dispersion. These structures can control the rate of spontaneous emission and absorption via
interaction of the local density of optical modes with dipole absorptions and emitters. For solar
absorbers that employ heterogeneous assemblies of nanostructures or optical wavelength-scale
structures, coupling of incident radiation to the solar absorber can be enhanced by use of periodic
dielectric or metallodielectric structures that modify or control the density of optical modes
available for light absorption and light emission.
POTENTIAL IMPACT
The majority of existing terrestrial photovoltaic devices (>99%) are based on single-junction
photovoltaic concepts which have an efficiency limit of ~32%. A new generation of photovoltaic
devices can allow both dramatic improvements in efficiency and lower cost. However, the
realization of such devices faces multiple scientific challenges. Solutions to these scientific
challenges will not only allow solar energy to tunnel through the cost/performance barriers faced
by existing photovoltaic devices, but will also contribute to the issues faced by many of the solar
conversion technologies, such as organic, photochemical, thermophotovoltaic, and biologically
inspired energy conversion systems. The potential impact of being able to put any material on
any other material while still maintaining excellent performance will revolutionize the
photovoltaics industry by allowing the integration of multiple materials into multijunction cells,
enabling achievement of 50% efficiency and associated growth of a multijunction concentrator
industry. Furthermore, this capability will allow high-performance, thin silicon cells to overcome
the current shortage of silicon feedstock.
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