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.
FULL DETAILS FROM NREL WEBSITE
The Energy technology Partnership (ETP) have announced they are able to offer up to 20 studentships in 2012, specifically related to the areas of:
• Wind energy;
• Marine energy;
• Solar energy;
• Energy conversion and storage;
• Energy materials;
• Grid and networks;
• Energy utilisation in buildings;
• Carbon Capture and Storage.
Download GUIDANCE NOTES to learn more about the programme, deadline for submission and application requirements.
More details at ETP WEBSITE.
California-based Alta devices today announces results of PV tests where they claim their engineers have achieved 27.6 percent efficiency last year and later hit 28.2 percent efficiency. Both results were verified by the National Renewable Energy Laboratory and are more than one percent higher than previous efficiency records for single-junction solar cells.
The company did not indicate when it expects to have a commercial product, but executives said that the work it has done on capturing light emitted by solar cells can be applied by other researchers in the field who are struggling to push the limits of solar cell efficiency.
The solar cell material the company is working with is gallium arsenide (GaAs), the type often used in high-performance solar devices with several layers of semiconductors, such as those used on satellites or concentrating solar photovoltaic generators.
Alta Devices announcment
From the 1st of August 2011, new entrants into the FIT scheme will receive amended tariffs as set out below:
>50 kW – ≤ 150 kW Total Installed Capacity (TIC) – 19.0p/ kWh
>150 kW – ≤ 250 kW TIC – 15.0p/ kWh
250 kW – 5 MW TIC and stand-alone installations – 8.5p/ kWh
≤ 250 kW – 14.0p/ kWh
>250 kW – ≤ 500 kW – 13.0p/ kWh
DECC say “Over 500 responses were received and carefully analysed before a decision was made regarding the change in tariffs. The fast track review showed that the number of planned larger PV projects is much higher than originally expected. Without urgent action, the scheme would have been overwhelmed within a very short period of time. Every 5 MW large scale solar scheme would incur a cost of approximately £1.3 million per year, which means that 20 such schemes would incur an annual cost of around £26 million, money that could support PV installations for over 25,000 households.
The changes, to take effect from 1st August for new installations and subject to Parliamentary and State aid clearance, will help manage the finances of the Feed-in Tariffs to ensure value for money for the consumer and to help protect the scheme in the future. Solar schemes under 50kW are unaffected by this review.”
Full announcement available on DECC website