news digest ♦ Solar
Yablonovitch. “Based on performance, it is the ideal material for making solar cells.”
Past efforts to boost the conversion efficiency of solar cells focused on increasing the number of photons that a cell absorbs. Absorbed sunlight in a solar cell produces electrons that must be extracted from the cell as electricity. Those electrons that are not extracted fast enough, decay and release their energy. If that energy is released as heat, it reduces the solar cell’s power output. Miller’s calculations showed that if this released energy exits the cell as external fluorescence, it would boost the cell’s output voltage.
“This is the central counter-intuitive result that permitted efficiency records to be broken,” Yablonovitch says.
based on GaAs that not only smashed previous solar conversion efficiency records, but can be produced at well below the cost of any other solar cell technology. Alta Devices expects to have GaAs solar panels on the market within a year.
“The SQ Limit is still the foundation of solar cell technology,” says Yablonovitch. “However, the physics of light extraction and external fluorescence are clearly relevant for high performance solar cells.”
Yablonovitch believes that the theoretical work by the group, in combination with the performance demonstrations at Alta Devices, could dramatically change the future of solar cells.
“We’re going to be living in a world where solar panels are very cheap and very efficient,” Yablonovitch says.
This research was funded by a grant from DOE’s Light-Material Interactions in Energy Conversion Energy Frontier Research Centre (LMI-EFRC).
Further details of this work have been published in the paper, “Intense Internal and External Fluorescence as Solar Cells Approach the Shockley-Queisser Efficiency Limit,” by Miller et al, published online: arXiv:1106.1603v3 [physics. optics]
Thin film solar cells fabricated from gallium arsenide have achieved a record sunlight-to- electricity conversion efficiency of 28.4 percent. (Image courtesy of Alta Devices, Inc.)
As Miller explains, “In the open-circuit condition of a solar cell, electrons have no place to go so they build up in density and, ideally, emit external fluorescence that exactly balances the incoming sunlight. As an indicator of low internal optical losses, efficient external fluorescence is a necessity for approaching the SQ Limit.”
Using a single-crystal thin film technology developed earlier by Yablonovitch, called “epitaxial liftoff,” Alta Devices was able to fabricate solar cells
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www.compoundsemiconductor.net November/December 2011
First Solar commences construction on Australia’s first utility-scale solar farm
The project, which involves the use of the firm’s cadmium telluride solar modules, will support local businesses and boost the economy in Western Australia.
First Solar has commenced construction on the 10- MW AC Greenough River Solar Farm, located 50km south of Geraldton.
Once completed, the CdTe solar farm will be the first utility-scale photovoltaic (PV) project in Australia and will bring significant investment to the local community through a partnership with local civil contractor WBHO Civil - the company awarded
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