Graphene-based multi-junctions flexible solar cell

Abstract

This disclosure relates to structures for the conversion of light into energy. More specifically, the disclosure describes devices for conversion of light to electricity using photovoltaic cells comprising graphene.

What is claimed is: 
     
         1 . A method of making a graphene solar cell comprising:
 forming a first monoatomic graphene layer on a substrate, the first monoatomic graphene layer comprising a first dopant distributed with the entire first monoatomic graphene layer; and   forming a second monoatomic graphene layer on the first monoatomic graphene layer such that the second monoatomic graphene layer is in contact with the first monoatomic graphene layer in a stacked configuration, the second monoatomic graphene layer comprising a second dopant distributed with the entire second monoatomic graphene layer,   wherein the first dopant is either an n-type dopant or a p-type dopant such that:
 the second dopant is a p-type dopant if the first dopant is the n-type dopant; and 
 the second dopant is an n-type dopant if the first dopant is the p-type dopant. 
   
     
     
         2 . The method of  claim 1 , wherein the first and second monoatomic graphene layers form a first sub-cell of the solar cell, the method further comprising forming a second sub-cell above the first sub-cell. 
     
     
         3 . The method of  claim 2 , wherein the first and second sub-cells each have a different band gap energy. 
     
     
         4 . The method of  claim 3 , wherein a difference in band gap energy between the first and second sub-cells is about 0.25 eV or more. 
     
     
         5 . The method of  claim 2 , further comprising placing a transparent conductive substrate separating between each sub-cell. 
     
     
         6 . The method of  claim 5 , further comprising forming an anti-reflective coating and a first metal contact in a position where incident solar energy will pass by the anti-reflective coating and the first metal contact prior to reaching the sub-cells. 
     
     
         7 . The method of  claim 6 , further comprising forming a second metal contact on the substrate prior to forming the sub-cells. 
     
     
         8 . The method of  claim 1 , wherein the n-type dopant is nitrogen or phosphorous. 
     
     
         9 . The method of  claim 1 , wherein the p-type dopant is boron or aluminum. 
     
     
         10 . The method of  claim 1 , wherein forming the first monoatomic graphene layer on the substrate comprises depositing the first monoatomic graphene layer on the substrate with chemical vapor deposition. 
     
     
         11 . The method of  claim 1 , further comprising forming a first plurality of monoatomic graphene layers on the substrate prior to forming the first monoatomic graphene layer, each of the first plurality of monoatomic graphene layers comprising a dopant that is the same type as the first dopant. 
     
     
         12 . The method of  claim 11 , further comprising forming a second plurality of monoatomic graphene layers on the substrate after forming the second monoatomic graphene layer, each of the second plurality of monoatomic graphene layers comprising a dopant that is the same type as the second dopant. 
     
     
         13 . A method of making a graphene multijunction solar cell comprising:
 forming a monoatomic graphene layer of either p-doped or n-doped graphene on a thin film of metal;   placing a transparent conductive flexible substrate having a thin film of transparent conductive oxide onto a surface of the monoatomic graphene layer;   removing the metal film from the monoatomic graphene layer;   oxidizing the monoatomic graphene layer to open up its band gap to provide an n-type graphene-flexible substrate assembly;   reducing the monoatomic graphene layer to open up its band gap to provide a p-type graphene-flexible substrate assembly;   combining one or more other graphene-flexible substrate assemblies that have equal band gap but opposite doping to provide a p-n-doped graphene assembly; and   stacking one or more p-n-doped assembly or sub-cell on top or on bottom of other of p-n-doped assembly or sub-cell with the same or different band gaps.   
     
     
         14 . The method of  claim 13 , wherein the depositing is by chemical vapor deposition techniques. 
     
     
         15 . The method of  claim 13 , wherein the oxidizing is by UV/ozone treatment or oxygen plasma treatment. 
     
     
         16 . The method of  claim 13 , wherein the reducing is by hot hydrogen treatment.