Manufacturing Apparatus and Method for Large-Scale Production of Thin-Film Solar Cells

Abstract

A method of manufacturing improved thin-film solar cells entirely by sputtering includes a high efficiency back contact/reflecting multi-layer containing at least one barrier layer consisting of a transition metal nitride. A copper indium gallium diselenide (Cu(In X Ga 1-X )Se 2 ) absorber layer (X ranging from 1 to approximately 0.7) is co-sputtered from specially prepared electrically conductive targets using dual cylindrical rotary magnetron technology. The band gap of the absorber layer can be graded by varying the gallium content, and by replacing the gallium partially or totally with aluminum. Alternately the absorber layer is reactively sputtered from metal alloy targets in the presence of hydrogen selenide gas. RF sputtering is used to deposit a non-cadmium containing window layer of ZnS. The top transparent electrode is reactively sputtered aluminum doped ZnO. A unique modular vacuum roll-to-roll sputtering machine is described. The machine is adapted to incorporate dual cylindrical rotary magnetron technology to manufacture the improved solar cell material in a single pass.

What is claimed is: 
     
         1 . A method of making a conductive sputtering target comprising a mixture of copper, indium and at least one of aluminum and gallium, the method comprising forming the target by powder metallurgy or casting such that an atomic ratio of copper to indium and at least one of aluminum and gallium in the target is less than one. 
     
     
         2 . The method of  claim 1 , wherein the target consists essentially of the mixture of copper, indium and aluminum, such that the atomic ratio of copper to indium and aluminum is less than one. 
     
     
         3 . The method of  claim 1 , wherein the target consists essentially of the mixture of copper, indium and gallium, such that the atomic ratio of copper to indium and gallium is less than one. 
     
     
         4 . The method of  claim 1 , further comprising disposing the target on a planar or cylindrical rotary magnetron. 
     
     
         5 . The method of  claim 1 , wherein the target is formed by powder metallurgy. 
     
     
         6 . The method of  claim 1 , wherein the target is formed by casting. 
     
     
         7 . A conductive sputtering target comprising a mixture of copper, indium and at least one of aluminum and gallium, such that an atomic ratio of copper to indium and at least one of aluminum and gallium is less than one. 
     
     
         8 . The target of  claim 7 , wherein the target consists essentially of the mixture of copper, indium and aluminum, such that the atomic ratio of copper to indium and aluminum is less than one. 
     
     
         9 . The target of  claim 7 , wherein the target consists essentially of the mixture of copper, indium and gallium, such that the atomic ratio of copper to indium and gallium is less than one. 
     
     
         10 . The target of  claim 7 , wherein the target is disposed on a planar or cylindrical rotary magnetron. 
     
     
         11 . The target of  claim 7 , wherein the target further comprises sodium.