Kanatzidis, the Charles E. and Emma H. Morrison Professor of Chemistry in the Weinberg College of Arts and Sciences, and Chang, a professor of materials science and engineering at the McCormick School of Engineering and Applied Science, are the two senior authors of the paper.
"This is the first demonstration of an all solid-state dye-sensitized solar cell system that promises to exceed the performance of the Grtzel cell," Chang said. "Our work opens up the possibility of these materials becoming state of the art with much higher efficiencies than we've seen so far."
The Northwestern cell exhibits the highest conversion efficiency (approximately 10.2 percent) so far reported for a solid-state solar cell equipped with a dye sensitizer. This value is close to the highest reported performance for a Grtzel cell, approximately 11 to 12 percent. (Conventional solar cells made from highly purified silicon can convert roughly 20 percent of incoming sunlight.)
Unlike the Grtzel cell, the new solar cell uses both n-type and p-type semiconductors and a monolayer dye molecule serving as the junction between the two. Each nearly spherical nanoparticle, made of titanium dioxide, is an n-type semiconductor. Kanatzidis' CsSnI3 thin-film material is a new kind of soluble p-type semiconductor.
"Our inexpensive solar cell uses nanotechnology to the hilt," Chang said. "We have millions and millions of nanoparticles, which gives us a huge effective surface area, and we coat all the particles with light-absorbing dye."
A single solar cell measures half a centimeter by half a centimeter and about 10 microns thick. The dye-coated nanoparticles are packed in, and Kanatzidis' new material, which starts as a liquid, is poured in, flowing around the nanoparticles. Much like paint, the solvent evaporates, and a solid mass results. T
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