In a paper published in a May issue of the American Chemical Society's Nano Letters journal, an NREL team found that tiny nanocrystals, also known as quantum dots, produce as many as three electrons from one high energy photon of sunlight. When today's photovoltaic solar cells absorb a photon of sunlight, the energy gets converted to at most one electron, and the rest is lost as heat.
The research demonstrates the potential for solar, or photovoltaic, cells that reduce wasteful heat and maximize the amount of the sun's energy that is converted to electricity - a key step toward making solar energy more cost-competitive with conventional power sources.
The NREL research team, led by Arthur Nozik, worked in collaboration with the Naval Research Laboratory (NRL) in Washington, D.C.
The findings are further confirmation of pioneering work by Nozik, who in 2000 predicted that quantum dots could increase the efficiency of solar cells through a process now termed multiple exciton generation or MEG. Last year, Richard Schaller and Victor Klimov of Los Alamos National Laboratory in New Mexico were the first to demonstrate the electron multiplication phenomenon predicted by Nozik, using quantum dots made from lead selenide.
"We have shown that solar cells based on quantum dots theoretically could convert more than 65 percent of the sun's energy into electricity, approximately doubling the efficiency of solar cells," Nozik said. The best cells today convert about 33 percent of the sun's energy into electricity.
Publication date: 06/13/2005