RESEARCH HIGHLIGHTS: Perovskites
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RESEARCH HIGHLIGHTS :
Perovskites
By Prachi Patel Feature Editor: Pabitra K. Nayak
Research on perovskites has progressed rapidly since the first perovskite-based solar cells with ~4% efficiency were reported in 2009. MRS Bulletin presents a selection of recent advances in this burgeoning field.
T
he discovery of a rare property in perovskites has allowed researchers to rapidly grow centimeter-scale, goodquality single crystals of the material. Salts generally tend to dissolve more in a solvent when temperature increases. But a few research groups have independently found that the solubility of perovskites in certain solvents decreases with a rise in temperature, leading to the formation of single crystals in the solution at high temperatures. While conventional growth methods take weeks to grow such large crystals, the new method yields results in just a few hours. This finding could lead to perovskite single-crystal-based optoelectronic devices with superior performances. Salts generally tend to dissolve faster in a solvent when temperature increases. But a few research groups have independently found that the solubility of perovskites in certain solvents decreases with rise in temperature, leading to the
formation of single crystals in the solution at high temperatures. Researchers at the Swiss Federal Institute of Technology in Lausanne reported the phenomenon in perovskites in Scientific Reports (DOI: 10.1038/ srep11654). The research team, led by chemical science and engineering professor Anders Hagfeldt, found that heating a concentrated (1:1 molar ratio) solution of methylammonium iodide and lead iodide in the solvent gamma γ-butyrolactone (GBL) to 190°C led to the formation of freestanding methylammonium lead iodide (CH3NH3PbI3) perovskite crystals. Once the crystals reached the desired size, the researchers removed them from the hot solution because the crystals dissolve back into the solution upon cooling. They report making crystals over 1-mm long in 25 minutes. This initial report was followed by similar advances published in Nature Communications (DOI: 10.1038/
ncomms8586) by a group at the King Abdullah University of Science and Technology (KAUST), and then in Advanced Materials (DOI: 10.1002/ adma.201502597) by researchers at the Shaanxi Normal University in Xi’an, China. Materials science and engineering professor Osman Bakr and his colleagues at KAUST reported the crystallization of CH3NH3PbBr3 from N,N-dimethylformamide solvent and the creation of CH3NH3PbI3 crystals from GBL. They calculated the speed of crystal growth to be as high as 20 mm3/h for CH3NH3PbI3 and 38 mm3/h for CH3NH3PbBr3. Conventional solution growth gives a highest speed of 1 mm3/h. Meanwhile, Zhou Yang, Shengzhong (Frank) Liu, and their colleagues at Shaanxi Normal University were able to grow CH3NH3PbI3 crystals with a diagonal length of 28 mm in 12 hours and crystals as large as 71 mm (over 2.5 in.) in length over a period of 48 hours.
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colors, photodetectors employ expensive optical filters that require complicate
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