Solar cell and fabricating method thereof

Abstract

Discussed herein are a solar cell and a fabricating method thereof. The solar cell includes a first conductivity-type semiconductor substrate, a second conductivity-type semiconductor layer formed on a front surface of the first conductivity-type semiconductor substrate, and having a conductivity opposite to that of the first conductivity-type semiconductor substrate, an anti-reflection film including at least one opening exposing a part of a surface of the second conductivity-type semiconductor layer, and formed on the second conductivity-type semiconductor layer, at least one front electrode contacting a part of the surface of the second conductivity-type semiconductor layer exposed through the at least one opening, and at least one rear electrode formed on a rear surface of the first conductivity-type semiconductor substrate, wherein the at least one front electrode includes a metal containing silver and lead-free glass frit.

What is claimed is: 
     
         1 . A solar cell, comprising:
 a first conductivity-type semiconductor substrate;   a second conductivity-type semiconductor layer formed on a front surface of the first conductivity-type semiconductor substrate, and having a conductivity opposite to that of the first conductivity-type semiconductor substrate;   an anti-reflection film including at least one opening exposing a part of a surface of the second conductivity-type semiconductor layer, and formed on the second conductivity-type semiconductor layer;   at least one front electrode contacting a part of the surface of the second conductivity-type semiconductor layer exposed through the at least one opening; and   at least one rear electrode formed on a rear surface of the first conductivity-type semiconductor substrate,   wherein the at least one front electrode includes a metal containing silver (Ag) and lead-free glass frit.   
     
     
         2 . The solar cell according to  claim 1 , wherein the at least one front electrode includes, with respect to a total wt % of metal components of the at least one front electrode, about 50˜85 wt % of silver (Ag) or an alloy containing silver (Ag), and about 0.2˜5 wt % of at least one metal selected from the group consisting of zinc (Zn), silicon (Si), aluminum (Al), copper (Cu), manganese (Mn), bismuth (Bi), phosphorus (P), boron (B), barium (Ba), and palladium (Pd). 
     
     
         3 . The solar cell according to  claim 1 , wherein the surface of the second conductivity-type semiconductor layer has an uneven structure including prominences and depressions, and the prominences and depressions in a region of the surface in which the at least one front electrode is formed are removed or have a smaller size than the prominences and depressions in other regions of the surface in which the at least one front electrode is not formed. 
     
     
         4 . The solar cell according to  claim 1 , wherein the first conductivity-type semiconductor substrate is a p-type silicon substrate doped with a p-type impurity. 
     
     
         5 . The solar cell according to  claim 1 , wherein:
 the second conductivity-type semiconductor layer is an n + -type emitter doped with an n-type impurity; and   the n + -type emitter has sheet resistance of 30˜100 Ω/square.   
     
     
         6 . The solar cell according to  claim 1 , wherein a thickness of the second conductivity-type semiconductor layer in a region of which that contacts the at least one front electrode is smaller than a thickness of the second conductivity-type semiconductor layer in regions of which that do not contact the at least one front electrode. 
     
     
         7 . The solar cell according to  claim 1 , wherein the anti-reflection film includes at least one selected from the group consisting of a silicon oxide film, a silicon oxynitride film, and a silicon nitride film. 
     
     
         8 . The solar cell according to  claim 1 , wherein the anti-reflection film includes at least one layer. 
     
     
         9 . The solar cell according to  claim 1 , wherein the at least one rear electrode includes at least one of aluminum (Al), silver (Ag), an aluminum silver (AgAl) alloy, and glass frit. 
     
     
         10 . The solar cell according to  claim 1 , wherein a back surface field (BSF) layer is formed at an interface between the rear surface of the first conductivity-type semiconductor substrate and the at least one rear electrode. 
     
     
         11 . The solar cell according to  claim 1 , further comprising a dielectric layer provided between the second conductivity-type semiconductor layer and the anti-reflection film, the dielectric layer having at least one opening located at the same position as the at least one opening of the anti-reflection film,
 wherein the at least one front electrode contacts the part of the surface of the second conductivity-type semiconductor layer through the at least one opening of the anti-reflection film and the at least one opening of the dielectric layer.   
     
     
         12 . The solar cell according to  claim 1 , further comprising a dielectric layer provided on the rear surface of the first conductivity-type semiconductor substrate,
 wherein the at least one rear electrode passes through a part of the dielectric layer and contacts a part of the rear surface of the first conductivity-type semiconductor substrate.   
     
     
         13 . A fabricating method of a solar cell, the method comprising:
 forming a second conductive-type semiconductor layer by doping a first conductivity-type semiconductor substrate with a second conductivity-type impurity having a conductivity opposite to that of the first conductivity-type semiconductor substrate;   forming an anti-reflection film on the second conductive-type semiconductor layer;   forming at least one opening exposing a part of a surface of the second conductive-type semiconductor layer by etching the anti-reflection film;   forming at least one front electrode contacting the part of the surface of the second conductivity-type semiconductor layer exposed through the at least one opening; and   forming at least one rear electrode formed on a rear surface of the first conductivity-type semiconductor substrate,   wherein the forming of the at least one front electrode is achieved by applying an electrode paste in the at least one opening using a screen printing method or a direct printing method and performing heat treatment, and the electrode paste includes a metal containing silver (Ag) or a metal alloy containing silver (Ag), lead-free glass frit, and a resin binding agent dispersed in an organic medium.   
     
     
         14 . The fabricating method according to  claim 13 , wherein the at least one opening is formed by patterning an etching paste on the anti-reflection film using the screen printing method or the direct printing method and then etching the anti-reflection film using the etching paste. 
     
     
         15 . The fabricating method according to  claim 13 , wherein the at least one opening is formed by patterning a mask layer on the anti-reflection film, etching the anti-reflection film in regions of which the mask layer is not formed, and then removing the mask layer. 
     
     
         16 . The fabricating method according to  claim 15 , wherein the mask layer is formed by patterning an etching prevention paste on the anti-reflection film using the screen printing method or the direct printing method. 
     
     
         17 . The fabricating method according to  claim 13 , wherein a temperature for performing the heat treatment is about 500˜850° C. 
     
     
         18 . The fabricating method according to  claim 13 , further comprising forming prominences and depressions on a front surface or the front and rear surfaces of the first conductivity-type semiconductor substrate by texturing the first conductivity-type semiconductor substrate. 
     
     
         19 . The fabricating method according to  claim 13 , wherein the formation of the at least one rear electrode includes forming a back surface field layer on the rear surface of the first conductivity-type semiconductor substrate by applying a rear electrode paste to the rear surface of the first conductivity-type semiconductor substrate and performing heat treatment. 
     
     
         20 . The fabricating method according to  claim 13 , wherein, prior to the forming of the at least one rear electrode, the method further comprises:
 forming a dielectric layer on the rear surface of the first conductivity-type semiconductor substrate; and   forming at least one opening, through which the at least one rear electrode contacts the rear surface of the first conductivity-type semiconductor substrate, through the dielectric layer.