MIT’s Graphene Based Photovoltaic Cell.
László Forró, a professor at the Ecole Polytechnique Fédérale de Lausanne, in Switzerland, who was not associated with this research, says that the idea of using graphene as a transparent electrode was “in the air already,” but had not actually been realized. “In my opinion this work is a real breakthrough,” Forró says. “Excellent work in every respect.”
In what is likely to be one of the last graphene announcements of 2012, MIT’s news office highlighted MIT’s new type of flexible photovoltaic cell based on sheets of flexible graphene coated with a layer of low-cost zinc oxide nanowires. The value of this new development lies in a big low cost advantage over existing high cost silicon, indium-tin-oxide (ITO) photovoltaic cells. Both the high cost of high purity silicon and high cost, due to the limited supply of indium-tin-oxide, make MIT’s new graphene advance a serious contender in the development and deployment of low-cost, flexible PV solar cells for use on windows, roofs, electric vehicles, and many other surfaces. It’s easy to see quite why professor Laszlo Forro thinks this is a real breakthrough achievement by MIT.
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The new approach was published in the journal Nano Letters, in early December by lead co-authors MIT postdocs Hyesung Park and Sehoon Chang, and associate professor of materials science and engineering Silvija Gradečak, but only updated by MIT news right before Christmas on December 21. In addition to graphene zinc-oxide’s low cost advantage, MIT’s advance also offers a lower weight, better mechanical strength, and greater flexibility, according to MIT. Another advantage with this MIT approach, is that MIT’s process is a solution-based process that deposits zinc oxide nanowires on to the graphene electrodes and can be done entirely at temperatures below 175 degrees Celsius. Silicon solar cells are typically processed at significantly higher temperatures adding to the manufacturing cost.
“Gradečak cautions that while the scalability for solar cells hasn’t been demonstrated yet — she and her colleagues have only made proof-of-concept devices a half-inch in size — she doesn’t foresee any obstacles to making larger sizes. “I believe within a couple of years we could see [commercial] devices” based on this technology, she says.”
A good way to end the year on in graphene research. Onward and upward in 2013.
Graphene Cathode-Based ZnO Nanowire Hybrid Solar Cells
Growth of semiconducting nanostructures on graphene would open up opportunities for the development of flexible optoelectronic devices, but challenges remain in preserving the structural and electrical properties of graphene during this process. We demonstrate growth of highly uniform and well-aligned ZnO nanowire arrays on graphene by modifying the graphene surface with conductive polymer interlayers. On the basis of this structure, we then demonstrate graphene cathode-based hybrid solar cells using two different photoactive materials, PbS quantum dots and the conjugated polymer P3HT, with AM 1.5G power conversion efficiencies of 4.2% and 0.5%, respectively, approaching the performance of ITO-based devices with similar architectures. Our method preserves beneficial properties of graphene and demonstrates that it can serve as a viable replacement for ITO in various photovoltaic device configurations.
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