2016 Nobel Prizes in physics and chemistry: A materials view
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niversity of Oxford researchers have shed light on how perovskites rapidly form macroscopic single crystals at high temperatures from solution. Using this knowledge, they were able to produce higher quality single crystals
than ones made so far using the rapid crystallization technique. Henry Snaith and his colleagues report in Nature Communications (doi:10.1038/ ncomms13303) that perovskite crystallization is triggered by a change in the acid–base equilibrium of the solvent,
which raises the concentration of the solute and results in the perovskite’s quick saturation out of the solution as crystals. Understanding the factors that influence and control crystallization is key to making high-performance perovskite optoelectronic devices.
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ncreasing the stability of perovskites is another key requirement for their commercial success. Michael Grätzel and co-workers at the École Polytechnique Fédérale de Lausanne, Switzerland have now made highly stable, efficient solar cells by integrating rubidium into lead-halide perovskite films.
The resulting solar cells have a power-conversion efficiency of 21.6%. They maintain 95% of their initial performance over 500 continuous hours under full sunlight at 85°C. Earlier this year, the researchers reported a triple-cation (methylammonium, formamidinium, and cesium) perovskite, yielding a solar efficiency
of 21.2% that remained stable for 250 hours. The new advance published in Science (doi:10.1126/science. aah5557) takes that work a step further. This time they added rubidium to the mix. The rubidium cations may help relax lattice strain, giving a more defect-free crystal, says the lead author Michael Saliba.
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searchers, led by Joseph M. Luther at the National Renewable Energy Laboratory, made a thin film of nanocrystals of the perovskite cesium lead iodide (CsPbI3) with good electronic coupling among the quantum dots. Low-bandgap all-inorganic perovskites such as CsPbI3 were thought to be stable only at temperatures over 600°F. But the team discovered a method to
keep nanocrystals of the material stable at room temperature, which they detail in Science (doi:10.1126/science. aag2700). They first mixed a Cs-oleate solution with a PbI2 precursor. They then purifi ed the nanocrystals using methyl acetate as an anti-solvent that removed excess unreacted precursors, which turned out to be critical to increasing their stability.
esearchers have used perovskite quantum dots in solar cells to get a relatively high power-conversion efficiency of 10.77%. This is comparable to efficiencies of quantum dot solar cells made of other materials, and higher than that of other reported all-inorganic perovskite solar cells. Quantum dots are nanocrystals of semiconductor materials. The re-
2016 Nobel Prizes in physics and chemistry: A materials view Prachi Patel
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his year’s Nobel Prizes in Chemistry and Physics, which honor the use of topological concepts, were also a win for materials science and materials research. The 2016 Nobel Prize in Physics was awarded to David J. Thouless
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