Assistant Professor of Chemisty
Yiying Wu | Ohio State University, Columbus
Dyes, Daylight and Doing Good
Years ago in a small city in China, a curious child fooling around with chemistry dipped electric wires into salty water. Oops.
"It generated bubbles," says Yiying Wu, now on the Ohio State chemistry faculty. "And there was a strange smell." As the ions of salt yielded to his attack, the room smelled of chlorine gas, just as he predicted.
Of course, he blew a fuse. Happily, no one else in his part of Tunxi, an ancient city in Anhui Province, lost power, and to this day, Wu says, his parents don't know what he did. But he was on a search for new uses of molecules, in particular dye molecules, to capture solar energy.
Today he studies how dyes - like the red in a tomato or the dyes in green tea or black tea - can absorb photons and help build better solar cells. "That's the cool thing about technology," Wu says. "We can show kids things in the kitchen that can make a solar cell."
A kitchen experiment, he says, could make use of titanium dioxide, say, from sun screen. The oven could burn away organic parts, leaving a paste to coat a piece of special glass that is transparent and conductive. Immerse the glass in the dye from juice or tea, add a counter electrode and sunlight and you have the idea - a dye-sensitized solar cell.
Wu received a B.S. in chemical physics from the University of Science and Technology of China, also in Anhui. A Ph.D. in chemistry from UC Berkeley came next. After postdoctoral research at UC Santa Barbara, he joined Ohio State in 2005.
His work may one day aid a global response to the energy challenge. "We have a clear idea of what's up in the solar cell," he says, "and how to design new materials to improve their efficiency."
Education Component
At Ohio State, the education component of his Cottrell award will consist of creating freshman seminar class on alternative energy technologies, as well as helping run a science education program aimed at collaboration between scientists and elementary school teachers. The program will develop experiments to demonstrate science in classes from kindergarten up.
Meanwhile, Wu's research will include creating new electrode materials and architectures for solar cells that make use of dyes. Dye molecules attach to a support material in the cell - like titanium dioxide - and turn on the electrons from ground state to an electrically excited state after capturing energy from sunlight.
"It's similar to photosynthesis in nature," he explains. Dye molecules act like pigment chlorophyll in plants. The difference is that photosynthesis converts solar energy into chemical energy, while a dye-sensitized solar cell converts it into electricity.
His research, he says, could improve the way in which electrons migrate to a solar cell's electrode and on to do useful work - lighting streets or playing music, or to be stored.
"The energy from the sun in one hour could provide enough energy for all humans to use in one year," he says. "In principle, there's no need to worry about the energy challenge. "
What's needed are cheap solar cells to run at high efficiency. That could make a huge impact on the world's energy needs, he says. In five to 10 years, he says, a vital element could be dye-sensitized solar cells. "I am very optimistic about that," he says.
