Methods for Manufacturing a Contact Grid on a Photovoltaic Cell

Abstract

Processes for fabricating a contact grid for a photovoltaic cell generally includes providing a photovoltaic cell having an antireflective coating disposed on a sun facing side, the photovoltaic cell comprising a silicon substrate having a p-n junction; soft stamping a pattern of a UV sensitive photoresist and/or polymer onto the antireflective coating; exposing the UV sensitive photoresist and/or polymer to ultraviolet radiation to cure the UV sensitive photoresist and/or polymer; etching the pattern to form openings in the antireflective coating that define the contact grid; stripping the UV sensitive photoresist and/or polymer; and depositing a conductive metal into the openings defined by the pattern. The metal based paste can be aluminum based, which can be annealed at a relatively low temperature.

1 . A process for fabricating a contact grid for a photovoltaic cell, the process comprising:
 providing a photovoltaic cell having an antireflective coating disposed on a sun facing side, the photovoltaic cell comprising a silicon substrate having a p-n junction;   soft stamping a pattern of a UV sensitive photoresist and/or polymer onto the antireflective coating;   exposing the UV sensitive photoresist and/or polymer to ultraviolet radiation to cure the UV sensitive photoresist and/or polymer;   etching the pattern to form openings in the antireflective coating that define the contact grid;   stripping the UV sensitive photoresist and/or polymer; and   depositing a conductive metal into the openings defined by the pattern.   
     
     
         2 . The process of  claim 1 , wherein the contact grid includes bus bars. 
     
     
         3 . The process of  claim 1 , wherein etching the pattern comprises a phosphoric acid based wet etching chemistry. 
     
     
         4 . The process of  claim 1 , wherein stripping the UV sensitive photoresist and/or polymer comprises exposing the UV sensitive photoresist and/or polymer to hydrofluoric acid. 
     
     
         5 . The process of  claim 1 , wherein depositing the conductive metal comprises stamping metal paste into the pattern; and annealing the metal paste. 
     
     
         6 . The process of  claim 5 , wherein annealing the metal paste is at a temperature of less than 400° C. 
     
     
         7 . The process of  claim 5 , wherein the metal paste is aluminum based. 
     
     
         8 . The process of  claim 5 , wherein stamping the metal paste into the openings of the pattern comprises dipping a stamp into the metal paste, wherein the stamp comprises a plurality of projections corresponding to the openings having a diameter and/or width smaller than the openings defined by the pattern; inserting the projections into the openings; and filling the openings with the metal paste. 
     
     
         9 . The process of  claim 8 , wherein stamping the metal paste into the openings of the pattern is subsequent to exposing the UV sensitive photoresist and/or polymer to ultraviolet radiation to cure the UV sensitive photoresist and/or polymer and etching the pattern in the antireflective coating to form the openings and prior to stripping the UV sensitive photoresist and/or polymer. 
     
     
         10 . A process for fabricating a contact grid for a photovoltaic cell, the process comprising:
 providing a photovoltaic cell having an antireflective coating disposed on a sun facing side, the photovoltaic cell comprising a silicon substrate having a p-n junction;   stamping a pattern of a photoresist and/or polymer onto the antireflective coating;   curing the photoresist and/or polymer;   etching the pattern in the antireflective coating to form openings that define the contact grid;   stripping the UV sensitive photoresist and/or polymer;   stamping an aluminum based metal paste into the openings of the pattern by dipping a stamp into the aluminum based metal paste, wherein the stamp comprises a plurality of projections corresponding to the openings having a diameter and/or width smaller than the openings; stamping the projections into the openings; and filling the openings with the metal paste; and   annealing the aluminum based metal paste.   
     
     
         11 . The process of  claim 10 , wherein the contact grid includes bus bars. 
     
     
         12 . The process of  claim 10 , wherein etching the pattern comprises a phosphoric acid based wet etching chemistry. 
     
     
         13 . The process of  claim 10 , wherein stripping the UV sensitive photoresist and/or polymer from the antireflective coating comprises exposing the UV sensitive photoresist and/or polymer to hydrofluoric acid. 
     
     
         14 . The process of  claim 10 , wherein annealing the aluminum based metal paste comprises heating to at a temperature of less than 400° C. 
     
     
         15 . The process of  claim 10 , wherein stamping the aluminum based metal paste into the openings of the pattern is subsequent to curing the UV sensitive photoresist and/or polymer and etching the pattern in the antireflective coating to form the openings and prior to stripping the UV sensitive photoresist and/or polymer.