicon wafer, and the thin layer is subsequently structured so that openings are obtained in the region of the future base contacts. In a further process step, the aluminum is then diffused into the n-silicon wafer in order to form a structured emitter layer.

What is claimed is: 
     
         1 . A monocrystalline n-silicon solar cell, comprising:
 a deposited thin layer, formed of one of aluminum and an aluminum-containing material, on a rear-side of an n-silicon wafer, wherein the thin layer is structured so that openings in the region of future base doping are obtained; and   a structured emitter layer, which is formed by diffusing aluminum into the n-silicon wafer in a further process;   wherein the monocrystalline n-silicon solar cell includes:
 a p +  emitter on the rear-side of the n-silicon wafer; 
 heavily doped n ++ -base regions near the surface on the rear-side of the n-silicon wafer and spatially separate from the p +  emitter; and 
 an interdigitated rear-side contact finger structure, which is in conductive connection with the p + -emitter regions and the n ++ -base regions. 
   
     
     
         2 . The solar cell of  claim 1 , wherein the n ++  base regions on the rear side of the wafer have a lateral clearance from the p + -emitter, and wherein at least the n ++ -base regions have a concentration of the emitter doping material that is below the n-base concentration of the n-silicon wafer. 
     
     
         3 . The solar cell of  claim 1 , wherein:
 the n ++ -base regions are formed of base doping deposited in the openings, and the rear-side p +  emitter includes p +  emitter regions in which the openings that include the base doping are formed; and   the diffused aluminum is aluminum of the thin layer.   
     
     
         4 . The solar cell of  claim 3 , wherein the diffusion of the aluminum as emitter dopant and a diffusion of the doping material for the n ++ -base regions occurs in a common treatment operation. 
     
     
         5 . The solar cell of  claim 4 , wherein an insulaing layer is deposited over the the thin layer, and the doping material for the n ++ -base regions is deposited into the openings subsequent to the deposition of the insulating layer. 
     
     
         6 . The solar cell of  claim 4 , wherein the thin layer is deposited by one of a vapor deposit process and a sputter process. 
     
     
         7 . The solar cell of  claim 4 , wherein the structure of the deposited thin layer is in the form of strips by selective etching. 
     
     
         8 . The solar cell of  claim 7 , wherein the selective etching includes dry-etching with a metal shadow mask. 
     
     
         9 . The solar cell of  claim 7 , wherein the selective etching includes dry-etching with an organic mask. 
     
     
         10 . The solar cell of  claim 7 , wherein the selective etching is performed in a wet-chemical manner using an organic ink mask. 
     
     
         11 . The solar cell of  claim 7 , wherein the selective etching is performed by local printing of an etching paste. 
     
     
         12 . The solar cell of  claim 4 , wherein residue of the existing thin layer is removed once the aluminum diffusion has been completed. 
     
     
         13 . The solar cell of  claim 4 , wherein the structured emitter layer is covered by a dielectric protective layer across the full surface, and wherein the dielectric protective layer is opened up in the regions of the future base contacts. 
     
     
         14 . The solar cell of  claim 13 , wherein the openings are formed in regions of the future base doping, with the aid of an etching mask. 
     
     
         15 . The solar cell of  claim 14 , wherein the openings are formed via a strip-mask, and wherein the width of the produced openings are smaller than the width of the aluminum-free, strip-shaped regions in the wafer. 
     
     
         16 . The solar cell of  claim 13 , wherein the silicon wafer is subjected to texturation. 
     
     
         17 . The solar cell of  claim 1 , wherein:
 the diffused aluminum is aluminum of the thin layer;   the structured emitter layer is covered by a dielectric protective layer across the full surface;   the dielectric protective layer is opened up in the regions of the future base contacts; and   the silicon wafer is subjected to texturation that takes place on the front side of the wafer and in the region of the openings in the dielectric protective layer.   
     
     
         18 . The solar cell of  claim 17 , wherein material having a high phosphorus content is deposited in the region of the openings in the dielectric protective layer to produce the heavily doped n ++ -base regions as back surface field (BSF) regions located near the surface. 
     
     
         19 . The solar cell of  claim 18 , wherein the deposition is implemented by applying a paste using one of screen printing, stencil printing, and ink-jetting in local deposits. 
     
     
         20 . The solar cell of  claim 19 , wherein the deposited paste is subjected to a drying operation. 
     
     
         21 . The solar cell of  claim 18 , wherein the doping material for the n ++ -base regions is diffused in a thermal treatment operation. 
     
     
         22 . The solar cell of  claim 21 , wherein a further thermal treatment in a phosphorus-containing atmosphere, which includes POCl 3 , occurs to produce a flat phosphorus diffusion layer (FSF—front surface field) on the front side of the wafer featuring a layer resistance that is adjustable by the treatment temperature and the treatment time. 
     
     
         23 . The solar cell of  claim 1 , wherein:
 the diffused aluminum is aluminum of the thin layer; and   the p +  emitter and the n ++ -base regions are exposed by removal of the following via an etch bath: a residual doping material, a produced phosphorus silicate glass, residues of an insulation layer, and a produced AlSi eutecticum layer material.   
     
     
         24 . The solar cell of  claim 23 , wherein the wafer is covered by at least one passivation layer. 
     
     
         25 . The solar cell of  claim 24 , wherein the rear side of the wafer is locally freed of the passivation layer in the p + -emitter and n ++ -base regions to form local contact points. 
     
     
         26 . The solar cell of  claim 25 , wherein the entire rear side of the wafer is covered by a conductive layer, which includes an aluminum layer. 
     
     
         27 . The solar cell of  claim 26 , wherein the conductive layer is structured to form the interdigitated contact fingers. 
     
     
         28 . The solar cell of  claim 23 , wherein the diffusion of the aluminum as emitter dopant and diffusion of the doping material for the n ++ -base regions occurs in a common treatment operation.