A special
invisibility cloak (right) guides sunlight past the contacts for current
removal
to the active
surface area of the solar cell. (Graphics: Martin Schumann, KIT)
(September 30, 2015) Invisibility
Cloak Principle: Material Hides Contact Fingers that Extract Current from Solar
Cells and Cover the Active Surface – Measurements Confirm Cloaking Effect
Success of the energy turnaround will depend decisively on
the extended use of renewable energy sources. However, their efficiency partly
is much smaller than that of conventional energy sources. The efficiency of
commercially available photovoltaic cells, for instance, is about 20%.
Scientists of Karlsruhe Institute of Technology (KIT) have now published an
unconventional approach to increasing the efficiency of the panels. Optical
invisibility cloaks guide sunlight around objects that cast a shadow on the
solar panel, such as contacts for current extraction. DOI:
10.1364/OPTICA.2.000850.
Energy efficiency of solar panels has to be improved
significantly not only for the energy turnaround, but also for enhancing
economic efficiency. Modules that are presently mounted on roofs convert just
one fifth of the light into electricity, which means that about 80% of the
solar energy are lost. The reasons of these high losses are manifold. Up to one
tenth of the surface area of solar cells, for instance, is covered by so-called
contact fingers that extract the current generated. At the locations of these
contact fingers, light cannot reach the active area of the solar cell and
efficiency of the cell decreases.