A variety of research companies and universities are working to advance spray-on organic photovoltaics (OPV) with the aim of coating glass, curved plastics and other materials at commercial volume in the near future. A key to several of these developments is that a manufacturing process likely will evolve using roll-to-roll or sheet-to-sheet technology in conjunction with jet spray.

Part of the funding for these advances is coming from the U.S. Department of Energy’s (DOE) SunShot program, aimed at improving solar and driving down the cost. The federal government estimates the United States can save $40 billion per year by reducing energy use in commercial buildings by 20 percent by 2020.

In early November, Scottsdale, AZ-based NanoFlex Power Corp. won a $1.35 million cooperative award from SunShot, under the “Next Generation Photovoltaics 3” program; it was the only project awarded for OPV research and development in this round of financing, NanoFlex announced. The company is conducting Gallium Arsenide (GaAs) solar cells research with the University of Southern California and the University of Michigan, which are leaders in the field of organic electronics, including organic light emitting diodes, or OLEDs, and OPV.

Under the award, the University of Michigan “will advance the practical viability of OPV by demonstrating reliable, large area and high-efficiency organic multi-junction cells based on small molecule materials systems.” The project’s goals focus on “improving the conversion efficiency of OPV cells to more than 18 percent, increasing cell lifetimes to over 20 years, and demonstrating ultra-rapid fabrication processes through proprietary vapor phase deposition and roll-to-roll application of package encapsulation.”
Early OPV research yielded light converting efficiency of only six or seven percent, but those levels have been nearly doubled, according to several different project announcements this year. Typically, solar glass coatings trap both external solar light and internally-generated light.

And last year, New Energy Technologies, based in Columbia, MD, moved into Phase 2 of its Cooperative Research and Development Agreement (CRADA) with DOE’s National Renewable Energy Laboratory (NREL) to advance the development of its SolarWindow technology, capable of generating electricity on glass. Included in this stage of work is the commercialization of roll-to-roll or sheet-to-sheet manufacturing techniques.

In March, NREL tested a SolarWindow version that was about three square feet and was transparent. “The window performed 50 times better than previous versions and set the record as the most efficient organic photovoltaic cell (OPV) ever tested by the NREL,” Solar Technologies indicated. NREL operates the Device Performance Measurement Laboratory for such materials testing. New Energy Technologies points out that its process“ does not require expensive high-temperature or high-vacuum production methods, but rather, can be sprayed on to glass at room temperature.”

“Accomplishing these goals allows us to now advance towards larger area, commercial scale windows while maintaining uniform, neutral colors and scalable power,” said John Conklin, the president and CEO of New Energy Technologies.
Another team at work on PV paint is at the University of Sheffield, involving sprayed perovskite, a calcium titanium oxide mineral that absorbs light nearly as well as silicon. This project has achieved a reported 11 percent efficiency thus far.