In research that has just been published in the journal Science, MIT researchers found that shining light on a sheet of graphene, treated so that it had two regions with different electrical properties, creates a temperature difference that, in turn, generates a current. Graphene heats inconsistently when illuminated by a laser, Jarillo-Herrero and his colleagues found.
Such differential heating has been observed before, but only under very special circumstances: either at ultralow temperatures (measured in thousandths of a degree above absolute zero), or when materials are blasted with intense energy from a high-power laser. This response in graphene, by contrast, occurs across a broad range of temperatures all the way up to room temperature, and with light no more intense than ordinary sunlight.
The research suggests graphene could be a very effective material for collecting solar energy, Jarillo-Herrero says, because it responds to a broad range of wavelengths; typical photovoltaic materials are limited to specific frequencies, or colors, of light. But more research will be needed, he says, adding, “It is still unclear if it could be used for efficient energy generation. It’s too early to tell.”
Philip Kim, an associate professor of physics at Columbia University who was not involved in this research, says the work represents “extremely important progress toward optoelectric and energy-harvesting applications” based on graphene. He adds that because of this team’s work, “we now have better understanding of photo-generated hot electrons in graphene, excited by light.”
The research was supported by the Air Force Office of Scientific Research, along with grants from the National Science Foundation and the Packard Foundation.