Fully monolithically integrated flexible solar module (consisting of 6 cells) based on cadmium telluride (CdTe): Empa researchers recently achieved a new world record in energy conversion efficiency of 13.8 percent with this type of solar cell. |
DuPont
Kapton colorless polyimide film, a new material currently in
development for use as a flexible superstrate for cadmium telluride
(CdTe) thin film photovoltaic (PV) modules, has faciliated a new world
record for energy conversion efficiency. A team at Empa, the Swiss
Federal Laboratories for Materials Science and Technology, has
demonstrated a conversion efficiency of 13.8% using the new colorless
film, leapfrogging their previous record of 12.6% and nearing that of
glass.
Because
Kapton film is over 100 times thinner and 200 times lighter than glass
typically used for PV, there are inherent advantages in transitioning to
flexible, film-based vs. rigid glass CdTe systems. High-speed and
low-cost roll-to-roll deposition technologies can be applied for
high-throughput manufacturing of flexible solar cells on polymer film as
substrates. The new polyimide film potentially enables significantly
thinner and lighter-weight flexible modules that are easier to handle
and less expensive to install, making them ideal for applications
including building-integrated photovoltaics.
“Rather
than transporting heavy, fragile glass modules on large trucks and
lifting them by crane onto rooftop PV installations, one could imagine
lightweight, flexible film-based modules that could simply be rolled up
for transport, and easily carried up stairs,” said Robert G. Schmidt,
new business development manager, Photovoltaics – DuPont Circuit &
Packaging Materials.
“With
record-setting efficiency established through Empa, we’re confident
this flexible, lightweight and durable material has the potential to
revolutionize the industry by enabling flexible design and lowering
balance of system costs.”
Increase in efficiency – toward achieving grid parity
Empa’s
Laboratory for Thin Films and Photovoltaics is developing
high-efficiency thin film solar cells with emphasis on novel concepts
for enhancing their performance, simplifying the fabrication processes,
and advancing device structures for next generation of more efficient
and low-cost devices. They have been doing groundbreaking work in
developing and optimizing a low deposition temperature process (below
450 degrees Celsius) for high-efficiency CdTe solar cells on glass
(reaching 15.6% efficiency) and polymer film (reaching 12.6% efficiency,
the highest value before the recent improvement to 13.8%). Only a few
weeks ago Tiwari’s team also set a new world record in energy efficiency
(of 18.7%) for another type of flexible solar cells based on copper
indium gallium (di)selenide (also known as CIGS).
“Finding
a film that could both be transparent and withstand high processing
temperatures was a challenge initially, but the new Kapton colorless
polyimide film had both the tolerance for high temperatures needed, and
higher light transmittance due to its transparency that allowed it to
exceed our previous world record in conversion efficiency of flexible
CdTe solar cell,” said Ayodhya N. Tiwari, head of the laboratory. “As we
continue to raise the standards for PV efficiency, materials make a
distinct difference in the progress we make toward achieving grid
parity. Of course, further development is needed for addressing cost and
stability issues.”
Tiwari
plans to present a technical paper on the full findings at the 26th
European Photovoltaic Solar Energy Conference and Exhibition in Hamburg,
Germany, being held Sept. 5–9, 2011.
Three
new Kapton PV9100 series films were introduced for the thin film PV
market in 2010, including offerings for amorphous silicon (a-Si) modules
and copper indium gallium selenide (CIGS) photovoltaic applications.
