According to a news release from the National Renewable Energy Lab (NREL) in Golden, Colorado, researchers “have reported the first solar cell that produces a photocurrent that has an external quantum efficiency greater than 100 percent when photoexcited with photons from the high energy region of the solar spectrum.” What this means is that more energy is leaving the cell than is entering it. If this sounds a bit like “creating energy” to you, welcome to the club.
For a more scientific explanation, the “external quantum efficiency for photocurrent, usually expressed as a percentage, is the number of electrons flowing per second in the external circuit of a solar cell divided by the number of photons per second of a specific energy (or wavelength) that enter the solar cell.” What is significant about NREL’s announcement is that no solar cell had achieved 100 percent external quantum efficiency before now. According to the new release, NREL’s maximum efficiency was 114%.
Earlier this month, a paper on the topic was published in Science Magazine. The article explains that the efficiency was made possible by a process called Multiple Exciton Generation (MEG). NREL’s release says that MEG is a process “whereby a single absorbed photon of appropriately high energy can produce more than one electron-hole pair per absorbed photon.”
Kent Moors, of the Oil and Energy Investment Newsletter, argues that in order for “the new wave of MEG applications to make it to market, genuine global collaboration needs to take place.” However, he says, recent suit filed by US producers of photovoltaic cells against Chinese manufacturers has created an err of distrust and hinders collaboration.
Further advancements in solar technology will be integral to making it a viable, competitive energy source.