Preparation of CIGS-based solar cells using a buffered electrodeposition bath

Abstract

A photovoltaic cell exhibiting an overall conversion efficiency of at least 9.0% is prepared from a copper-indium-gallium-diselenide thin film. The thin film is prepared by simultaneously electroplating copper, indium, gallium, and selenium onto a substrate using a buffered electro-deposition bath. The electrodeposition is followed by adding indium to adjust the final stoichiometry of the thin film.

What is claimed is:  
     
         1 . A thin film photovoltaic cell formed from at least one semiconductor layer, wherein said at least one semiconductor layer includes a copper-indium-gallium-diselenide film having a band gap ranging from 1.1-1.45 eV, and said thin film photovoltaic cell has a conversion efficiency of at least 9.0%, an open circuit voltage of at least 0.4 V, a current of at least 30 mA/cm 2 , and a fill factor of at least 58%.  
     
     
         2 . A method for preparing a copper-indium-gallium-diselenide film comprising: 
 providing a substrate;    providing a buffered electro-deposition bath containing ions of copper, indium, gallium, and selenide; and    placing said substrate in said buffered electro-deposition bath to form a semiconductor layer having copper, indium, gallium, and selenide.    
     
     
         3 . The method according to  claim 2  wherein said substrate is selected from the group consisting of glass, amorphous glass, and soda-lime silica glass.  
     
     
         4 . The method according to  claim 3  further including applying a molybdenum layer to said substrate.  
     
     
         5 . The method according to  claim 4  further including adjusting said semiconductor layer composition by physical vapor deposition.  
     
     
         6 . The method according to  claim 5  wherein adjusting said semiconductor layer composition further includes adding indium by physical vapor deposition.  
     
     
         7 . A method for preparing a copper-indium-gallium-diselenide film comprising: 
 providing a substrate;    providing a buffered electro-deposition bath containing ions of copper, indium, gallium, and selenide;    placing said substrate in said buffered electro-deposition bath to form a semiconductor layer having copper, indium, gallium, and selenide; and    adjusting said semiconductor layer composition by depositing indium by physical vapor deposition.    
     
     
         8 . The method according to  claim 7  wherein said substrate is selected from the group consisting of glass, amorphous glass, and soda-lime silica glass.  
     
     
         9 . The method according to  claim 8  further including applying a molybdenum layer to said substrate.  
     
     
         10 . A method of fabricating a thin film photovoltaic device, comprising: 
 (a) providing a substrate;    (b) applying a molybdenum layer to said substrate by radio frequency sputtering;    (c) providing a buffered electro-deposition bath containing ions of copper, indium, gallium, and selenide;    (d) placing said substrate in said buffered electro-deposition bath to form a semiconductor layer having copper, indium, gallium, and selenide;    (e) adjusting said semiconductor layer composition by depositing indium by physical vapor deposition;    (f) depositing a negative-type semiconductor layer by electro-deposition to said semiconductor layer, wherein said negative-type semiconductor layer is comprised of cadmium sulfide;    (g) depositing a first zinc oxide layer by radio frequency sputtering to said negative-type semiconductor layer    (h) depositing an aluminum oxide doped zinc oxide layer by radio frequency sputtering to said first zinc oxide layer;    (i) applying a Nickel/Aluminum electrical contact layer to said aluminum oxide doped zinc oxide layer; and    (j) depositing a anti-reflective coating composed of magnesium fluoride onto said electrical contact layer.    
     
     
         11 . The method according to  claim 10  wherein said substrate is selected from the group consisting of glass, amorphous glass, and soda-lime silica glass.