Columbia University professor developing new kind of solar cell

When most people look at a skyscraper in New York City, they see a tall building with many windows. Xiaoyang Zhu sees a potential army of solar power providers.

Zhu — a professor of chemistry at Columbia University and a native of Suzhou in Jiangsu province — and a team of researchers are developing a new class of ingredients for solar-cell production.

The name for those ingredients is a tongue twister: Hybrid Organic Inorganic Perovskites, or HOIPs. But their end-goal is simple: easily achieve largescale and low-cost production of solar cells, as well as greater efficiency.

Zhu and the team are using funding from the US Department of Energy and the National Science Foundation to develop HOIPs.

“When you look at a skyscraper in New York City you see hundreds of windows that are tinted to keep out the sunlight,” Zhu said on Tuesday. “Imagine that we work with the glass manufacturers to replace the tint on those windows and turn them into a solar panel. Suddenly we don’t need to run electricity to cool down all of those rooms.”

Solar cells turn sunlight into electricity and most are on panels that are made from silicon layers. The process that is used to make the silicon layers is expensive and time consuming. Silicon cells are very fragile as even a minuscule amount of dust or dirt can seriously reduce the cells’ effectiveness.

“These (HOIPs) are a material that you pour out of a solution at room temperature which means you can easily achieve large-scale and low-cost production,” Zhu said.

The other major advantage for HOIPs over silicon-produced solar cells is increased efficiency. Zhu said that it took six years for HOIPs to reach a 22 percent level of power conversion efficiency. But it took from 50 to 60 years for silicon cells to reach the same level, he added.

There is a drawback to HOIPs, said Zhu. They contain lead and are also water soluble. That means the solar cells may dissolve and leak lead. “We haven’t found an alternative to lead yet but it is only a matter of time,” said Zhu.

The team at Columbia has been investigating HOIPs since 2014. In 2009, scientists in Japan demonstrated it was possible to build solar cells out of HOIPs, and that these cells could harvest energy from sunlight even when they had defects.

Zhu said the use of solargenerated power is growing quickly. He pointed to Germany, “which is a country that is not well known for sunshine. On average, about 37 percent of Germany’s electricity production is from renewables”.

Zhu believes that HOIPs can help shift electricity production to renewables like solar in the US and China.

“Solar is a fast-growing sector of the economy and there is no reason why we can’t make it an even larger part,” he said.

The team is led by Zhu and also includes Haiming Zhu and Kiyoshi Miyata, two postdoctoral fellows at Columbia. Other members include graduate students Jue Wang, Prakriti Joshi, Kristopher Williams and postdoc Daniel Niesner, all of Columbia; Yongping Fu and Song Jin, collaborators from the University of Wisconsin Madison.

Their results have been reported in the journal Science.

professor of chemistry, Columbia University

Xiaoyang Zhu,