April 18, 2012
Lou and co-lead investigator Hong Lin, a professor of materials science and engineering at Tsinghua, detailed their work in the online, open-access Nature journal Scientific Reports this week.
DSCs are easier to manufacture than silicon-based solid-state photovoltaic cells but not as efficient, said Lou, a professor of mechanical engineering and materials science. “DSCs are sensitized with dyes, ideally organic dyes like the juices from berries – which some students have actually used in demonstrations.”
Dyes absorb photons from sunlight and generate a charge in the form of electrons, which are captured first by a semiconducting titanium oxide layer deposited on a current collector before flowing back to the counter electrode through another current collector. Progress has been made in the manufacture of DSCs that incorporate an iodine-based electrolyte, but iodine tends to corrode metallic current collectors, which “poses a challenge for its long-term reliability,” Lou said.
Iodine electrolyte also has the unfortunate tendency to absorb light in the visible wavelengths, “which means fewer photons could be utilized,” Lou said.
So Tsinghua researchers decided to try a noncorrosive, sulfide-based electrolyte that absorbs little visible light and works well with the single-walled carbon nanotube carpets created in the Rice lab of Robert Hauge, a co-author of the paper and a distinguished faculty fellow in chemistry at Rice’s Richard E. Smalley Institute for Nanoscale Science and Technology .
“These are very versatile materials,” Lou said. “Single-walled carbon nanotubes have been around at Rice for a very long time, and people have found many different ways to use them. This is another way that turns out to be very well-matched to a sulfide-based electrolyte in DSC technology.”
Both Rice and Tsinghua built working solar cells, with similar results. They were able to achieve a power conversion efficiency of 5.25 percent – lower than the DSC record of 11 percent with iodine electrolytes and a platinum electrode, but significantly higher than a control that combined the new electrolyte with a traditional platinum counter electrode. Resistance between the new electrolyte and counter electrode is “the lowest we’ve ever seen,” Lou said.
Pei Dong, a graduate student in Lou’s lab, and Feng Hao, a graduate student at Tsinghua, are lead authors of the paper. Co-authors include Rice graduate students Jing Zhang and Philip Loya, Yongchang Zhang of Tsinghua and Professor Jianbao Li of Hainan University, China.
The project was supported by the National High Technology Research and Development Program of China, the Welch Foundation and the Faculty Initiative Fund at Rice.
Source: Rice University
- Nature journal Scientific Reports this week ("High Electrocatalytic Activity of Vertically Aligned Single-Walled Carbon Nanotubes towards Sulfide Redox Shuttles").