Contact for silicon heterojunction solar cells

Abstract

A photovoltaic device and method include a substrate coupled to an emitter side structure on a first side of the substrate and a back side structure on a side opposite the first side of the substrate. The emitter side structure or the back side structure include layers alternating between wide band gap layers and narrow band gap layers to provide a multilayer contact with an effectively increased band offset with the substrate and/or an effectively higher doping level over a single material contact. An emitter contact is coupled to the emitter side structure on a light collecting end portion of the device. A back contact is coupled to the back side structure opposite the light collecting end portion.

1 .- 16 . (canceled) 
     
     
         17 . A method for fabricating a photovoltaic device, comprising:
 providing a substrate;   forming a plurality of layers including alternating wide band gap and narrow band gap layers to form a superlattice to provide a multilayer with an effectively increased band offset with the substrate and/or effectively increased doping level over a single material contact;   forming a conductive contact on the superlattice; and   forming a contact structure on the substrate on a side opposite the superlattice.   
     
     
         18 . The method as recited in  claim 17 , wherein forming a plurality of layers includes forming a plurality of doped layers and intrinsic layers. 
     
     
         19 . The method as recited in  claim 17 , wherein forming a plurality of layers includes forming a plurality of wide band gap doped layers, and narrow band gap intrinsic layers. 
     
     
         20 . The method as recited in  claim 17 , wherein forming a contact structure includes forming another superlattice and conductive contact. 
     
     
         21 . The method as recited in  claim 17 , further comprising forming an intrinsic layer between the substrate and the superlattice. 
     
     
         22 . The method as recited in  claim 17 , further comprising forming a doped contact layer between the superlattice and conductive contact. 
     
     
         23 . The method as recited in  claim 17 , wherein forming a plurality of layers includes forming the layers with a thickness of less than about 20 nm. 
     
     
         24 . The method as recited in  claim 17 , wherein the substrate includes crystalline silicon and the wide band gap layers include one of amorphous silicon, amorphous silicon carbide and amorphous silicon nitride. 
     
     
         25 . The method as recited in  claim 17 , wherein the substrate includes crystalline silicon and the narrow band gap layers include one of amorphous silicon, amorphous germanium, amorphous silicon germanium and nano- or micro crystalline silicon.