chemical engineers have developed a way to concentrate
solar energy 100 times more than a traditional photovoltaic
cell through the use of carbon nanotubes.
Han, postdoctoral associate and lead author; Geraldine Paulus,
graduate student and lead author; and Michael Strano, leader of the
research team have devised a way to use carbon nanotubes (hollow
tubes of carbon atoms) to form antennas that capture and focus light
energy, resulting in more powerful and smaller solar arrays.
of having your whole roof be a photovoltaic cell, you could have
little spots that were tiny photovoltaic cells, with antenna's that
would drive photons into them," said Strano.
panels convert photons into an electric current to generate
electricity, but with the use of the nanotube antenna, the number of
photons being captured increases and light is transformed into energy
that can be funneled into the solar cell.
new antenna's are called "solar funnels," and can be used
in various other applications such as telescopes or
night-vision goggles, where light needs to be concentrated. They
contain a fibrous rope that is 10 micrometers long and four
micrometers thick, and consist of 30 million carbon nanotubes. The
fiber is made up of two layers of nanotubes with different bandgaps,
which is the difference in energy levels between an electron and the
hole it leaves behind. When photons strike a surface, this excites
the electron to a higher degree depending on the material, and
interactions between the electron and the hole it leaves behind is an
outer layer of the nanotubes have a higher bandgap while the inner
layer has a lower bandgap, and the excitons flow from the higher to
lower energy. When light strikes the material, the excitons become
more concentrated, flowing to the center of the fiber.
makes this study such a significant advancement is that it's the
first to construct nanotube fibers where the properties of different
layers can be controlled. Costs of carbon nanotubes originally
prohibited this kind of experimentation, but prices have fallen and
made the nanotubes more accessible.
next step is to build a photovoltaic device using the antenna, where
the antenna would concentrate photons before they are converted into
an electrical current by the photovoltaic cell. The antenna would be
constructed around a core of semiconducting material and the system
electricity by separating the electron from the hole and
collecting electrons at one electrode on the inner semiconductor and
collecting holes at the other electrode touching the nanotubes.
research team is also looking to increase the number of excitons per
photon, and to decrease the energy lost as excitons "flow
through the fiber."
study was published in Nature
quote: ...and the hole it leaves behind is an exciton.