Photovoltaic cells having electrical contacts formed from metal nanoparticles and methods for production thereof

Abstract

Photovoltaic cells having copper contacts can be made by using copper nanoparticles during their fabrication. Such photovoltaic cells can include a copper-based current collector located on a semiconductor substrate having an n-doped region and a p-doped region. The semiconductor substrate is configured for receipt of electromagnetic radiation and generation of an electrical current therefrom. The copper-based current collector includes an electrically conductive diffusion barrier disposed on the semiconductor substrate and a copper contact disposed on the electrically conductive diffusion barrier. The copper contact is formed from copper nanoparticles that have been at least partially fused together. The electrically conductive diffusion barrier limits the passage of copper therethrough.

What is claimed is the following: 
     
         1 . A photovoltaic cell comprising:
 a copper-based current collector located on a semiconductor substrate, the copper-based current collector comprising:
 an electrically conductive diffusion barrier disposed on the semiconductor substrate, the electrically conductive diffusion barrier limiting the passage of copper therethrough; and 
 a copper contact disposed on the electrically conductive diffusion barrier, the copper contact being formed from copper nanoparticles that have been at least partially fused together; 
 wherein the semiconductor substrate comprises an n-doped region and a p-doped region, and the semiconductor substrate is configured for receipt of electromagnetic radiation and generation of an electrical current therefrom. 
   
     
     
         2 . The photovoltaic cell of  claim 1 , wherein the copper-based current collector is located on a face of the photovoltaic cell that receives the electromagnetic radiation. 
     
     
         3 . The photovoltaic cell of  claim 1 , wherein the copper-based current collector is located on a face of the photovoltaic cell opposite a face of the photovoltaic that receives the electromagnetic radiation. 
     
     
         4 . The photovoltaic cell of  claim 1 , wherein the copper-based current collector is in contact with the n-doped region of the semiconductor substrate. 
     
     
         5 . The photovoltaic cell of  claim 4 , further comprising:
 an electrical connection in contact with the p-doped region of the semiconductor substrate.   
     
     
         6 . The photovoltaic cell of  claim 1 , wherein the semiconductor substrate comprises a silicon substrate. 
     
     
         7 . The photovoltaic cell of  claim 6 , wherein the electrically conductive diffusion barrier is selected from the group consisting of TiN, TaN, WN, TiW, W and any combination thereof. 
     
     
         8 . The photovoltaic cell of  claim 7 , wherein the electrically conductive diffusion barrier is formed from nanoparticles that have been at least partially fused together. 
     
     
         9 . The photovoltaic cell of  claim 1  wherein the copper contact further comprises a corrosion-resistant substance. 
     
     
         10 . The photovoltaic cell of  claim 9 , wherein a corrosion-resistant coating is disposed on the copper contact, the corrosion-resistant coating being selected from the group consisting of a Sri coating, an Ag coating, a SnAgCu coating, an Al coating, a Si coating, a polymer coating, and any combination thereof. 
     
     
         11 . The photovoltaic cell of  claim 1 , wherein the copper nanoparticles are mixed with micron-scale copper particles while being formed into the copper contact. 
     
     
         12 . The photovoltaic cell of  claim 1 , wherein the copper contact further comprises a conductive additive selected from the group consisting of carbon black, pyrene, phenanthrene, carbon nanotubes, graphene, and any combination thereof. 
     
     
         13 . The photovoltaic cell of  claim 12 , wherein the conductive additive is mixed with the copper nanoparticles while being formed into the copper contact. 
     
     
         14 . The photovoltaic cell of  claim 12 , wherein the conductive additive is disposed on the copper contact. 
     
     
         15 . The photovoltaic cell of  claim 1 , further comprising:
 antireflective coating disposed on a face of the semiconductor substrate that receives the electromagnetic radiation.   
     
     
         16 . A method for forming a photovoltaic cell, the method comprising:
 applying an electrically conductive diffusion barrier onto a semiconductor substrate comprising an n-doped region and a p-doped region, the electrically conductive diffusion barrier limiting the passage of copper therethrough;   applying copper nanoparticles onto the electrically conductive diffusion barrier; and   heating the copper nanoparticles to a temperature sufficient to at least partially fuse the copper nanoparticles together, thereby forming a copper contact on the electrically conductive diffusion barrier.   
     
     
         17 . The method of  claim 16 , wherein the electrically conductive diffusion barrier and the copper contact are disposed on the n-doped region of the semiconductor substrate. 
     
     
         18 . The method of  claim 16 , wherein the copper nanoparticles are applied to the electrically conductive diffusion barrier as a dispensible nanoparticle paste formulation comprising an organic matrix in which the copper nanoparticles are dispersed. 
     
     
         19 . The method of  claim 18 , wherein at least a portion of the copper nanoparticles are about 20 nm in size or smaller. 
     
     
         20 . The method of  claim 18 , wherein the dispensible nanoparticle paste formulation further comprises micron-scale copper particles, a conductive additive, a corrosion-resistant substance, or any combination thereof. 
     
     
         21 . The method of  claim 16 , wherein the semiconductor substrate comprises a silicon substrate. 
     
     
         22 . The method of  claim 21 , wherein the electrically conductive diffusion barrier is selected from the group consisting of TiN, TaN, WN, TiW, W and any combination thereof. 
     
     
         23 . The method of  claim 22 , wherein the electrically conductive diffusion barrier is applied to the semiconductor substrate by plating, physical vapor deposition, or chemical vapor deposition. 
     
     
         24 . The method of  claim 22 , further comprising:
 applying a plurality of nanoparticles to the semiconductor substrate; and   at least partially fusing the nanoparticles together to form the electrically conductive diffusion barrier.   
     
     
         25 . The method of  claim 16 , further comprising:
 adhering the semiconductor substrate to a surface while at least partially fusing the copper nanoparticles together.