Awards Database

Scialog: Collaborative Teams - 2013

Chito Kendrick

Colorado School of Mines

Joan Redwing

Science and Engineering, Pennsylvania State University, University Park

Adele Tamboli

Physics, Colorado School of Mines

Eric Toberer Toberer

Physics, Colorado School of Mines

Silicon Diselenide: A 1.7 eV Solar Absorber for Tandem Silicon Photovoltaics

When it comes to producing electricity directly from sunlight, crystalline silicon wafers are relatively cheap and fairly efficient compared with many other materials. But efforts continue to improve efficiencies in order to increase the demand for solar energy and provide a cost- effective clean alternative to pollution-causing fossil fuels. Even small increases in the efficiency of solar cells could go a long way toward making them affordable sources of renewable energy. The ultimate goal of photovoltaics research is to reduce the technology’s price per kilowatt-hour and make solar energy competitive with fossil fuels. According to the U.S. Department of Energy’s SunShot initiative:
When the price of solar electricity reaches about $0.06 per kilowatt-hour over its lifetime, it will be cost-competitive with other non-renewable forms of electricity. This in turn will enable solar-generated power to grow from less than .05% of the current electricity supply to roughly 14% by 2030 and 27% by 2050. Source: http://www1.eere.energy.gov/solar/sunshot/about.html
This two-year research project is being conducted by investigators from the Colorado School of Mines physics department—Chito Kendrick, Adele Tamboli and Eric Toberer—and Joan Redwing, from the materials science and engineering department at Penn State University. Tamboli is also a staff scientist at the National Renewable Energy Laboratory (NREL) in Golden, Colorado. The researchers will be exploring the use of crystalline silicon diselenide (SiSe2) as a thin film to sit atop a more conventional solar cell. Their work involves determining how best to synthesize the material into an ultra-thin film, as well as how to “dope” the material, that is, alter its electrical characteristics, to improve its photovoltaic qualities. The researchers selected silicon diselenide to work with because of its “band gap” – the amount of energy, expressed in electron volts (eV), needed to kick out an electron from an atom or molecule in the process of creating electrical current. Crystalline silicon has a relatively low band gap of about 1.1 eV, which means much of the higher energy photons in sunlight are lost as useless heat. Silicon diselenide, however, has a band gap of about 1.7 eV, meaning it can absorb higher energy photons without generating additional waste heat, making use of more of the solar spectrum and thereby increasing efficiency.

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