A collaboration between the US Army Research Laboratory (ARL) and State University of New York (SUNY) at Buffalo has led to the potential to boost the efficiency of quantum dot solar cells by a factor of two. The discovery could lead to lighter loads for soldiers in the field, to lighter solar devices and to a reduction in commercial production costs. Quantum dots, discovered in the 1980s, are portions of matter, or semiconductors, with characteristics similar to the size and shape of the individual crystal. (Images: ARL) Quantum dots are a kind of semiconductor whose electronic characteristics resemble that of an individual crystal. The bandgaps inside a quantum dot can be tuned by changing the size of the dot. The tunable bandgap makes them an excellent component for solar cells because the bandgap could be theoretically optimized to create a superefficient photovoltaic cell. Their size also determines what frequency of light they can emit. The ARL team selectively doped (added impurities) quantum dots to create potential barriers around them and, together with SUNY researchers, solved the problem of recombination losses and the degradation of device performance associated with introducing dots into the gaps of solar cell structures. Increasing the efficiency of solar cells by using quantum dots means that solar cells can be smaller with the same efficiency as ones used now, a life-saving factor for soldiers stationed abroad. It also would drive down production prices in the commercial market because mass-produced quantum dots can be fairly inexpensive. Parvex Uppal, Electro-Optic/Infrared Materials and Devices Branch chief at ARL's Sensors and Electrons Devices Directorate (SEDD), said that whenever there is the potential to decrease the size of a solar battery charger or replace a heavier energy source for a lighter one, there are significant implications for the soldier, for the US Department of Defense and for the commercial market. US Army Research Laboratory scientist Kimberly Sablon proposed a modification to the structure of quantum dots that led to the discovery that quantum dots could be almost twice as efficient. Kimberly Sablon, a research scientist with the Energy Conversion Team, Electro-optic/Infrared Materials and Devices Branch, whose idea it was to minimize quantum dot recombination losses to raise solar cell efficiency, is already working on the next step. "The quantum dot research findings give people hope about the direction. There is so much more opportunity to make the transition toward solar use." For more information, visit: www.arl.army.mil For another research perspective on using quantum dots in solar cells, see: QDs Improve Next-Gen Solar Cells by 6%