Nanoparticles could prompt a new generation of outdoor solar cells that may replace the traditional. A team from the Edward S. Rogers Sr. Department of Electrical and Computer Engineering at the University of Toronto — in collaboration with Dalhousie University, King Abdullah University of Science and Technology and Huazhong University of Science and Technology — has designed a class of solar-sensitive nanoparticles that they say outperforms traditional solar cells. Called colloidal quantum dots, the new solid, stable nanoparticles could allow for more flexible solar cells, as well as better gas sensors, infrared lasers and infrared light emitting diodes. Tiny colloidal quantum dots used to collect sunlight are dependent on typical electron-rich n-type semiconductors and electron-deficient p-type semiconductors. Traditionally, the n-type give up electrons as they attach to oxygen atoms and turn into p-type semiconductors. To overcome this problem, the new colloidal quantum dot n-type material has been designed to not bind with oxygen when exposed to air, which allows the two types of semiconductors to remain stable simultaneously and separate from each other. According to the researchers, this enhances light absorption and demonstrates potential for new optoelectronic devices that use light and electric properties. This could lead to more sophisticated weather satellites, remote controls, satellite communication and pollution detectors. The new semiconductor material has demonstrated solar power conversion efficiency of up to eight percent, the researchers have found. Further study is needed as the researchers agree that the quantum dots could be mixed into ink and painted or printed onto thin, flexible surfaces such as roofing shingles. This could lower the cost and accessibility of solar power. “The field of colloidal quantum dot photovoltaics requires continued improvement in absolute performance, or power conversion efficiency,” said Ted Sargent, one of the lead researchers and a professor at the University of Toronto. “The field has moved fast and keeps moving fast.” The research was published in Nature Materials (doi: 10.1038/nmat4007). For more information, visit www.utoronto.ca.