Jun 23 2010
Recently, a team of researchers led by the University of Minnesota has overcome a major barrier in the effort to develop solar cells that offer twice the level of efficiencies as present levels.
The research team has created a new window of opportunity for other solar cell researchers pursuing to develop efficient, cost-effective solar energy devices, by demonstrating how power that is currently lost from semiconductors of solar cells can be harnessed and supplied to electric circuits. A system developed on this research can reduce the cost of producing solar cells.
The research is the result of six years of hard work that commenced at the University Institute of Technology (formerly College of Science and Engineering) by professors David Norris, Eray Aydil and Xiaoyang Zhu (presently with the University of Texas-Austin), headed by William Tisdale, an University of Minnesota graduate student.
In the majority of solar cells presently being used, sunlight strikes the topmost portion of the solar cells, which are composed of a crystalline semiconductor material, generally silicon. One commonly occurring problem is that most electrons contained in the silicon absorb surplus solar energy and radiate back that energy as heat even before that heat can be harnessed.
An earlier initiative in trapping that energy is to move these “hot electrons” from the semiconductor into an electric circuit, before the electrons cool off. However, efforts to harness “hot” electrons have not succeeded.
Nevertheless, the properties of semiconductors change when they are built in tiny pieces in the scale of few nanometers. Tisdale and his team highlighted that quantum dots, comprised of selenide, can be trapped of their “hot” electrons before the electrons are cooled. These electrons can be harnessed by titanium dioxide, which is an abundant, inexpensive semiconductor material. The research shows that solar cells with 66% efficiency levels can be achieved.
Source: http://www.umn.edu/