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.

1 - 20 . (canceled) 
     
     
         21 . A solar cell comprising:
 a silicon substrate having a textured front surface and a back surface opposite the front surface, the front surface facing the sun to collect solar radiation during normal operation;   an antireflective layer over the textured front surface of the silicon substrate;   a doped diffusion region in the silicon substrate, the doped diffusion region proximate to the textured front surface of the silicon substrate;   a tunnel oxide layer formed on the back surface of the silicon substrate, the tunnel oxide layer having a thickness of about 10 to 50 Angstroms;   a doped polysilicon emitter layer formed on the tunnel oxide layer, the doped polysilicon emitter layer and the doped diffusion region having opposite conductivity types;   a front metal contact disposed on and in contact with the front surface of the silicon substrate; and   a rear metal contact disposed on and in contact with the doped polysilicon emitter layer.   
     
     
         22 . The solar cell of  claim 21 , wherein the antireflective layer comprises silicon nitride. 
     
     
         23 . The solar cell of  claim 21  comprising an oxide layer formed on the textured front surface of the silicon substrate. 
     
     
         24 . The solar cell of  claim 23 , wherein the oxide layer comprises silicon dioxide. 
     
     
         25 . The solar cell of  claim 24 , wherein the silicon dioxide is thermally grown to a thickness of about 10 to 250 Angstroms. 
     
     
         26 . The solar cell of  claim 21 , wherein the tunnel oxide layer comprises silicon dioxide. 
     
     
         27 . The solar cell of  claim 26 , wherein the tunnel oxide layer is thermally grown. 
     
     
         28 . The solar cell of  claim 21  comprising a dielectric layer formed on the doped polysilicon emitter layer. 
     
     
         29 . The solar cell of  claim 28  wherein the dielectric layer comprises contact holes through which rear metal contact makes an electrical connection with the doped polysilicon emitter layer. 
     
     
         30 . The solar cell of  claim 21 , wherein rear metal contact comprises silver. 
     
     
         31 . The solar cell of  claim 21  comprising a front bus bar attached to a front side of the solar cell, the front bus bar in electrical contact with the front metal contact. 
     
     
         32 . The solar cell of  claim 21  comprising a rear bus bar attached to a rear side of the solar cell, the rear bus bar in electrical contact with the rear metal contact. 
     
     
         33 . The solar cell of  claim 21 , wherein the silicon substrate has a thickness measured from the back surface to a tip of the textured front surface of about 100 to 250 μm. 
     
     
         34 . The solar cell of  claim 21 , wherein the silicon substrate is a N-type silicon substrate.