Solar cell and fabrication method thereof

Abstract

The present invention relates to a solar cell and a fabrication method thereof, whereby the method includes doping a silicon substrate having a first conductive type impurity with a second conductive type impurity, the second conductive type impurity being opposite to the first conductive type impurity, and thereby forming an emitter layer at a front surface part of the silicon substrate; forming an antireflection film on the emitter layer; forming a front electrode on the antireflection film; forming a rear electrode on a rear surface of the silicon substrate; and forming a back surface field layer at a rear surface part of the silicon substrate, the back surface field layer having a concentration of the first conductive type impurity that is higher than that of the silicon substrate, the back surface field layer having a different concentration of the second conductive type impurity from that of the emitter layer.

1 . A fabrication method of a solar cell, the method comprising:
 doping a silicon substrate having a first conductive type impurity with a second conductive type impurity, the second conductive type impurity being opposite to the first conductive type impurity, and thereby forming an emitter layer at a front surface part of the silicon substrate;   forming an antireflection film on the emitter layer;   forming a front electrode on the antireflection film;   forming a rear electrode on a rear surface of the silicon substrate; and   forming a back surface field layer at a rear surface part of the silicon substrate, the back surface field layer having a concentration of the first conductive type impurity that is higher than that of the silicon substrate, the back surface field layer having a different concentration of the second conductive type impurity from that of the emitter layer.   
     
     
         2 . The fabrication method of a solar cell according to  claim 1 , wherein the forming of the back surface field layer includes removing at least a portion of a second conductive type impurity doping layer formed at the rear surface part of the silicon substrate. 
     
     
         3 - 4 . (canceled) 
     
     
         5 . The fabrication method of a solar cell according to  claim 1 , wherein the forming of the front electrode and the rear electrode comprises coating a front electrode paste and a rear electrode paste, and annealing the front electrode paste and the rear electrode paste in temperatures from 600 to 750° C. at the same time. 
     
     
         6 . The fabrication method of a solar cell according to  claim 1 , further comprising texturing the silicon substrate to form an unevenness on a front surface or on the front surface and the rear surface of the silicon substrate. 
     
     
         7 . The fabrication method of a solar cell according to  claim 6 , wherein, when the unevenness is formed on the front surface and the rear surface, the forming of the back surface field layer includes reducing or removing the unevenness formed on the rear surface of the silicon substrate. 
     
     
         8 . The fabrication method of a solar cell according to  claim 2 , wherein the removing of the at least a portion of the second conductive type impurity doping layer comprises removing the second conductive type impurity doping layer and a portion of the silicon substrate at the rear surface part of the first conductive type silicon substrate. 
     
     
         9 . The fabrication method of a solar cell according to  claim 1 , wherein the forming of the emitter layer includes forming a first region where the second conductive type impurity has a first concentration and a second region where the second conductive type impurity has a concentration higher than the first concentration. 
     
     
         10 . The fabrication method of a solar cell according to  claim 9 , wherein the forming of the emitter layer further includes forming a mask layer on a front surface of the silicon substrate and forming a predetermined opening part in the mask layer;
 forming the second region through the predetermined opening part; and   forming the first region after removing the mask layer.   
     
     
         11 . The fabrication method of a solar cell according to  claim 10 , wherein the forming of the mask layer deposits a silicon oxide layer on the silicon substrate. 
     
     
         12 . (canceled) 
     
     
         13 . The fabrication method of a solar cell according to  claim 10 , wherein the forming of the predetermined opening part in the mask layer includes coating an etching paste on a predetermined region of the mask layer and etching the etching paste. 
     
     
         14 . (canceled) 
     
     
         15 . The fabrication method of a solar cell according to  claim 10 , wherein the forming of the second region and the first region comprises thermally diffusing different impurity doping concentrations of the second conductive type impurity in temperatures from 800 to 950° C. for 20 to 100 minutes. 
     
     
         16 . The fabrication method of a solar cell according to  claim 10 , wherein the forming of the second region includes thermally diffusing the second conductive type impurity at a higher temperature and for a longer time than when forming the first region. 
     
     
         17 - 18 . (canceled) 
     
     
         19 . A solar cell, comprising:
 a silicon substrate doped with a first conductive type impurity;   an emitter layer formed at a front surface part of the silicon substrate, the emitter layer having a second conductive type impurity opposite to the first conductive type impurity;   an antireflection film formed on the emitter layer;   a front electrode formed on the antireflection layer, and which penetrates through the antireflection film to contact the emitter layer;   a back surface field layer formed at a rear surface part of the silicon substrate, the back surface field layer being doped with a higher concentration of the first conductive type impurity than that of the silicon substrate, wherein the back surface field layer has a different concentration of the second conductive type impurity from that of the emitter layer; and   a rear electrode formed on the back surface field layer.   
     
     
         20 . (canceled) 
     
     
         21 . The solar cell according to  claim 19 , wherein the concentration of the second conductive type impurity in the back surface field layer is lower than the concentration of the second conductive type impurity in the emitter layer. 
     
     
         22 . The solar cell according to  claim 19 , wherein the concentration of the second conductive type impurity in the back surface field layer is approximately zero. 
     
     
         23 . (canceled) 
     
     
         24 . The solar cell according to  claim 19 , wherein the emitter layer has a first region where the second conductive type impurity has a first concentration and a second region where the second conductive type impurity has a concentration higher than the first concentration. 
     
     
         25 . The solar cell according to  claim 24 , wherein the first region has a shallower doped depth of the second conductive type impurity than that of the second region. 
     
     
         26 . The solar cell according to  claim 24 , wherein the front electrode contacts the second region of the emitter layer. 
     
     
         27 . (canceled) 
     
     
         28 . The solar cell according to  claim 19 , wherein a roughness of an unevenness formed on the rear surface of the substrate is different from a roughness of an unevenness formed on a front surface of the substrate. 
     
     
         29 . (canceled) 
     
     
         30 . The solar cell according to  claim 19 , wherein the second conductive type impurity includes at least one of phosphorous (P), arsenic (As) or antimony (Sb).