National Research Council associate enables future mobile energy solutions for Air Force

  • Published
  • By Jeremy Gratsch
  • AFRL Materials and Manufacturing Directorate
WRIGHT PATTERSON AIR FORCE BASE --  The utilization of solar energy represents an important approach to helping meet the U.S. Air Force's future mobile energy needs. Although organic photovoltaic (OPV) devices offer ease of materials processing, low cost, and physical flexibility, they have power conversion efficiencies (PCEs) of only 5 to 10 percent. These efficiencies are below those of silicon devices (15 to 20 percent) due to OPV's exciton dissociation and charge carrier recombination problems.

OPV devices using single-walled carbon nanotubes (SWNTs) offer the potential to significantly increase PCEs beyond the current state-of-the-art through better exciton dissociation at the nanotube/conjugated polymer interface, and better charge transport due to the large aspect ratio of SWNTs and an effective semiconducting nanotube network.

However, severe problems associated with bulk nanotube mixtures have led to poor PCEs in all previous SWNT OPV devices. Recognizing this challenge, Air Force Research Laboratory (AFRL) scientist and National Research Council associate Dr. Ryan Kohlmeyer addressed the issue using single-chirality semiconducting SWNTs in OPV devices, which he believes will lead to a substantial improvement in PCEs.

Originally from Wisconsin, Dr. Kohlmeyer was hired as a contractor at AFRL's Materials and Manufacturing Directorate following his doctoral studies in organic chemistry at the University of Wisconsin Milwaukee. Although initially a chemist, Dr. Kohlmeyer considers himself more a materials scientist now and focuses his research and development activities on carbon-nano and smart materials.

"These materials have the potential to revolutionize clean energy applications, leading to increased flight and lifetimes for Air Force systems, increased battery life, better photovoltaics, and a decreased logistical burden related to transporting and carrying batteries," Dr. Kohlmeyer said. "A great deal of the Air Force's current focus in these areas is on increased power conversion efficiencies, flexible substrates, and increasing power per unit mass to create solutions targeted towards real world applications."

His collaborations with NRC Adviser Dr. Mike Durstock, as well as other AFRL colleagues, provides Kohlmeyer with the opportunity to see technologies move from bench-level testing to larger scale applications, which he admits is a source of great personal pride.

"There is a great opportunity to collaborate with incredibly talented and dedicated Air Force and industry researchers," Dr. Kohlmeyer added.

As an example, Dr. Kohlmeyer said he is currently working with a robotics expert on a growth chamber for carbon nanotubes.

"I believe that having access to incredible resources and people is where the solution to great scientific and technical challenges lies. AFRL has state-of-the-art facilities and the best and brightest minds the world has to offer," he said.