NREL Scientists report first experiment to show effieciency of 100-percent-plus in operating solar cells.

NREL Scientists Report First Solar Cell Producing More Electrons In Photocurrent Than Solar Photons Entering Cell. Researchers from the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) have reported on testing a solar cell that produces a photocurrent that has an external quantum efficiency greater than 100 percent when photoexcited with photons from the high energy region of the solar spectrum.

They claim in their experiments external quantum efficiency reached a peak value of 114 percent. The newly reported work marks a promising step toward developing Next Generation Solar Cells for both solar electricity and solar fuels that will be competitive with, or perhaps less costly than, energy from fossil or nuclear fuels.

The paper states “Multiple Exciton Generation is key to making it possible”. It appears in the Dec. 16 issue of Science Magazine. Titled “Peak External Photocurrent Quantum Efficiency Exceeding 100 percent via MEG in a Quantum Dot Solar Cell”, it is co-authored by NREL scientists Octavi E. Semonin, Joseph M. Luther, Sukgeun Choi, Hsiang-Yu Chen, Jianbo Gao, Arthur J. Nozikand Matthew C. Beard. The research was supported by the Center for Advanced Solar Photophysics, an Energy Frontier Research Center funded by the DOE Office of Science, Office of Basic Energy Sciences. Semonin and Nozik are also affiliated with the University of Colorado at Boulder.

They explain the mechanism for producing a quantum efficiency above 100 percent with solar photons is based on a process called Multiple Exciton Generation (MEG), whereby a single absorbed photon of appropriately high energy can produce more than one electron-hole pair per absorbed photon. The researchers achieved the 114 percent external quantum efficiency with a layered cell consisting of antireflection-coated glass with a thin layer of a transparent conductor, a nanostructured zinc oxide layer, a quantum dot layer of lead selenide treated with ethanedithol and hydrazine, and a thin layer of gold for the top electrode.

Such potentially highly efficient cells, coupled with their low cost per unit area, are called Third (or Next) Generation Solar Cells. Present day commercial photovoltaic solar cells are based on bulk semiconductors, such as silicon, cadmium telluride, or copper indium gallium (di)selenide; or on multi-junction tandem cells drawn from the third and fifth (and also in some cases fourth) columns of the Periodic Table of Elements. All of these cells are referred to as First- or Second-Generation Solar Cells.


New developments in Lithium rechargable SSFC from MIT

Researchers at MIT, led by Dr. Yet-Ming Chiang (co-founder of A123 Systems), have reported on their development of a new energy storage concept.

They have been working on a semi-solid flow cell (SSFC) combining the high energy density of rechargeable lithium batteries with the flexible and scalable architecture of fuel cells and flow batteries – they claim it offers energy densities an order of magnitude greater than previous flow batteries giving possible applications in transportation and grid-scale storage

They are still working-through some issues but have published some details of their work – see the link below….

SSFC development by MIT

Solid Waste Powered Hydrogen Fuel Cell Demonstration

Canadian fuel specialist, Ballard Power Systems, has partnered with GS Platech a subsidiary of GS Caltex – one of South Korea’s largest petroleum refiners – to produce hydrogen from municipal solid waste to power zero-emission fuel cells.

GS Platech’s pilot plant in Cheongsong, South Korea is capable of treating 5 tons (4.53 tonnes) of organic solid waste per day using plasma gasification technology, and producing sufficient high purity hydrogen to generate 50 kW of clean power.

Ballard will supply the fuel cell generator, based on its Dantherm Power DBX5000 technology. The partnership claims that this will be the first demonstration of a waste to energy solution incorporating these technologies together.

This will be the first demonstration of a waste-to-energy solution incorporating these technologies together. Upon successful demonstration of the solution, GS Platech intends to further promote it to new customers worldwide.

The treatment of municipal solid waste is a growing problem in many nations, including Asia Pacific countries with particularly high population densities such as China, India, Korea, Japan and Singapore. This solution can potentially allow municipalities to address two key environmental issues in tandem:environmentally responsible waste treatment as well as clean power production.

Link to the full news release