Research highlights: Perovskites
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RESEARCH HIGHLIGHTS :
Perovskites
By Prachi Patel Feature Editor: Pabitra K. Nayak
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esearch on perovskites has progressed rapidly since the first solar cells with less than 4% efficiency were reported in 2009. MRS Bulletin presents the impact of a selection of recent advances in this burgeoning field. Perovskites are mostly being studied for solar cells. Now chemists at
Columbia University and the University of Wisconsin–Madison have made tiny lasers from single-crystal nanowires of methylammonium lead halide perovskites. Compared to nanowires made from conventional semiconductors such as zinc oxide and gallium arsenide, perovskite nanowires can be
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make solar cells that were 17.9% efficient. The researchers have now broken their own efficiency record by using the same materials but a new manufacturing method, which they reported in the June issue of Science (DOI: 10.1126/ science.aaa9272). Formamidinium-based perovskites absorb a larger portion of the solar spectrum compared to methylammonium-based compounds, leading to
grown easily at room temperature, says Columbia University chemistry professor Xiaoyang Zhu. As reported in the June issue of Nature Materials (DOI: 10.1038/NMAT4271), the researchers make the single-crystal nanowires by depositing a solid thin film of lead acetate on a glass surface and then adding a high concentration methylammonium iodide solution. This led to the a b growth of rectangular nanocrystals of perovskite that were defect-free and had the reflective parallel facets needed to make a laser. Measurements showed that the perovskite nanowire lasers are 100% efficient at converting absorbed photons to laser light, at least one order of magnitude higher than other nanowire lasers, Zhu says. Another exciting aspect of the lasers is that their color can be tuned simply by changing the composition of the (a) An 8.5-μm-long methylammonium lead iodide nanowire emits red laser light when excited by a 402-nm pulsed laser perovskite material. beam. (b) A 13.6-μm-long methylammonium lead bromide nanowire, meanwhile, lases green. Credit: Nature Materials.
ang Il Seok and his research team at the Korea Research Institute of Chemical Technology have made perovskite solar cells that have a record 20.1% certified power-conversion efficiency. This efficiency competes with that of commercial silicon solar cells. Last year, the South Korean team combined the most widely used perovskite, methylammonium lead halide, with formamidinium lead iodide to
higher efficiency photovoltaic devices. But uniform, dense fi lms of formamidinium lead iodide have been challenging to make. Seok and his colleagues placed a lead(II) iodide– dimethylsulfoxide (DMSO) film into a formamidinium iodide (FAI) solution. An intramolecular exchange results in FAI replacing DMSO in the lattice, resulting in a very high-quality formamidinium lead triiodide film.
Prachi Patel, [email protected] Pabitra K. Nayak, [email protected]
MRS BULLETIN
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VOLUME 40 • AUGUST 2015
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www.mrs.org/bulletin
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