WASHINGTON — The U.S. Department of Energy (DOE) reports that
several recent advances could bring new solar cell technologies that convert a
large fraction of sunlight into electricity — if the technologies can be
commercialized. These technologies relate to everything from the surface of
solar cells to their very heart.
Researchers at Rensselaer Polytechnic Institute (RPI) announced
that they have developed an antireflective coating that captures the entire
spectrum of sunlight from any angle. The researchers stacked seven layers of
antireflective coating, each about 100 billionths of a meter thick, or 100
nanometers. Each layer is composed of nanoscale rods, all positioned at an
oblique angle. The arrangement allows each layer to enhance the antireflective
qualities of the layer below it, resulting in a highly efficient capture of
sunlight. The work was funded by the DOE Office of Basic Energy Sciences.
Researchers from the Massachusetts Institute of Technology (MIT)
took a similar approach to boosting solar cell efficiency, but focused their
efforts on the back of ultrathin silicon solar cells. The team applied an
antireflection coating to the front of the cell and covered the back with
multiple layers of reflective coatings and a diffraction grating, trapping
light within the cell and boosting its efficiency by up to 50 percent. Going
back to the front of the cell, Sunovia Energy Technologies Inc. and EPIR
Technologies Inc. have developed a glass ceramic material with nanoscale
crystalline particles embedded in it that is transparent to visible light but
converts ultraviolet light into visible light as it passes through. The material
could be used as a cover on rigid solar modules, increasing their conversion
efficiencies.
Turning to the heart of the solar cell, researchers at Ohio State
University (OSU) have devised a potential solar cell material that can capture
the entire visible portion of sunlight. The material, an electrically
conductive plastic combined with metals, such as molybdenum and titanium, is
still a long way from a functional solar cell, but it has promising properties,
including the ability to generate electrons that remained in an excited energy
state for a relatively long period of time.
Publication date: 12/22/2008
