Green Collar Careers - Thin Film
The next generation of solar PV cells may add several new
technologies with higher efficiencies and/or lower costs. Over
the last decade there has been a tremendous rise with development of
Thin Film Photo Voltaic (TFPV) technology. TFPV offers several
solutions to the limitations of silicon PV cells including lower cost
and higher efficiencies. Production methods are very different from
silicon PV cells and many of the up & coming producers are still
refining manufacturing processes for mass production.
some of the band gap restrictions TPFV produces more power under less
optimal "filtered" sunlight conditions including cloudy days as well
as morning & evening light. Some systems are being installed
with solar tracking as the cost is now offset.
There are a few
different key material technologies used in TFPV design, each offering
different advantages. Three of the leading technologies are:
- Cadmium Telluride (CdTe)
- Copper indium gallium selenide (CIGS)
- Thin-film silicon (TF-Si)
CdTe uses a nearly transparent film of Cadmium and Tellurium
on sheets of glass eliminating the need for more costly pure silicon.
Under optimal "high noon" conditions these cells are slightly less
efficient then silicon, however over the course of a day and in
particular under cloudy conditions, these cells produce more power
then silicon PV's.
They are not without some disadvantages. Cadmium and
Tellurium are both toxic materials to handle through manufacturing and
disposal. Once in the finished panel they are considered quite
safe. Although the raw material costs are much lower then
silicon, they manufacturing process is somewhat more expensive,
typically a vapor deposition method. As production is ramping
economies of scale are beginning to show significant cost reductions
and the current cost comparison to silicon per actual production watt
is about 70%.
Due to the limited production CdTe is only available
to commercial operations that produce over 50 kW per installation,
and even then there is an 18-24 month waiting list.
uses less hazardous and generally more available materials then CdTe
however has a more complex manufacturing process to control.
Recent advances in electroplating are likely to reduce the cost over
the next five years. CIGS has demonstrated higher efficiency
capability then most commercially available silicon PV reaching
close to 20%. Several key advantages with exploiting a varied
range of band gap efficiencies are still in development with some
very optimistic theories on substantially higher efficiencies yet
A major advantage is this technology can be applied to
flexible substrates. There are a few manufacturers producing
solar films that can be applied to windows that both reduce the
sunlight and generate electricity. Flexible substrates open up
many new possibilities for architectural solutions.
are primarily a shorter expected operating life. Materials
used have an affinity to absorb moisture that quickly corrodes the
films so the layers must remain sealed to the environment.
TF-Si is still silicon based however rather then binning with an
expensive pure silicon cast ingot, they rely on thin films of
silicon generally applied with chemical deposition or sputtering
techniques. These have a lower efficiency then traditional
silicon PV's however also have a lower cost per actual production
watt. There are developments that have produced flexible
translucent substrates providing attractive prospects for building
integration similar to the CIGS thin films for windows. There
are few companies that are investing much into developing this
technology so it may not become a major player in the next
generation of solar PV cells.