Paste and manufacturing method of solar cell using the same

Abstract

Disclosed are a paste and a method for manufacturing a solar cell through screen printing said paste. The paste contains inorganic powder; an organic solvent; and a binder, and the inorganic powder has a tap density of 0.01 to 20 g/cm 3 . An etching mask pattern formed using said paste has good etch resistance in an etch-back process by which a selective emitter is formed, and thus, a stable emitter can be formed.

1 . A paste for forming an etching mask pattern, comprising:
 inorganic powder;   an organic solvent; and   a binder,   wherein the inorganic powder has a tap density of 0.01 to 20 g/cm 3 .   
     
     
         2 . The paste for forming an etching mask pattern according to  claim 1 ,
 wherein the binder includes an organic solvent and a binder resin.   
     
     
         3 . The paste for forming an etching mask pattern according to  claim 1 ,
 wherein the inorganic powder includes metal or metal oxide powder, or mixtures thereof.   
     
     
         4 . The paste for forming an etching mask pattern according to  claim 1 ,
 wherein the inorganic powder includes any one metal or metal oxide powder selected from the group consisting of Si, Ti, ITO, SiO 2 , TiO 2 , Bi 2 O 3  and PbO, or mixtures thereof.   
     
     
         5 . The paste for forming an etching mask pattern according to  claim 1 ,
 wherein the inorganic powder has an average particle diameter of 1 nm to 10 μm.   
     
     
         6 . The paste for forming an etching mask pattern according to  claim 1 ,
 wherein the inorganic powder has an average particle diameter of 10 nm to 5 μm.   
     
     
         7 . The paste for forming an etching mask pattern according to  claim 1 ,
 wherein the inorganic powder is coated with silane compound, silicon oil or fatty acid.   
     
     
         8 . A method for manufacturing a solar cell, comprising:
 (a) preparing a silicon semiconductor substrate doped with a first conductive impurity;   (b) forming an emitter layer on the substrate by doping an upper portion of the substrate with a second conductive impurity having the opposite polarity to the first conductive impurity;   (c) forming an etching mask pattern at a front electrode connection area on the emitter layer using a paste comprising inorganic powder having a tap density of 0.01 to 20 g/cm 3 , an organic solvent and a binder;   (d) etching back the emitter layer by using the etching mask pattern as a mask;   (e) removing the etching mask pattern remaining after the etch-back;   (f) forming an anti-reflection film over a front surface of the substrate;   (g) establishing a connection between a front electrode and the front electrode connection area by penetrating through the anti-reflection film; and   (h) establishing a connection between a rear electrode and a rear surface of the substrate.   
     
     
         9 . The method for manufacturing a solar cell according to  claim 8 ,
 wherein the binder includes an organic solvent and a binder resin.   
     
     
         10 . The method for manufacturing a solar cell according to  claim 8 ,
 wherein the first conductive impurity is a p-type impurity and the second conductive impurity is an n-type impurity.   
     
     
         11 . The method for manufacturing a solar cell according to  claim 8 ,
 wherein the inorganic powder includes metal or metal oxide powder, or mixtures thereof.   
     
     
         12 . The method for manufacturing a solar cell according to  claim 8 ,
 wherein the inorganic powder of step (c) includes any one metal or metal oxide powder selected from the group consisting of Si, Ti, ITO, SiO 2 , TiO 2 , Bi 2 O 3  and PbO, or mixtures thereof.   
     
     
         13 . The method for manufacturing a solar cell according to  claim 8 ,
 wherein the inorganic powder has an average particle diameter of 1 nm to 10 μm.   
     
     
         14 . The method for manufacturing a solar cell according to  claim 8 ,
 wherein the inorganic powder has an average particle diameter of 10 nm to 5 μm.   
     
     
         15 . The method for manufacturing a solar cell according to  claim 8 ,
 wherein the inorganic powder is coated with silane compound, silicon oil or fatty acid.   
     
     
         16 . The method for manufacturing a solar cell according to  claim 8 ,
 wherein, in the step (d), the emitter layer is etched back using a selective wet etchant in which HNO 3 , HF, CH 3 COOH and H 2 O are mixed at a volume ratio of 10:0.1˜0.01:1˜3:5˜10.   
     
     
         17 . The method for manufacturing a solar cell according to  claim 16 ,
 wherein the selective wet etchant has an etch rate of 0.08 to 0.12 μm/sec for an area doped with a high concentration of impurity in the emitter layer and an etch rate of 0.01 to 0.03 μm/sec for an area doped with a low concentration of impurity in the emitter layer.   
     
     
         18 . The method for manufacturing a solar cell according to  claim 8 ,
 wherein, in the step (d), the emitter layer is etched back using an alkaline wet etchant or a plasma dry etchant.