Method for producing photovoltaic cell

Abstract

In a method for producing a photovoltaic cell, the improvement comprising: 1) coating a portion of a semiconductor substrate with a layer of a composition comprising acceptor element-containing glass particles and a dispersion medium, and 2) heating the coated semiconductor substrate to a temperature sufficient to cause acceptor element diffusion from the glass particles into the semiconductor substrate so as to form an p-type diffusion region in the semiconductor substrate.

1 . In a method for producing a photovoltaic cell, the improvement comprising:
 1) coating a portion of a semiconductor substrate with a layer of a composition comprising acceptor element-containing glass particles and a dispersion medium, and   2) heating the coated semiconductor substrate to a temperature sufficient to cause acceptor element diffusion from the glass particles into the semiconductor substrate so as to form an p-type diffusion region in the semiconductor substrate.   
     
     
         2 . The improvement of  claim 1 , wherein the layer of the composition is dried before step 2). 
     
     
         3 . The improvement of  claim 2 , wherein the drying is conducted at a temperature in a range of about 80° C. to about 300° C. 
     
     
         4 . The improvement of  claim 1 , wherein the heating in step 2) is conducted at a temperature in a range of about 600° C. to about 1200° C. 
     
     
         5 . The improvement of  claim 1 , wherein the heating in step 2) is conducted for a period of time in a range from about one minute to about 60 minutes. 
     
     
         6 . The improvement of  claim 5 , wherein the heating in step 2) is conducted for a period of time in a range from about 2 minutes to about 30 minutes. 
     
     
         7 . The improvement of  claim 1 , wherein the semiconductor substrate is silicon. 
     
     
         8 . The improvement of  claim 1 , wherein a glass layer formed on the surface of the semiconductor substrate in step 2) is subsequently removed. 
     
     
         9 . The improvement of  claim 8 , wherein the glass layer formed on the surface of the semiconductor substrate in step 2) is removed by etching. 
     
     
         10 . The improvement of  claim 1 , wherein the glass particles contain an acceptor element selected from the group consisting of B (boron), aluminum (Al) and gallium (Ga). 
     
     
         11 . The improvement of  claim 1 , wherein the glass particles have a glass composition comprising:
 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 .   
     
     
         12 . The improvement of  claim 11 , wherein the glass composition contains from about 0.1% to about 95%, by mass, of the glass-forming compound. 
     
     
         13 . The improvement of  claim 12 , wherein the glass composition contains from about 0.5% to about 90%, by mass, of the glass-forming compound. 
     
     
         14 . The improvement of  claim 11 , wherein the glass composition contains not more than about 50%, by mass, of V 2 O 5 . 
     
     
         15 . The improvement of  claim 14 , wherein the glass composition contains from about 1% to about 50%, by mass, of V 2 O 5 . 
     
     
         16 . The improvement of  claim 15 , wherein the glass composition contains from about 3% to about 40%, by mass, of V 2 O 5 . 
     
     
         17 . The improvement of  claim 11 , wherein the glass composition is substantially devoid of V 2 O 5 . 
     
     
         18 . The improvement of  claim 1 , wherein the glass particles have a softening temperature in a range from about 200° C. to about 1000° C. 
     
     
         19 . The improvement of  claim 1 , wherein the glass particles have a softening temperature in a range from about 300° C. to about 900° C. 
     
     
         20 . The improvement of  claim 1 , wherein the glass particles have a particle diameter not greater than about 100 micrometers. 
     
     
         21 . The improvement of  claim 1 , wherein the glass particles have a particle diameter not greater than about 50 micrometers. 
     
     
         22 . The improvement of  claim 1 , wherein the spreadable paste medium comprises a binder and a solvent for the binder. 
     
     
         23 . The improvement of  claim 22 , wherein the binder comprises at least one natural or synthetic organic polymer. 
     
     
         24 . The improvement of  claim 22 , wherein the binder comprises ethylcellulose. 
     
     
         25 . The improvement of  claim 22 , wherein the solvent is a solvent volatile in a temperature range from about 80° C. to about 300° C. 
     
     
         26 . The improvement of  claim 1 , wherein the glass particles constitute from about 0.1%, by mass, to about 95%, by mass, of the paste composition. 
     
     
         27 . The improvement of  claim 1 , wherein the glass particles constitute from about 1%, by mass, to about 90%, by mass, of the paste composition. 
     
     
         28 . The improvement of  claim 1 , further comprising particles of a metal capable of promoting crystallization of the glass. 
     
     
         29 . The improvement of  claim 28 , wherein the metal is selected from the group consisting of silver, silicon, copper, iron, zinc, and manganese. 
     
     
         30 . The improvement of  claim 29 , wherein the metal is selected from the group consisting of silver, silicon, and zinc.