Efficient and Economical Graphite-Based Photovoltaic Cells


Background: Photovoltaic cells convert sunlight directly into electricity through the interaction of photons and electrons in a photoconducting material. The major barriers to widespread solar cell use are low efficiency and high cost per watt. A UW-Madison researcher previously developed an efficient photovoltaic cell based on single-walled carbon nanotubes (see WARF reference number P04002US); however it may be difficult to produce these cells inexpensively. Technology Description: UW-Madison researcher have now used lithographically patterned thick stacks of carbon nanoribbons as the building blocks of an efficient and economical photovoltaic cell. The basic design of the cell includes several spatially separated graphite nanoblocks each composed of many layers of graphite. The graphite is nanopatterned to mimic vertically stacked nanoribbons which bridge electrically conductive contacts. The electronic properties of the patterned nanoribbons depend on the direction and width of the nanoribbons much like the electronic properties of single-walled carbon nanotubes. In fact a nanoribbon may be thought of as an unrolled nanotube. By incorporating nanoribbons with different widths into the photovoltaic cell the cell can be designed to absorb efficiently across the solar spectrum. However unlike nanotubes when carbon nanoribbons of different sizes are put in contact with a metal lead approximately the same potential is generated at all the contacts regardless of nanoribbon size. As a result nanoribbons and nanoribbon stacks don’t need to be sorted during the production process making nanoribbon-based solar cells easier to design and manufacture than nanotube-based cells. Applications: 1) Photovoltaic cells 2) Solar power Opportunity for collaboration: The Wisconsin Alumni Research Foundation (WARF) is seeking commercial partners interested in developing an efficient and economical photovoltaic cell.


1) Efficient and less expensive to manufacture than carbon nanotube-based photovoltaic cells 2) May decrease production costs to less than 50 cents per watt 3) cells can be wired to increase the current or the voltage just like in a conventional photovoltaic cell 4) cells can be made using semiconductor processing techniques such as lithography patterning and etching providing an inexpensive parallel process capable of making many nanoribbon stacks in a single run

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