High efficiency Solar cells
A BRAIN CHILD OF
UC BERKELEY / UNIVERSITY OF ILLINOIS
Terms to be acquainted with
A quantum dot is a semiconductor
nanostructure that confines the motion of
conduction band electrons, valence band
holes, or excitons (bound pairs of
conduction band electrons and valence
band holes) in all three spatial directions.
The lights in this room, the TV at home and the
mobile screens we use everyday and LEDs work
on the concept of luminophores.
It’s basically a functional group that causes
luminescence or illumination when exposed to a
certain electrical or optical stimulus.
The use of luminophore is essential in increasing
efficiency. The technology which uses this in Solar
cells is called Luminescent Solar Collectors. (LSC)
A luminescent solar concentrator (LSC) is a
device that uses a thin sheet of material to
trap solar radiation over a large area, before
directing the energy (through luminescent
emission) to cells mounted on the thin
edges of the material layer.
Because of the phenomenon called Stokes
shift, the blue high energy light is re-emitted
as red light with more than 80% conversion
efficiency and minimum losses.
Use of Luminophores in High
efficiency Solar Cells
Current solar cell technology -> High area ->
LSC -> Same area -> Re-emitted radiation
concentration-> Greater collection
Hence LSC uses the same area to a greater
Coupling that with concentration on a small PV
cell increases the efficiency of the solar cell
By combining designer quantum dot light-emitters with
spectrally matched photonic mirrors they created solar cells
that collect blue photons at 30 times the concentration of
conventional solar cells. With a sufficient concentration
factor, only small amounts of expensive III−V photovoltaic
materials are needed to collect light from an inexpensive
They replaced the molecular dyes in previous LSC systems
with core/shell nanoparticles composed of cadmium selenide
(CdSe) cores and cadmium sulfide (CdS) shells that
increase the Stokes shift while reducing photon re-
The CdSe/CdS nanoparticles enabled them to decouple
absorption from emission energy and volume, which in turn
allowed to balance absorption and scattering to obtain the
optimum nanoparticle. The use of photonic mirrors that are
carefully matched to the narrow bandwidth of the quantum
dot luminophores achieved waveguide efficiency exceeding
Added advantage: Transparency!
The use of a Luminescent Solar concentrator allows
the use of organic dyes to trap light within a given
This way the light can be directed by Total Internal
reflection onto a Solar cell.
So basically the light falling on a flat surface can be
directed at its edges. Imagine your windows collecting
the light and sending it to the solar cells at the edges!
And the use of organic dyes can cause a transparent
waveguide to form.