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An international team of scientists that includes NIU researchers has mapped out a pioneering route to improve the performance of hybrid perovskite solar cells.
This type of cell is so named because it uses a crystal structure similar to that found in the mineral known as perovskite. When compared to traditional solar cells made of silicon, perovskite cells are greener and more cost efficient to produce. They have been the subject of intense interest among materials scientists, who have been successfully working in recent years to increase their efficiency for converting sunlight to electricity.
The new research represents another stride toward improving the perovskites and making them commercially viable.
“In short, we have found a clean and effective way to push perovskite photovoltaic materials toward their best performance,” says NIU chemistry and biochemistry professor Tao Xu, a member of the research team.
The team’s study was published recently in the prestigious journal, Proceedings of the National Academy of Sciences. Xu co-designed the project, and co-wrote the PNAS article with first author Lingping Kong of the Center for High Pressure Science and Technology Advanced Research in Shanghai.
“The development of solar cells demands aggressive research into potential inventions of new and better photovoltaic materials,” says Xu, who received a National Science Foundation early career development grant in 2012. “No materials are perfect, and many formidable challenges need to be tackled before perovskites can be commercialized.”
In solar cells, active photovoltaic materials convert light to electrical charges, called charge carriers. The power of the solar cells depends on the total number of charge carriers generated and on the average energy in each charge carrier, with more energy resulting in a longer lifetime to be collected before recombination.
The sun emits a mixture of lights with different colors ranging from blue to red. In general, blue light creates more energetic carriers, but if the cells are designed to capture only blue light, the carrier numbers are less abundant.
One of the major challenges with perovskite solar cells is to improve the material’s absorption of red light while retaining the long lifetime of the charge carriers in perovskite materials. Xu and colleagues overcame the challenge by tuning the perovskite structures via hydrostatic pressure. Using this technique, their samples of organic–inorganic hybrid lead trihalide perovskites absorbed redder light while significantly prolonging the charge-carrier lifetimes.
“We discovered a mechanism for tuning the structural parameters of the material under mild pressures and achieved simultaneous enhancement in light absorption and carrier lifetime prolongation, without any adverse chemical or thermal effects,” Xu said, adding that carrier lifetimes increased by 70 percent to 100 percent. “We believe this work will create a roadmap for further improvement of hybrid perovskite materials.”
Xu’s Ph.D. student at NIU, Jue Gong, also was a member of the research team, along with scientists from the Carnegie Institute of Washington, Argonne National Laboratory, the National Renewable Energy Laboratory and other institutions.
Contact: Tom Parisi, NIU Newsroom