Solar cell

Abstract

A solar cell includes a substrate of a first conductive type, a plurality of first electrodes which are positioned on one surface of the substrate and extending in a first direction, an emitter region which is electrically connected to the first electrodes and is of a second conductive type opposite the first conductive type, a plurality of second electrodes which are positioned on another surface of the substrate and extending in the first direction, and a back surface field region including a plurality of first field regions which are locally formed at locations corresponding to the second electrodes in the same direction as the second electrodes and are electrically connected to the second electrodes. A distance between adjacent first field regions is less than a distance between adjacent second electrodes.

What is claimed is: 
     
         1 . A solar cell comprising:
 a substrate of a first conductive type;   a plurality of first electrodes which are positioned on one surface of the substrate and extending in a first direction;   an emitter region which is electrically connected to the plurality of first electrodes and is of a second conductive type opposite the first conductive type;   a plurality of second electrodes which are positioned on another surface of the substrate and extending in the first direction; and   a back surface field region including a plurality of first field regions which are locally formed at locations corresponding to the plurality of second electrodes in the same direction as the plurality of second electrodes and are electrically connected to the plurality of second electrodes,   wherein a distance between adjacent first field regions in a second direction perpendicular to the first direction is less than a distance between adjacent second electrodes in the second direction.   
     
     
         2 . The solar cell of  claim 1 , wherein the distance between the adjacent second electrodes is less than the distance between the adjacent first electrodes within a range of about 1.0 mm to 2.5 mm. 
     
     
         3 . The solar cell of  claim 1 , wherein a surface concentration of the back surface field region is about 1E19/cm 2  to 5E20/cm 2 . 
     
     
         4 . The solar cell of  claim 1 , wherein a junction depth of the back surface field region is about 0.3 μm to 1.8 μm. 
     
     
         5 . The solar cell of  claim 1 , wherein one first field region includes a first region which directly contacts one second electrode and overlaps the one second electrode, and a second region which is positioned around the first region in the second direction and does not overlap the one second electrode,
 wherein a line width of the one first field region is about two times to 4.5 times a line width of the one second electrode.   
     
     
         6 . The solar cell of  claim 5 , wherein the line width of the one second electrode is about 50 μm to 150 μm, and the line width of the one first field region is about 100 μm to 600 μm. 
     
     
         7 . The solar cell of  claim 5 , wherein the one second region is positioned on one side or both sides of the one first region in the second direction. 
     
     
         8 . The solar cell of  claim 5 , further comprising at least one second current collector which is electrically connected to the plurality of second electrodes and extends in the second direction,
 wherein a portion of the one first field region overlaps a portion of the at least one second current collector.   
     
     
         9 . The solar cell of  claim 5 , further comprising at least one second current collector which is electrically connected to the plurality of second electrodes and extends in the second direction,
 wherein the back surface field region further includes a second field region including a third region which directly contacts the second current collector and overlaps the second current collector, and a fourth region which is positioned around the third region and does not overlap the second current collector.   
     
     
         10 . The solar cell of  claim 9 , wherein a line width of the second field region is greater than a line width of the second current collector, and equal to or less than about 1.5 times the line width of the second current collector. 
     
     
         11 . The solar cell of  claim 9 , wherein a line width of the second field region is about 1.6 mm to 2.0 mm. 
     
     
         12 . The solar cell of  claim 9 , wherein the fourth region is positioned on one side or both sides of the third region in the first direction. 
     
     
         13 . The solar cell of  claim 5 , further comprising:
 a first passivation layer positioned on a front surface of the emitter region, on which the plurality of first electrodes are not positioned; and   a second passivation layer positioned on a back surface of the substrate, on which the plurality of second electrodes are not positioned,   wherein the first passivation layer and the second passivation layer are formed of a material having fixed charges of the first conductive type.   
     
     
         14 . The solar cell of  claim 13 , wherein the first passivation layer and the second passivation layer each contains aluminum oxide (AlO x ) or yttrium oxide (Y 2 O 3 ) having negative fixed charges. 
     
     
         15 . The solar cell of  claim 14 , wherein the first passivation layer and the second passivation layer each have a refractive index of about 1.55 to 1.7 and a thickness of about 5 nm to 30 nm. 
     
     
         16 . The solar cell of  claim 14 , further comprising a first anti-reflection layer positioned on the first passivation layer and a second anti-reflection layer positioned on a back surface of the second passivation layer,
 wherein the first anti-reflection layer and the second anti-reflection layer are formed of silicon nitride (SiN x ) having positive fixed charges.   
     
     
         17 . The solar cell of  claim 16 , wherein the first anti-reflection layer and the second anti-reflection layer each have a refractive index of about 1.9 to 2.3 and a thickness of about 50 nm to 100 nm. 
     
     
         18 . The solar cell of  claim 5 , wherein a surface of the substrate, at which the emitter region is positioned, is formed as a first textured surface,
 wherein a surface of the substrate, at which the back surface field region is positioned, is formed as a second textured surface.   
     
     
         19 . The solar cell of  claim 5 , wherein the substrate is formed of an n-type silicon wafer doped with phosphorus (P). 
     
     
         20 . The solar cell of  claim 5 , wherein the emitter region includes a first doped region which is lightly doped with impurities of the second conductive type, and a second doped region which is more heavily doped than the first doped region with impurities of the second conductive type.