Integrated solar collectors using epitaxial lift off and cold weld bonded semiconductor solar cells

Abstract

There is disclosed ultrahigh-efficiency single- and multi-junction thin-film solar cells. This disclosure is also directed to a substrate-damage-free epitaxial lift-off (“ELO”) process that employs adhesive-free, reliable and lightweight cold-weld bonding to a substrate, such as bonding to plastic or metal foils shaped into compound parabolic metal foil concentrators. By combining low-cost solar cell production and ultrahigh-efficiency of solar intensity-concentrated thin-film solar cells on foil substrates shaped into an integrated collector, as described herein, both lower cost of the module as well as significant cost reductions in the infrastructure is achieved.

1 . A thin-film solar cell comprising:
 a first substrate;   a metal contact bonded to said first substrate;   an active photovoltaic region bonded to said metal contact;   one or more first protection layers, wherein at least one of said first protection layers comprise at least one compound chosen from InGaP, GaAs, InGaAs, InP, and InAlP;   an AlAs layer;   one or more second protection layers, wherein at least one of said second protection layers comprise at least one compound chosen from InGaP, GaAs, InGaAs, InP, and InAlP;   and a second substrate, wherein said second substrate comprises at least one compound chosen from GaAs and InP.   
     
     
         2 . The thin-film solar cell according to  claim 1 , wherein said thin-film solar cell comprises two first and/or second protection layers. 
     
     
         3 . The thin-film solar cell according to  claim 1 , wherein said thin-film solar cell comprises three first and/or second protection layers. 
     
     
         4 . The thin-film solar cell according to  claim 1 , wherein said first substrate comprises a plastic or a metal foil. 
     
     
         5 . The thin-film solar cell according to  claim 4 , wherein said first substrate comprises a polyimide film. 
     
     
         6 . The thin-film solar cell according to  claim 1 , wherein said metal contact comprises at least one metal chosen from Au, Ag, and Cu. 
     
     
         7 . The thin-film solar cell according to  claim 6 , wherein said metal contact comprises Au. 
     
     
         8 . The thin-film solar cell according to  claim 6 , wherein said metal contact comprises Cu. 
     
     
         9 . The thin-film solar cell according to  claim 1 , wherein said thin-film solar cell is integrated into a solar collector, wherein said solar collector is molded into a shape chosen from a compound parabolic collector or a Winston collector. 
     
     
         10 . A method for performing an epitaxial lift-off process, comprising:
 growing one or more first protection layers on a first substrate, wherein at least one of said protection layers comprise a compound chosen from InGaP, GaAs, InGaAs, InP, and InAlP;   growing an AlAs layer;   growing one or more second protection layers, wherein at least one of said protection layers comprise a compound chosen from InGaP, GaAs, InGaAs, InP, and InAlP;   depositing at least one active photovoltaic cell layers on top of the second protection layer;   coating the top active photovoltaic cell layer with a metal;   coating a second substrate with a metal;   pressing together the two metal surfaces to form a cold-weld bond;   and removing the AlAs layer with a selective chemical etchant.   
     
     
         11 . The method of  claim 10 , wherein each additional protection layer is removed with a selective chemical etchant. 
     
     
         12 . The method of  claim 11 , wherein the first substrate is solvent cleaned and treated to form an oxide layer. 
     
     
         13 . The method of  claim 10 , wherein the second substrate is chosen from a plastic or a metal foil. 
     
     
         14 . The method of  claim 13 , wherein the second substrate is chosen from a polyimide film. 
     
     
         15 . The method of  claim 10 , wherein said metal contact comprises at least one metal chosen from Au, Ag, and Cu. 
     
     
         16 . The method of  claim 15 , wherein said metal contact comprises Au. 
     
     
         17 . The method of  claim 15 , wherein said metal contact comprises Cu.