Leakage pathway layer for solar cell

Abstract

Leakage pathway layers for solar cells and methods of forming leakage pathway layers for solar cells are described.

What is claimed is: 
     
         1 . A method of fabricating a solar cell, the method comprising:
 forming a dielectric layer above a substrate, the dielectric layer having a first thickness;   thinning the dielectric layer to a second thickness, less than the first thickness;   forming a leakage pathway layer above the dielectric layer having the second thickness; and   forming an anti-reflective coating layer above the leakage pathway layer.   
     
     
         2 . The method of  claim 1 , wherein forming the leakage pathway layer comprises forming a layer of phosphorus- or boron-doped silicon with a morphology selected from the group consisting of amorphous, nano-crystalline, and fine-grained. 
     
     
         3 . The method of  claim 2 , wherein forming the layer of phosphorus- or boron-doped silicon comprises depositing the layer to have a thickness less than 10 nanometers in a plasma-enhanced chemical vapor deposition chamber. 
     
     
         4 . The method of  claim 3 , wherein depositing the layer to have a thickness less than 10 nanometers comprises depositing to a thickness of approximately 5 nanometers. 
     
     
         5 . The method of  claim 1 , wherein the solar cell is a back-contact solar cell, and wherein forming the dielectric layer above the substrate comprises forming the dielectric layer on a light-receiving surface of the substrate. 
     
     
         6 . The method of  claim 1 , wherein forming the dielectric layer above the substrate comprises forming the dielectric layer directly on the substrate, wherein forming the leakage pathway layer above the dielectric layer comprises forming the leakage pathway layer directly on the dielectric layer, and wherein forming the anti-reflective coating layer above the leakage pathway layer comprises forming the anti-reflective coating layer directly on the leakage pathway layer. 
     
     
         7 . The method of  claim 1 , wherein the dielectric layer comprises silicon dioxide, and thinning the dielectric layer to the second thickness comprises etching the dielectric layer with an etchant selected from the group consisting of an aqueous solution of hydrofluoric acid or a CF 4 , NF 3 , CxFy or SF 6 -based plasma. 
     
     
         8 . The method of  claim 7 , wherein thinning the dielectric layer to the second thickness, less than the first thickness, comprises thinning the dielectric layer from the first thickness approximately in the range of 65-75 Angstroms to the second thickness approximately in the range of 35-45 Angstroms. 
     
     
         9 . The method of  claim 7 , wherein a CF 4 , NF 3 , CxFy or SF 6 -based plasma is used, and thinning the dielectric layer to the second thickness comprises etching the dielectric layer in the same process chamber in which the dielectric layer is formed, without removing the substrate between the forming and the thinning of the dielectric layer. 
     
     
         10 . The method of  claim 1 , wherein thinning the dielectric layer to the second thickness comprises reducing or eliminating a number of surface defects in the dielectric layer. 
     
     
         11 . The method of  claim 1 , wherein forming the anti-reflective coating layer above the leakage pathway layer comprises forming a layer of silicon nitride with a thickness approximately in the range of 70-80 nanometers. 
     
     
         12 . The method of  claim 1 , wherein thinning the dielectric layer to the second thickness enables an electric field effect on a solar-receiving surface of the solar cell, the electric field effect comprising a band-bending into the substrate. 
     
     
         13 . A method of fabricating a solar cell, the method comprising:
 forming a dielectric layer above a substrate, the dielectric layer having a first thickness;   thinning the dielectric layer to a second thickness, less than the first thickness; and   forming an anti-reflective coating layer above the dielectric layer having the second thickness.   
     
     
         14 . The method of  claim 13 , wherein thinning the dielectric layer to the second thickness, less than the first thickness, comprises thinning the dielectric layer to a thickness suitable to force direct tunneling from the anti-reflective coating layer, through the dielectric layer, to the substrate. 
     
     
         15 . The method of  claim 13 , wherein forming the dielectric layer above the substrate comprises forming a doped dielectric layer above the substrate, wherein the method further comprises driving dopants from the doped dielectric layer into the substrate to provide a depleted dielectric layer, and wherein thinning the dielectric layer to the second thickness comprises thinning the depleted dielectric layer. 
     
     
         16 . The method of  claim 15 , wherein thinning the dielectric layer to the second thickness enables an electric field effect on a solar-receiving surface of the solar cell, the electric field effect comprising a band-bending into the substrate.