Front contact solar cell with formed emitter

Abstract

A bipolar solar cell includes a backside junction formed by an N-type silicon substrate and a P-type polysilicon emitter formed on the backside of the solar cell. An antireflection layer may be formed on a textured front surface of the silicon substrate. A negative polarity metal contact on the front side of the solar cell makes an electrical connection to the substrate, while a positive polarity metal contact on the backside of the solar cell makes an electrical connection to the polysilicon emitter. An external electrical circuit may be connected to the negative and positive metal contacts to be powered by the solar cell. The positive polarity metal contact may form an infrared reflecting layer with an underlying dielectric layer for increased solar radiation collection.

What is claimed is: 
     
         1 . A solar cell, comprising:
 a substrate;   a first tunnel dielectric disposed over the substrate;   an emitter disposed over the first tunnel dielectric;   a front electrode disposed over a front surface of the substrate; and   a back electrode disposed over a back surface of the substrate.   
     
     
         2 . The solar cell of  claim 1 , wherein the emitter is a polysilicon emitter. 
     
     
         3 . The solar cell of  claim 1 , wherein the substrate is a monocrystalline silicon substrate. 
     
     
         4 . The solar cell of  claim 1 , wherein the first tunnel dielectric is a tunnel oxide. 
     
     
         5 . The solar cell of  claim 1 , wherein the emitter is disposed over the back surface of the substrate. 
     
     
         6 . The solar cell of  claim 1 , further comprising a second tunnel dielectric disposed on an opposite side of the substrate than the first tunnel dielectric. 
     
     
         7 . The solar cell of  claim 1 , wherein the back electrode includes silver. 
     
     
         8 . The solar cell of  claim 1 , further comprising an antireflective layer disposed over the front surface of the substrate. 
     
     
         9 . A solar cell, comprising:
 a substrate;   an emitter over a back surface of the substrate;   a first dielectric between the emitter and back surface;   a front electrode disposed on a front surface of the solar cell; and   a back electrode disposed on a back surface of the solar cell.   
     
     
         10 . The solar cell of  claim 9 , wherein the emitter is a polysilicon emitter. 
     
     
         11 . The solar cell of  claim 9 , wherein the substrate is a monocrystalline silicon substrate. 
     
     
         12 . The solar cell of  claim 9 , wherein the first dielectric is an oxide. 
     
     
         13 . The solar cell of  claim 9 , further comprising a second dielectric disposed on an opposite side of the substrate than the first dielectric. 
     
     
         14 . The solar cell of  claim 9 , wherein the back electrode includes silver. 
     
     
         15 . A method of fabricating a solar cell, the method comprising:
 forming a first tunnel dielectric on a front surface of a substrate;   forming a second tunnel dielectric on a back surface of the substrate;   forming an emitter over the first or second tunnel dielectric;   forming a front side electrode on a front surface of the solar cell; and   forming a back side electrode on a back surface of the solar cell.   
     
     
         16 . The method of  claim 15 , wherein said forming the emitter comprises forming a polysilicon emitter. 
     
     
         17 . The method of  claim 15 , wherein said forming the emitter comprises forming a first silicon layer on the second tunnel dielectric. 
     
     
         18 . The method of  claim 17 , further comprising forming a second silicon layer on the first tunnel dielectric. 
     
     
         19 . The method of  claim 18 , wherein forming the first and second silicon layers comprises forming first and second polysilicon layers, respectively. 
     
     
         20 . The method of  claim 15 , wherein said forming the second tunnel dielectric comprises forming an oxide.