Efficiency Record Set for Flexible CdTe Solar Cell

An efficiency record has been set for flexible CdTe solar cells, thanks to a new polymide film developed by DuPont in collaboration with the Swiss Federal Laboratories for Materials Science and Technology (EMPA).

Kapton polymide film is more than 100 times thinner and 200 times lighter than glass typically used for photovoltaics (PV), which makes the new substrate easier to handle and less expensive to install. What is more, 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.

"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 of 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 – achieving grid parity

EMPA's Laboratory for Thin Films and Photovoltaics is developing high-efficiency thin-film solar cells with an 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 ºC) for high-efficiency CdTe solar cells on glass (reaching 15.6 percent efficiency) and polymer film (reaching 12.6 percent efficiency, the highest value before the recent improvement to 13.8 percent). Only a few weeks ago, the lab team also set a world record in energy efficiency (18.7 percent) for another type of flexible solar cell based on copper indium gallium (di)selenide (also known as CIGS). (See: Flexible Solar Cells Set Efficiency Record)

"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.

Tiwari plans to present a technical paper on the full findings at the 26th European Photovoltaic Solar Energy Conference and Exhibition in Hamburg, Germany, on Sept. 5, 2011.

For more information, visit: www.empa.ch