Nanostructured solar cells

Abstract

Improved photovoltaic devices and methods are disclosed. In one embodiment, an exemplary photovoltaic device includes a semiconductor layer and a light-responsive layer (which can be made, for example, of a semiconductor material) which form a junction, such as a p-n junction. The light-responsive layer can include a plurality of carbon nanostructures, such as carbon nanotubes, located therein. In many cases, the carbon nanostructures can provide a conductive pathway within the light-responsive layer. In other embodiments, exemplary photovoltaic devices include semiconductor nanostructures, which can take a variety of forms, in addition to the carbon nanostructures. Further embodiments include a wide variety of other configurations and features. Methods of fabricating photovoltaic devices are also disclosed.

1 . A photovoltaic device comprising:
 a first semiconductor layer; and   a second layer forming a junction with said first layer, said junction including a depletion region, wherein the second layer comprises:
 a semiconductor material; and 
 a plurality of carbon nanostructures substantially vertically oriented relative to an electrically conductive layer, wherein the plurality of carbon nanostructures contact the electrically conductive layer, and the carbon nanostructures exhibit a vanishing band gap. 
   
     
     
         2 . The photovoltaic device of  claim 1 , wherein the plurality of carbon nanostructures are spaced apart at regular intervals. 
     
     
         3 . The photovoltaic device of  claim 1 , wherein the plurality of carbon nanostructures are grouped into bunches. 
     
     
         4 . The photovoltaic device of  claim 1 , wherein the plurality of carbon nanostructures are multi-wall carbon nanotubes. 
     
     
         5 . The photovoltaic device of  claim 1 , wherein the plurality of carbon nanostructures are single-wall carbon nanotubes. 
     
     
         6 . The photovoltaic device of  claim 1 , further comprising a plurality of semiconductor nanostructures disposed on portions of an outer surface of at least one of said plurality of carbon nanostructures. 
     
     
         7 . The photovoltaic device of  claim 6 , wherein the portions of the outer surface of the plurality of carbon nanostructures between the plurality of semiconductor nanostructures are coated with an insulating material. 
     
     
         8 . The photovoltaic device of  claim 1 , wherein the semiconductor nanostructures provide a carbon nanostructure core. 
     
     
         9 . The photovoltaic device of  claim 1 , further comprising an insulating layer separating the semiconductor material and the electrical contact, wherein the plurality of carbon nanostructures extend through the insulating layer. 
     
     
         10 . The photovoltaic device of  claim 1 , wherein the semiconductor material conformally coats at least one of the plurality of carbon nanostructures. 
     
     
         11 . The photovoltaic device of  claim 1 , wherein the junction is substantially planar. 
     
     
         12 . The photovoltaic device of  claim 1 , wherein the junction is non-planar. 
     
     
         13 . The photovoltaic device of  claim 1 , wherein the plurality of carbon nanostructures have interstices therebetween, wherein the interstices are sized such that electron-hole pairs generated in the interstices are located a distance apart from any carbon nanostructure that is less than about three diffusion lengths of photo-generated minority carriers in the semiconductor material included in the second layer. 
     
     
         14 . The photovoltaic device of  claim 1 , wherein the semiconductor material exhibits a crystalline structure. 
     
     
         15 . A photovoltaic device comprising:
 a first semiconductor layer;   a second layer disposed adjacent said first layer so as to form a junction therewith, said junction having a depletion region;   a plurality of carbon nanostructures distributed in said second layer, wherein the carbon nanostructures are substantially vertically oriented relative to an electrically conductive layer; and   a plurality of semiconductor nanostructures disposed on at least some of said carbon nanostructures.   
     
     
         16 . The photovoltaic device of  claim 15 , wherein the plurality of carbon nanostructures are spaced apart at regular intervals. 
     
     
         17 . The photovoltaic device of  claim 15 , wherein the plurality of carbon nanostructures are grouped into bunches. 
     
     
         18 . The photovoltaic device of  claim 15 , wherein the portions of the outer surface of the plurality of carbon nanostructures between the plurality of semiconductor nanostructures are coated with an insulating material. 
     
     
         19 . The photovoltaic device of  claim 15 , wherein the semiconductor nanostructures provide a carbon nanostructure core. 
     
     
         20 . The photovoltaic device of  claim 15 , further comprising an insulating layer separating the semiconductor material and the electrical contact, wherein the plurality of carbon nanostructures extend through the insulating layer. 
     
     
         21 . The photovoltaic device of  claim 15 , wherein the plurality of carbon nanostructures have interstices therebetween, wherein the interstices are sized such that electron-hole pairs generated in the interstices are located a distance apart from any carbon nanostructure that is less than about three diffusion lengths of photo-generated minority carriers in the semiconductor material included in the second layer. 
     
     
         22 . The photovoltaic device of  claim 15 , wherein the semiconductor material exhibits a crystalline structure.