Solar cell

Abstract

Discussed is a solar cell including a silicon substrate, an emitter area formed on a front surface of the silicon substrate, a tunneling oxide layer formed on a back surface of the silicon substrate, a back surface field area formed on the tunneling oxide layer and formed of a polycrystalline silicon layer, a front passivation film on the emitter area, a front electrode connected to the emitter area by penetrating through the front passivation film, a back passivation film formed on the back surface field area and having an opening and a back electrode connected to the back surface field area via the opening.

1 . A solar cell comprising:
 a silicon substrate;   an emitter area formed on a front surface of the silicon substrate;   a tunneling oxide layer formed on a back surface of the silicon substrate;   a back surface field area formed on the tunneling oxide layer and formed of a polycrystalline silicon layer;   a front passivation film on the emitter area;   a front electrode connected to the emitter area by penetrating through the front passivation film;   a back passivation film formed on the back surface field area and having an opening; and   a back electrode connected to the back surface field area via the opening.   
     
     
         2 . The solar cell according to  claim 1 , wherein the emitter area is formed by diffusing a first conductive type dopant into the silicon substrate. 
     
     
         3 . The solar cell according to  claim 2 , wherein the silicon substrate has a second conductive type dopant having a conductive type opposite to a conductive type of the first conductive type dopant. 
     
     
         4 . The solar cell according to  claim 1 , wherein the back surface field area has a dopant having a conductive type the same as a conductive type of the silicon substrate. 
     
     
         5 . The solar cell according to  claim 1 , wherein the back electrode is directly contacted with the back surface field area. 
     
     
         6 . The solar cell according to  claim 1 , wherein the back surface field area has a p-type conductivity, and
 wherein the back passivation film includes at least one of aluminum oxide, zirconium oxide, and hafnium oxide having a negative charge.   
     
     
         7 . The solar cell according to  claim 1 , wherein the back surface field area has an n-type conductivity, and
 wherein the back passivation film includes at least one of silicon oxide and silicon nitride having a positive charge.   
     
     
         8 . The solar cell according to  claim 1 , further comprising:
 an additional film on the back passivation film.   
     
     
         9 . The solar cell according to  claim 8 , wherein the additional film includes at least one selected from the group consisting of silicon nitride, silicon nitride containing hydrogen, silicon oxide, silicon oxide nitride, aluminum oxide, MgF 2 , ZnS, TiO 2  and CeO 2 . 
     
     
         10 . The solar cell according to  claim 1 , wherein the tunneling oxide layer has a thickness of about 0.5 nm to 5 nm. 
     
     
         11 . The solar cell according to  claim 1 , further comprising:
 an additional back surface field area at a portion of the silicon substrate facing the tunneling oxide layer.   
     
     
         12 . The solar cell according to  claim 11 , wherein the additional back surface field area has a dopant having a conductive type the same as a conductive type of a dopant of the back surface field area. 
     
     
         13 . The solar cell according to  claim 11 , wherein the additional back surface field area has the same crystalline structure as the silicon substrate. 
     
     
         14 . The solar cell according to  claim 1 , wherein the silicon substrate is formed of a monocrystalline silicon substrate. 
     
     
         15 . The solar cell according to  claim 1 , further comprising:
 an additional film on the back passivation film,   wherein the back electrode comprises a plurality of finger electrodes disposed in parallel to each other with a regular pitch, and   wherein a portion of the additional film exposed between the plurality of finger electrodes acts as an anti-reflection film for preventing reflection of light incident through the back surface of the silicon substrate.   
     
     
         16 . The solar cell according to  claim 1 , wherein the emitter area includes a first region that is directly contacted with the front electrode and a second region having a dopant concentration lower than a dopant concentration of the first region. 
     
     
         17 . The solar cell according to  claim 1 , wherein a crystalline structure of the emitter area is the same with a crystalline structure of the silicon substrate and different from a crystalline structure of the back surface field area. 
     
     
         18 . The solar cell according to  claim 1 , wherein the back electrode is not directly formed on the back passivation film. 
     
     
         19 . The solar cell according to  claim 1 , wherein a thickness of the back surface field area is about 50 nm to 500 nm. 
     
     
         20 . The solar cell according to  claim 1 , wherein a thickness of the back surface field area being about 50 nm to 500 nm is provided when a crystalline structure of the polycrystalline silicon back surface field area is different from that of the monocrystalline silicon substrate and that of the emitter area.