Good work for NREL. It seems ground solar cells move forward. With 4.6 kilograms
of glass cover slides and other mass add-ons for launch, the very efficient
cells have very low power density. Tits on a bull for SBSP.

markreiff wrote:
> FYI,
> "NREL Solar Cell Sets World Efficiency Record at 40.8 Percent"
> National Renewable Energy Laboratory
> http://www.nrel. gov/news/ press/2008/ 625.html
> : Scientists at the U.S. Department of Energy's National Renewable
> : Energy Laboratory (NREL) have set a world record in solar cell
> : efficiency with a photovoltaic device that converts 40.8 percent of
> : the light that hits it into electricity. This is the highest
> : confirmed efficiency of any photovoltaic device to date.
> : The inverted metamorphic triple-junction solar cell was designed,
> : fabricated and independently measured at NREL. The 40.8 percent
> : efficiency was measured under concentrated light of 326 suns. One
> : sun is about the amount of light that typically hits Earth on a
> : sunny day. The new cell is a natural candidate for the space
> : satellite market and for terrestrial concentrated photovoltaic
> : arrays, which use lenses or mirrors to focus sunlight onto the
> : solar cells.
> : The new solar cell differs significantly from the previous record
> : holder – also based on a NREL design. Instead of using a germanium
> : wafer as the bottom junction of the device, the new design uses
> : compositions of gallium indium phosphide and gallium indium
> : arsenide to split the solar spectrum into three equal parts that
> : are absorbed by each of the cell's three junctions for higher
> : potential efficiencies. This is accomplished by growing the solar
> : cell on a gallium arsenide wafer, flipping it over, then removing
> : the wafer. The resulting device is extremely thin and light and
> : represents a new class of solar cells with advantages in
> : performance, design, operation and cost.
> : NREL's Mark Wanlass invented the original inverted cell, which
> : recently won a R&D 100 award. His design was modified by a team led
> : by John Geisz that further optimized the junction energies by
> : making the middle junction metamorphic as well as the bottom
> : junction. Metamorphic junctions are lattice mismatched – their
> : atoms don't line up. The material properties of the mismatched
> : semiconductors allows for greater potential conversion of sunlight.
> : NREL is the U.S. Department of Energy's primary national laboratory
> : for renewable energy and energy efficiency research and
> : development. NREL is operated for DOE by Midwest Research Institute
> : and Battelle.
> Mark Reiff
>