Building a Better Solar Panel
- By Joshua E. Brown
TV screens that roll up. Roofing tiles that double as solar panels. Sun-powered cell phone chargers woven into the fabric of backpacks. A new generation of organic semiconductors may allow these kinds of flexible electronics to be manufactured at low cost, says UVM physicist and materials scientist Madalina Furis.
But the basic science of how to get electrons to move quickly and easily in these organic materials remains murky.
To help, Furis and a team of UVM materials scientists have invented a new way to create what they are calling “an electron superhighway” in one of these materials—a low-cost blue dye called phthalocyanine—that promises to allow electrons to flow faster and farther in organic semiconductors. Their discovery, reported in the journal Nature Communications, will aid in the hunt for alternatives to traditional silicon-based electronics.
Many of these types of flexible electronic devices will rely on thin films of organic materials that catch sunlight and convert the light into electric current using excited states in the material called “excitons.” Roughly speaking, an exciton is a displaced electron bound together with the hole it left behind. Increasing the distance these excitons can diffuse—before they reach a juncture where they’re broken apart to produce electrical current—is essential to improving the efficiency of organic semiconductors.
Using a new imaging technique, the UVM team was able to observe nanoscale defects and boundaries in the crystal grains in the thin films of phthalocyanine—roadblocks in the electron highway. “We have discovered that we have hills that electrons have to go over and potholes that they need to avoid,” Furis explains.
To find these defects, the UVM team—with support from the National Science Foundation—built a large scanning laser microscope. The instrument combines a specialized form of linearly polarized light and photoluminescence to optically probe the molecular structure of the phthalocyanine crystals.
“Marrying these two techniques together is new; it’s never been reported anywhere,” says Lane Manning ’08 a doctoral student in Furis’ lab and co-author on the study.
Though the Nature Communications study focused on just one organic material, phthalocyanine, the new research provides a powerful way to explore many other types of organic materials, too—with particular promise for improved solar cells.
“One of today’s big challenges is how to make better photovoltaics and solar technologies,” says Furis, who directs UVM’s program in materials science, “and to do that we need a deeper understanding of exciton diffusion. That’s what this research is about.”