Carbon-based Solar Cells
Solar panels need silicon for absorption of light. Silicon doesn’t come cheap.This cost-factor is preventing people from using solar energy on a large scale. Scientists utilize another substance i.e. ruthenium for solar cells. Rutheniumcan is cheaper than silicon but ruthenium is a rare metal on Earth. It is as rare as platinum. Naturally it can’t be available for mass production. Compared to silicon, carbon is cheap and abundant. The graphene, another form of carbon, is capable of absorbing a wide range of light frequencies.
Graphene is a single sheet of carbon, one atom thick. Graphene has potential to be utilized as an effective, less toxic and cheaper than other alternatives for solar cells. Chemists at Indiana University Bloomington are trying to come up with a better alternative than silicon. If successful, this can be a path breaking discovery.
Other people too took this initiative of using carbon sheets for solar power. But they encountered some hurdles. They used the graphene form of carbon for solar cells. Grephene is akin to graphite used in pencil lead. Graphene absorbs a wide range of light frequencies. Scientists have found large sheets of graphene to be too unmanageable to work with. Large sheets are sticky and get attached with other sheets. Now Indiana University Bloomington researchers are trying to deal with this problem. They are trying to develop non-sticky graphene sheets that are stable. They are putting their efforts on “attaching a semi-rigid, semi-flexible, three-dimensional sidegroup to the sides of the graphene.” They know how to derive energy from carbon. Now chemists from Indiana University Bloomington are graduating to the next logical step i.e. conversion of that energy into electricity. If everything will turn out alright then carbon can be an alternative to expensive silicon and ruthenium, which is as rare as platinum.
Chemists and engineers kept on trying to work out a solution for the stickiness of graphene. They devised many methods for keeping single graphene sheets separate. Till now the most effective solution prior to the Indiana University Bloomington scientists’ experiment has been breaking up graphite (top-down) into sheets and wrap polymers around them. But this method has its own disadvantage. Those graphene sheets are too large for light absorption for solar cells. Indiana University chemists devised a completely new method for carbon sheets. They utilized a 3-D bramble patch between the carbon sheets. This method helped the scientists to dissolve sheets containing as many as 168 carbon atoms. They are successful in making the graphene sheets from smaller molecules (bottom-up) so that they are uniform in size. Till now, it is the biggest stable graphene sheet ever made with the bottom-up approach. Chemist Liang-shi Li, who led the research, tells us, “Our interest stems from wanting to find an alternative, readily available material that can efficiently absorb sunlight. At the moment the most common materials for absorbing light in solar cells are silicon and compounds containing ruthenium. Each has disadvantages.”
Li is of the opinion, “Harvesting energy from the sun is a prerequisite step. How to turn the energy into electricity is the next. We think we have a good start.” Other members of the project team are Ph D students Xin Yan and Xiao Cui and postdoctoral fellow Binsong Li. This project is financed by the National Science Foundation and the American Chemical Society Petroleum Research Fund.