Scientists demonstrate high-efficiency quantum dot solar cells

Scientists from the National Renewable Energy Laboratory (NREL) have demonstrated the first solar cell with external quantum efficiency (EQE) exceeding 100 percent for photons with energies in the solar range. (The EQE is the percentage of photons that get converted into electrons within the device.) The researchers will present their findings at the AVS 59th International Symposium and Exhibition, held Oct. 28 — Nov. 2, in Tampa, Fla.

While traditional semiconductors only produce one electron from each photon, nanometer-sized crystalline materials such as quantum dots avoid this restriction and are being developed as promising photovoltaic materials. An increase in the efficiency comes from quantum dots harvesting energy that would otherwise be lost as heat in conventional semiconductors. The amount of heat loss is reduced and the resulting energy is funneled into creating more electrical current.

By harnessing the power of a process called multiple exciton generation (MEG), the researchers were able to show that on average, each blue photon absorbed can generate up to 30 percent more current than conventional technology allows. MEG works by efficiently splitting and using a greater portion of the energy in the higher-energy photons. The researchers demonstrated an EQE value of 114 percent for 3.5 eV photons, proving the feasibility of this concept in a working device.

Joseph Luther, a senior scientist at NREL, believes MEG technology is the right direction. “Since current solar cell technology is still too expensive to completely compete with non-renewable energy sources, this technology employing MEG demonstrates that the way in which scientists and engineers think about converting solar photons to electricity is constantly changing,” Luther said. “There may be a chance to dramatically increase the efficiency of a module, which could result in solar panels that are much cheaper than non-renewable energy sources.”

MORE INFORMATION ABOUT THE AVS 59th INTERNATIONAL SYMPOSIUM & EXHIBITION

The Tampa Convention Center is located along the Riverwalk in the heart of downtown Tampa at 333 S. Franklin St., Tampa, Florida, 33602.

USEFUL LINKS:

Main meeting website: http://www2.avs.org/symposium/AVS59/pages/greetings.html

Technical Program: http://www.avssymposium.org/

Housing and Travel Information: http://www2.avs.org/symposium/AVS59/pages/housing_travel.html

PRESS REGISTRATION

The AVS Pressroom will be located in the Tampa Convention Center. Your complimentary media badge will allow you to utilize the pressroom to write, interview, collect new product releases, review material, or just relax. The media badge will also admit you, free of charge, into the exhibit area, lectures, and technical sessions, as well as the Welcome Mixer on Monday evening and the Awards Ceremony and Reception on Wednesday night. Pressroom hours are Monday-Thursday, 8-5 p.m.

To register, please contact:

Della Miller, AVS
E-mail: della@avs.org
This news release was prepared for AVS by the American Institute of Physics (AIP).

ABOUT AVS

Founded in 1953, AVS is a not-for-profit professional society that promotes communication between academia, government laboratories, and industry for the purpose of sharing research and development findings over a broad range of technologically relevant topics. Its symposia and journals provide an important forum for the dissemination of information in many areas of science and technology, enabling a critical gateway for the rapid insertion of scientific breakthroughs into manufacturing realities.