Composition for forming p-type diffusion layer, method for forming p-type diffusion layer, and method for producing photovoltaic cell

Abstract

The composition for forming a p-type diffusion layer in accordance with the present invention contains an acceptor element-containing glass powder and a dispersion medium. A p-type diffusion layer and a photovoltaic cell having a p-type diffusion layer are prepared by applying the composition for forming a p-type diffusion layer, followed by a thermal diffusion treatment.

1 . A composition for forming a p-type diffusion layer, comprising an acceptor element-containing glass powder and a dispersion medium. 
     
     
         2 . The composition for forming a p-type diffusion layer according to  claim 1 , wherein the acceptor element is at least one selected from boron (B), aluminum (Al) and gallium (Ga). 
     
     
         3 . The composition for forming a p-type diffusion layer according to  claim 1 , wherein the acceptor element-containing glass powder contains:
 at least one acceptor element-containing material selected from B 2 O 3 , Al 2 O 3  and Ga 2 O 3 ; and   at least one glass component material selected from SiO 2 , K 2 O, Na 2 O, Li 2 O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V 2 O 5 , SnO, ZrO 2  and MoO 3 .   
     
     
         4 . A method for forming a p-type diffusion layer, including:
 applying, on a semiconductor substrate, the composition for forming a p-type diffusion layer of  claim 1 ; and   conducting a thermal diffusion treatment.   
     
     
         5 . A paste composition for forming a p-type diffusion region in a semiconductor substrate, comprising a dispersion of acceptor element-containing glass particles in a spreadable paste medium. 
     
     
         6 . A method for producing a photovoltaic cell, including:
 applying, on a semiconductor substrate, the composition for forming a p-type diffusion layer of  claim 1 ;   subjecting the substrate to a thermal diffusion treatment to form a p-type diffusion layer; and   forming an electrode on the p-type diffusion layer.   
     
     
         7 . The method for producing a photovoltaic cell according to  claim 6 , comprising the steps of applying the composition for forming an p-type diffusion layer to the silicon substrate, optionally through an n-type diffusion layer, and heat treatment to form a glass layer and an p + -type diffusion layer beneath the glass layer. 
     
     
         8 . The method for producing a photovoltaic cell according to  claim 6 , comprising the following steps:
 (x) removing the damaged surface layer from a crystalline silicon substrate;   (xi) etching the crystalline silicon substrate to form a textured front surface structure;   (xii) forming an n-type diffusion layer around the silicon substrate in a mixed gas atmosphere of phosphorus oxychloride, nitrogen and oxygen, and removing the n-type diffusion layer from the side faces by side etching;   (xiii) applying the composition for forming an p-type diffusion layer to the n-type diffusion layer on the rear surface of the silicon substrate, and after optional drying to remove solvent present in the composition, heat treatment, preferably at a temperature of 600 to 1200° C., to form a glass layer and an p + -type diffusion layer beneath the glass layer;   (xiv) removing the glass layer by etching;   (xv) forming an antireflective film over the n-type diffusion layer on the front surface;   (xvi) forming surface electrode on the antireflective film;   (xvii) forming rear surface electrode on the p + -type diffusion layer; and   (xviii) sintering to establish electrical connection between the surface electrode and the silicon substrate.   
     
     
         9 . The method for producing a photovoltaic cell according to  claim 6  comprising the following steps:
 (xii) removing the damaged surface layer from a crystalline silicon substrate; 
 (xiii) etching the crystalline silicon substrate to form a textured surface structure; 
 (xiv) applying a composition comprising a donor-element containing glass powder and a dispersion medium on the textured front surface; 
 (xv) applying the composition for forming an p-type diffusion layer to the rear surface of the silicon substrate; 
 (xvi) optional drying to remove solvent present in the compositions applied to the surfaces of the silicon substrate; 
 (xvii) heat treatment, preferably at a temperature of 600 to 1200° C., to form a glass layer and an n-type diffusion layer beneath the glass layer on the front surface, and a glass layer and an p + -type diffusion layer beneath the glass layer on the rear surface; 
 (xviii) removing the glass layers by etching; 
 (xix) forming an antireflective film over the n-type diffusion layer on the front surface; 
 (xx) forming surface electrode on the antireflective film; 
 (xxi) forming rear surface electrode on the p + -type diffusion layer on the rear surface; and 
 (xxii) sintering to establish electrical connection between the surface electrode and the silicon substrate. 
 
     
     
         10 . A method for forming a p-type diffusion region in a semiconductor, comprising the steps of:
 1) coating a portion of a semiconductor substrate with a layer of a composition comprising a dispersion of acceptor element-containing glass particles in a dispersion medium; and   2) heating the coated semiconductor substrate to a temperature sufficient to cause acceptor element diffusion from the glass into the semiconductor substrate so as to form an p-type diffusion region in the semiconductor substrate.   
     
     
         11 . A use of an acceptor element-containing glass powder for forming a p-type diffusion layer on a semiconductor substrate. 
     
     
         12 . The use according to  claim 11 , wherein the acceptor element is at least one selected from boron (B), aluminum (Al) and gallium (Ga). 
     
     
         13 . The use according to  claim 11 , wherein the acceptor element-containing glass powder contains:
 at least one acceptor element-containing material selected from B 2 O 3 , Al 2 O 3  and Ga 2 O 3 ; and   at least one glass component material selected from SiO 2 , K 2 O, Na 2 O, Li 2 O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V 2 O 5 , SnO, ZrO 2  and MoO 3 .   
     
     
         14 . The use according to  claim 11 , wherein the acceptor element-containing glass powder is used in the form of a composition, which further comprises a dispersion medium. 
     
     
         15 . The use according to  claim 14 , wherein the dispersion medium comprises a binder and a solvent. 
     
     
         16 . The use according to  claim 15 , wherein the binder is a cellulose derivative, in particular ethylcellulose, and/or the solvent is an ester.