Awards Database

Scialog: Solar Energy Conversion - 2011

Lei Zhai

University of Central Florida

Investigating Charge Transport and Recombination in Bulk Heterojunction Organic Photovoltaics with Conjugated Polymer Columnar...

Solar researcher Lei Zhai’s goal: Generating electricity from ‘ink’

Lei Zhai, associate professor of chemistry and nanoscience at the University of Central Florida, is deeply involved in the race to produce cheap, effective devices to generate electricity directly from sunlight, a process known as “photovoltaics.” He recently received a $100,000 grant from Research Corporation for Science Advancement (RCSA) to further his work. RCSA, America’s second-oldest foundation, supports the innovative investigations of early-career scientists. Zhai said he would like to see his research ultimately result in an electricity-generating “ink” that could easily and rapidly be sprayed on a substrate to create solar panels. He hopes to achieve this by radically improving efficiencies in what solar researchers call bulk heterojunctions. A bulk heterojunction is simply a mixture of two dissimilar semiconductors with enormous interfacial area between these two materials. A semiconductor is a material with a crystalline atomic structure—that is, its atoms are arranged in a three-dimensional lattice. When sunlight strikes a solar panel, the atoms in one of the semiconductors tend to lose their outer electrons. That’s because these outer, or “valence,” electrons are good at absorbing photons, the smallest particle, or quantum, of light. The act of absorbing a photon excites the valence electron, and it tends to go wandering off from the atom where it had been parked, through a convenient on-ramp to what is called the “conduction band.” Think of it as a special freeway lane for the excited electrons that travel only at a very specific range of speeds (energy levels). These electrons move to the other semiconductor at the interfaces which can be considered as highway cross-sections, and continue travel to an electrode. In a solar panel this process happens endlessly and at a rate of hundreds of millions of times per second – at least when the sun is shining. The lattice structure of the semiconductor allows for the collection and orderly flow of these excited electrons, which is another way of saying an electrical current is generated. Zhai’s work involves adjusting relatively inexpensive carbon-based semiconductors to get them to produce electricity. To achieve his “dream outcome” of a sprayable, power-generating liquid, he is combining and then testing many variations of fullerenes and polymers: A fullerene is defined as any molecule composed entirely of carbon atoms and that comes in the form of a hollow sphere, ellipsoid or tube. (Spherical fullerenes are also called buckyballs; cylindrical fullerenes are called carbon nanotubes.) The fullerene was named for futurist and visionary Buckminster Fuller (1895-1983), inventor of the geodesic dome. A polymer, on the other hand, seems somehow much less attractive than the elegant fullerene. It is any molecule composed of long, repeating chains of smaller molecules or atoms. In this case Zhai is working with polymers most of us would generally consider to be plastics, more or less the stuff of ordinary grocery bags. Tweaking the many variables in this large class of molecules and combining them with fullerenes in the hope of generating dramatically increased amounts of electricity is certainly a long shot at best. And that’s precisely why RCSA is funding Zhai’s project. The foundation’s president and CEO, James M. Gentile, noted that RCSA founder Frederic Cottrell once wrote: “Bet on the youngsters. They are long shots, but some of them pay off.” Over the past 100 years, Gentile pointed out, that philosophy has led RCSA to support fundamental science leading directly to space travel, lasers, MRI machines for peering into the living human body, so-called “wonder” drugs such as corticosteroids, nuclear medicine and atomic science, among many other modern achievements. Zhai is funded through RCSA’s Scialog® program, which Gentile said is specifically designed to support “high-risk/potentially high-reward research on challenges of great global significance.” Developing clean, renewable sources of energy is one such challenge, he added. Scialog is formed from the words “science” and “dialog.” The program requires Scialog fellows such as Zhai to attend annual meetings where they are encouraged to discuss their most innovative and “far-out” ideas, Gentile said. “Scialog is an experiment in accelerating the pace of breakthrough scientific discoveries,” Gentile said. “Creative researchers like Lei Zhai represent the world’s best hope for a brighter tomorrow. RCSA is proud to support them.”

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