Bio Focus: Cryo-transmission electron microscopy reveals protein nucleation pathways
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ust as for humans, allowing perovskites to soak up sun helps them to relax and makes them more efficient. Constantly illuminating a triple-cation hybrid perovskite thin film expands its crystal lattice, which relaxes strain, researchers report in Science (doi: 10.1126/ science.aap8671). This, in turn, aligns the material’s crystal planes and repairs defects, as well as lowers the
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hile halide perovskites are making strides toward commercial devices, their inorganic perovskite oxide counterparts have also attracted attention for solar cells. Devices made from these ferroelectric perovskites are highly stable and have high opencircuit voltages, but they have shown limited efficiencies.
energy barrier at the perovskite-contact interface, improving the material’s power-conversion efficiency. Recent studies have shown that lightinduced structural changes play an important role in the optoelectronic properties and stability of devices. But such studies on mixed-cation halide perovskites are lacking. Wanyi Nie, Aditya Mohite, and their colleagues at Los Alamos National
Laboratory illuminated formamidiniummethylammonium cesium lead iodide perovskite thin films using a standard 1-sun source for 180 minutes. The efficiency of solar cells made with the films went up from 18.5% to 20.5%. Light soaking did not compromise the cells’ stability: they worked with minimal degradation for 1500 hours under standard full-spectrum solar illumination.
In a Nature Photonics (doi:10.1038/ s41566-018-0137-0) paper, Canadian researchers demonstrate an alternative route to making high-performance solar cells from perovskite oxides. They made a device from a composite bismuthmanganese-oxide thin film with two different crystal phases—BiMnO3 and BiMn2O5—which had a power-con-
version efficiency of around 4.2%. Inorganic perovskite oxides are ferroelectric. They do not conduct charge carriers well, leading to low photocurrent density and hence low efficiency. But in the mixed material, ferroelectric BiMnO3 grains are incorporated into semiconducting BiMnO5, which boosts photocurrent density.
Bio Focus Cryo-transmission electron microscopy reveals protein nucleation pathways
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ucleation is the initial stage of crystallization, a process in which individual building blocks (e.g., atoms and molecules) assemble into various crystalline structures, or “polymorphs.” Polymorphs usually exhibit different physiochemical properties due to their diverse structures, and hence are suitable platforms to demonstrate “structure–function” relationships. Therefore, understanding the nucleation and crystallization mechanisms leading to distinct polymorphs is critical. Now, by using cryotransmission electron microscopy (cryoTEM), a group of researchers—from the Centre Nacional de la Recherche Scientifique–Université Grenoble Alpes, France; Technische Universiteit Eindhoven, The Netherlands; and the Vrije Universiteit Brussel, Belgium—has directly observed how the protein glucose isomerase nucleates as different polymorphs. Their findings were recently p
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