Currently 40% of the solar energy that reaches Earth lies in the near-infra-red region of the spectrum, and while most photovoltaic devices are unable to harness this energy, a team at MIT has created an all-carbon solar cell that absorbs this infra-red heat radiation. The team believe that their all-carbon solar cell will lead to the development of combination solar cells, that use both traditional silicon-based cells and the new all-carbon cells to generate even more energy!
Like many recent energy breakthroughs, the answer lies in carbon nanotubes. The team has used nanotubes and an exotic form of carbon called C60 to make their new cell. In the journal Advanced Materials, Professor of Chemical Engineering at MIT and senior author Michael Strano said: “It’s a fundamentally new kind of photovoltaic cell. It has only been within the last few years or so that it has been possible to hand someone a vial of just one type of carbon nanotube.”
Of course to make the cell work as efficiently as possible, the nanotubes have to be very pure, and of a uniform type: single-walled. Traditional PV cells only use a layer of polymer to hold the nanotubes in position and collect the electrons knocked loose when they absorb sunlight. However the new process sees extra coatings added in order to prevent degradation with exposure to air allowing the new all-carbon PV cell to be as stable as possible.
As the material is transparent to visible light, such carbon cells can be placed over conventional solar cells to capture infra-red ways. These tandem devices will then be able to harness most of the energy’s sunlight, however the technology is far from ready. In their research notes, Strano notes their current models only have an energy-conversion efficiency of only about 0.1%!