Solar cell and method for manufacturing the same, and method for forming impurity region

Abstract

A Solar cell includes a substrate of a first conductive type; a first emitter portion positioned in the substrate and containing impurities of a second conductive type opposite the first conductive type; a second emitter portion positioned at the first emitter portion and containing impurities of the second conductive type, the second emitter portion having an impurity concentration higher than an impurity concentration of the first emitter portion; a first electrode connected to the second emitter portion; and a second electrode connected to the substrate, wherein the second emitter portion has a thickness equal to or less than a thickness of the first emitter portion.

1 . A solar cell, comprising:
 a substrate of a first conductive type;   a first emitter portion positioned in the substrate and containing impurities of a second conductive type opposite the first conductive type;   a second emitter portion positioned at the first emitter portion and containing impurities of the second conductive type, the second emitter portion having an impurity concentration higher than an impurity concentration of the first emitter portion;   a first electrode connected to the second emitter portion; and   a second electrode connected to the substrate,   wherein the second emitter portion has a thickness equal to or less than a thickness of the first emitter portion.   
     
     
         2 . The solar cell of  claim 1 , further comprising a back surface field portion positioned in the substrate and containing impurities of the first conductive type, the back surface field portion having an impurity concentration higher than an impurity concentration of the substrate. 
     
     
         3 . The solar cell of  claim 2 , wherein the first emitter portion, the second emitter portion and the back surface field portion are positioned on a same surface of the substrate. 
     
     
         4 . The solar cell of  claim 2 , wherein the first emitter portion and the second emitter portion are positioned on a first surface of the substrate, and the back surface field portion is positioned on a second surface of the substrate that is opposite the first surface. 
     
     
         5 . The solar cell of  claim 4 , wherein the back surface field portion is formed to cover most of the second surface of the substrate. 
     
     
         6 . The solar cell of  claim 1 , wherein the second emitter portion is at least one of a line type and a dot type. 
     
     
         7 . The solar cell of  claim 1 , wherein an impurity doped depth of the second emitter portion is equal to or less than an impurity doped depth of the first emitter portion. 
     
     
         8 . A solar cell, comprising:
 a substrate of a first conductive type;   a first back surface field portion positioned in the substrate and containing impurities of the first conductive type;   a second back surface field portion positioned at the first back surface field layer and containing impurities of the first conductive type, the second back surface field portion having an impurity concentration higher than an impurity concentration of the first back surface field portion;   an emitter region positioned in the substrate and containing impurities of a second conductive type opposite the first conductive type;   a first electrode connected to the emitter region; and   a second electrode connected to the second back surface field portion.   
     
     
         9 . The solar cell of  claim 8 , wherein the first back surface field portion, the second back surface field portion and the emitter portion are positioned on a same surface of the substrate. 
     
     
         10 . The solar cell of  claim 8 , wherein the first back surface field portion and the second back surface field portion are respectively at least one of a line type and a dot type. 
     
     
         11 . The solar cell of  claim 8 , wherein an impurity doped depth of the second back surface field portion is equal to or less than an impurity doped depth of the first back surface field portion. 
     
     
         12 . The solar cell of  claim 8 , wherein the second back surface field portion has a thickness equal to or less than a thickness of the first back surface field portion. 
     
     
         13 . The solar cell of  claim 8 , wherein the emitter region is at least one of a line type and a dot type. 
     
     
         14 . A solar cell, comprising:
 a substrate of a first conductive type;   a first back surface field portion positioned in the substrate and containing impurities of the first conductive type;   a second back surface field portion positioned at the first back surface field portion and containing impurities of the first conductive type, the second back surface field portion having an impurity concentration higher than an impurity concentration of the first back surface field portion;   a first emitter portion positioned in the substrate and having a second conductive type opposite the first conductive type;   a second emitter portion positioned at the first emitter layer and containing impurities of the second conductive type, the second emitter portion having an impurity concentration higher than an impurity concentration of the first emitter portion;   a first electrode connected to the second emitter portion; and   a second electrode connected to the second back surface field portion.   
     
     
         15 . The solar cell of  claim 14 , wherein the first back surface field portion, the second back surface field portion, the first emitter portion and the second emitter portion are positioned on a same surface of the substrate. 
     
     
         16 . The solar cell of  claim 14 , wherein the first back surface field portion, the second back surface field portion, the first emitter portion and the second emitter portion are respectively at least one of a line type and a dot type. 
     
     
         17 . The solar cell of  claim 14 , wherein an impurity doped depth of the second back surface field portion is equal to or less than an impurity doped depth of the first back surface field portion, and
 an impurity doped depth of the second emitter portion is equal to or less than an impurity doped depth of the first emitter portion.   
     
     
         18 . The solar cell of  claim 14 , wherein the second back surface field portion has a thickness equal to or less than a thickness of the first back surface field portion, and
 the second emitter portion has a thickness equal to or less than a thickness of the first emitter portion.   
     
     
         19 . The solar cell of  claim 14 , wherein the first electrode and the second electrode are coplanar.