DuPont Kapton Colorless Polyimide Film Enables World Record for Flexible CdTe PV Efficiency

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 enabled a new world record for solar cell conversion efficiency.

Empa, a leading research institute for material sciences and technology development, based in Dübendorf, Switzerland, has demonstrated a conversion efficiency of 13.8 percent using the new DuPont Kapton colorless film, leapfrogging their previous world record of 12.6 percent and nearing that of glass.

Because Kapton film is more than 100 times thinner and 200 times lighter than the weight of 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. This new Kapton 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 (BIPV).

“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 already 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.”

“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 Prof. Dr. Ayodhya N. Tiwari, head of the laboratory – Empa. “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.”

Empa plans to present a technical paper on the full findings of its study 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.