Triple Layer - Flexible and Rigid Modules
Unisolar has developed a range of
modules which are up to 30% more efficient even in cloudy weather.
These thin film, triple junction, photovoltaic modules are the
product of technological breakthroughs, which combined with improved
manufacturing processes means an efficient panel at a cost effective
price.
Flexible & rigid Amorphous photovoltaic
(pv) material is deposited on a substrate of stainless steel in
separate layers. These layers are called multi-junctions.
All ends of the spectrum are utilized
to produce electricity because three of these layers are each
specifically tailored to a different portion (area) of the spectrum.
The wide band junction, absorbs higher energy photons at the red
end of the spectrum, sunlight bright enough to cast a shadow.
Narrower bands form junctions designed to absorb a portion of
the lower light frequencies nearer the green and blue end of the
spectrum which is prevalent in cloudy weather.
Shadow tolerant
These modules are not only low light
sensitive they are also shadow tolerant, with a large number of
integrated bypass diodes enabling it to operate even when partially
shadowed. The performance of conventional modules comes down to
zero even if one cell is shaded.
Technology
All United Solar products are based
on a sophisticated multi-layer amorphous silicon thin-film solar
cell developed originally by Energy Conversion Devices, Inc. This
spectrum-splitting cell, shown schematically below, is constructed
of three separate p-i-n type, amorphous semiconductor solar sub-cells,
each with a different spectral response characteristic. In this
way, the cell can convert the different visible and near infrared
wavelengths of sunlight with optimal efficiency. The United Solar
spectrum-splitting multijunction design now holds all the world's
records for amorphous silicon solar cell efficiency, including
the highest stable efficiency measured by the National Renewable
Energy Laboratory (NREL) for a small-area amorphous silicon solar
cell -- 13 percent.
