NSF-funded project aims to grab more sun for solar cells

Image depicts the process to be used
A) A higher energy photon creates an electron-hole pair in a wide gap absorber. B) The junction electric field drives the carriers into the narrower gap host material, where one of them decays by impact ionization. C) The photon effectively creates two electrons and two holes in the host material, where they are mobile and ready for collection. (Courtesy of Stephen Kevan) ... click on image for a larger view

EUGENE, Ore. -- (Aug. 30, 2010) -- Researchers from three institutions are uniting under a three-year, $1.6 million grant from the National Science Foundation to boost the juice of solar cells.

Under the project researchers will seek to design new semiconductor structures that "will overcome the current limit on efficiency of most solar cells in which each light particle captured by the sun only provides one electron of electrical current," said Stephen Kevan, head of physics at the University of Oregon and the project's principle investigator. "If our efforts succeed, we will significantly improve solar cell efficiency using environmentally benign materials."

The grant, which begins Sept. 1, comes from the NSF's Directorate for Mathematical and Physical Sciences as part of its Solar Energy Initiative.

Geraldine Richmond, professor of chemistry at the UO, and Malgorzata Peszynska, professor of mathematics at Oregon State University, are co-principal investigators on the project. An expert in the growth of thin films, Angus Rockett, associate head of materials science and engineering at the University of Illinois at Urbana-Champaign, also will have an important role in the project.

Multiple laboratories at the UO, OSU and Illinois will be used in device design, development and optimization, including the Center for Advanced Materials Characterization in Oregon (CAMCOR), which is located in the UO's underground Lokey Laboratories. "We are exploring promising combinations of semiconducting materials with appropriate band alignment and growth characteristics to promote more efficient impact ionization," Kevan said.

The goal is to design nanostructured semiconducting materials that convert and channel sunlight into useful electrical energy rather than into waste heat. The principle behind the new process, called heterojunction-assisted impact ionization, is that shorter wavelength photons will be absorbed to capture a higher ratio of electrons, providing for higher electrical currents and a reduction of energy loss.

Three additional collaborators in the project are: Dave Cohen, professor of physics at the UO, who, like Rockett, has extensive experience working on photovoltaic materials including thin films; Janet Tate, a solid-state physicist at OSU with expertise in growing thin-film electronic and optical materials; and Guenter Schneider is a solid-state theorist at OSU who will work closely with Peszynska to model potential new devices and predict new target structures.

Kevan, Cohen, Richmond and Tate also are member faculty of the Oregon Built Environment & Sustainable Technologies Center (Oregon BEST), a nonprofit organization established by the Oregon Legislature to commercialize and transform sustainable built environment and renewable energy research into on-the-ground products, services and jobs. In 2009, Oregon BEST funding established the Photovoltaics Characterization Laboratory, a shared user facility that is part of the Support Network for Research and Innovation in Solar Energy (SuNRISE), a collaborative solar energy laboratory based at the UO.

More information, including a video, about the newly funded project led by Kevan can be found in a news feature on the Oregon BEST website.