Solar cell, manufacturing method thereof and electrode material

Abstract

There is presented a solar cell comprising a semiconductor substrate of one conductivity-type, a layer of the opposite conductivity-type provided on a surface side of the semiconductor substrate, a surface electrode formed thereon, and a backside electrode formed on a backside of the semiconductor substrate, wherein the semiconductor substrate is formed with protrusions and recesses on the surface side thereof, and spaces that are filled with a glass component of an electrode material of the surface electrode are present in bottom portions of the recesses. This arrangement has eliminated a conventional problem in that silver in the electrode material gets into the bottom portions of the recesses and causes defects to be generated in the recesses due to stress generated during forming of the electrode.

1 . A solar cell comprising a semiconductor substrate of one conductivity-type, a layer of the opposite conductivity-type provided on a surface side of the semiconductor substrate, a surface electrode formed thereon, and a backside electrode formed on a backside of the semiconductor substrate, 
 wherein the semiconductor substrate is formed with microscopic protrusions and recesses on the surface side thereof, and spaces that are filled with a glass component of an electrode material of the surface electrode are present in bottom portions of the recesses.    
     
     
         2 . The solar cell according to  claim 1 , wherein the recesses have depths of 0.2 μm or more and 1 μm or less.  
     
     
         3 . The solar cell according to  claim 1 , wherein the spaces that are filled with the glass component of the electrode material of the surface electrode have depths of 0.2 μm or more and 0.8 μm or less.  
     
     
         4 . The solar cell according to  claim 1 , wherein the semiconductor substrate is a polycrystalline silicon substrate.  
     
     
         5 . A method of manufacturing a solar cell comprising the steps of: 
 forming microscopic protrusions and recesses on a surface side of a semiconductor substrate of one conductivity-type by dry etching method;    providing the surface side of the semiconductor substrate with an area of the opposite conductivity-type;    forming a surface electrode thereon; and    forming a backside electrode on a backside of the semiconductor substrate,    wherein an electrode material of the electrode comprises silver particles as a main component, and 5 or less weight parts have particle sizes of 0.1-1.0 μm per 100 weight parts of the silver.    
     
     
         6 . The method of manufacturing a solar cell according to  claim 5 , wherein the electrode material of the surface electrode formed on the surface side of the semiconductor substrate comprises silver particles having particle sizes of 0.1-5 μm as a main component.  
     
     
         7 . An electrode material for solar cell that is used in the manufacturing method of a solar cell according to  claim 5 , which comprises silver particles as a main component, wherein 5 or less weight parts per 100 weight parts of the silver have particle sizes of 0.1-1.0 μm.  
     
     
         8 . The electrode material for solar cell according to  claim 7 , which comprises silver particles having particle sizes of 0.1-5 μm as a main component.  
     
     
         9 . A solar cell comprising a semiconductor substrate of one conductivity-type formed with microscopic protrusions and recesses on a surface side thereof, an opposite conductivity-type layer provided on the surface side of the semiconductor substrate, an antireflective film and a surface electrode formed on the area of the opposite conductivity-type, and a backside electrode formed on a backside of the semiconductor substrate, 
 wherein the opposite conductivity-type layer includes an impurity of the opposite conductivity-type such that the sheet resistance of the surface side of the semiconductor substrate is 60-300 ohms/square, and    the surface electrode comprises silver as a main component and one or a plurality of metals selected from among Ti, Bi, Co, Zn, Zr, Fe and Cr or oxides thereof in an amount of 0.05-5 weight parts as metal per 100 weight parts of the silver.    
     
     
         10 . The solar cell according to  claim 9 , wherein the microscopic protrusions and recesses formed on the surface side of the semiconductor substrate have widths and heights of 2 μm or less, respectively.  
     
     
         11 . The solar cell according to  claim 9 , wherein the aspect ratio of the microscopic protrusions and recesses is 0.1-2.  
     
     
         12 . The solar cell according to  claim 9 , wherein the average particle size of the metal powder is 0.1-5 μm.  
     
     
         13 . The solar cell according to  claim 10 , wherein the antireflective film is a silicon nitride film, a silicon dioxide film or titanium dioxide film.  
     
     
         14 . A solar cell comprising a semiconductor substrate of one conductivity-type formed with microscopic protrusions and recesses on a surface side thereof, an opposite conductivity-type provided on the surface side of the semiconductor substrate, and an antireflective film of silicon nitride formed thereon, 
 wherein the etching rate is 350 Å/min or less when the antireflective film is etched by using a 32° C. aqueous solution in which the ratio of hydrofluoric acid containing 46% of hydrogen fluoride to water is 1:2.    
     
     
         15 . The solar cell according to  claim 14 , wherein the hydrogen concentration in the antireflective film is 1×10 22 -1×10 23  atoms/cm 3 .  
     
     
         16 . The solar cell according to  claim 14 , wherein the antireflective film has an index of refraction of 1.8-2.6 and a thickness of 50-1200 Å.  
     
     
         17 . The solar cell according to  claim 14 , wherein the microscopic protrusions and recesses have widths of 2 μm or less.  
     
     
         18 . The solar cell according to  claim 14 , wherein the microscopic protrusions and recesses have heights of 2 μm or less.  
     
     
         19 . The solar cell according to  claim 14 , wherein the aspect ratio of the microscopic protrusions and recesses is 0.1-2.  
     
     
         20 . The solar cell according to  claim 14 , wherein micro cracks are present in the recesses of the microscopic protrusions and recesses.  
     
     
         21 . The solar cell according to  claim 14 , wherein the sheet resistance of the surface of the semiconductor substrate is 60-300 ohms/square.  
     
     
         22 . The solar cell according to  claim 14 , wherein the semiconductor substrate comprises polycrystalline silicon.