Advanced instrumentation enables continuous high-resolution x-ray ptychography
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erovskite solar cells are prone to degradation when exposed to humidity and sunlight, and researchers have been devising various ingenuous ways to improve their stability. A University of Oxford research team led by Sai Bai, Feng Gao, and Henry Snaith have found that adding ionic liquids to perovskites markedly improves the devices’ long-term stability. The researchers added the ionic liquid 1-butyl-3-methylimidazolium
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esearchers at Kyushu University in Japan have made exceptionally thick organic light-emitting diodes (OLEDs) by combining thin organic light-emitting films with hybrid perovskite charge-transport layers. They published their results in Nature (doi:10.1038/s41586-019-1435-5). OLEDs hold promise for low-cost, flexible displays and lighting. They are made of
Advanced instrumentation enables continuous highresolution x-ray ptychography
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-ray ptychography differs from more commonly known x-ray techniques that rely on attenuation in x-ray intensity to detect matter. In contrast, ptychography functions on diffraction of coherent x-rays. Diffraction patterns result from interference (i.e., superposition) of x-rays scattered by the structural features of the material under investigation. Accordingly, ptychography can provide information at much smaller dimensions than radiography. In principle, this diffraction imaging technique offers wavelength-limited resolution. However, in practice, spatial resolutions are also limited by inaccuracies while positioning the incident beam. Junjing Deng and his colleagues at Argonne National Laboratory have introduced an instrument called the Velociprobe to relax this limitation and advance ptychography imaging. They reported this design in a recent issue of the Review of Scientific Instruments (doi:10.1063/1.5103173).
tetrafluoroborate to the formamidinium-methylammonium-cesium lead halide perovskite. They made a solar cell by using this light-absorbing layer between electron and hole extraction layers. The most stable encapsulated devices lost just 5% of their roughly 20% power-conversion efficiency after being exposed to simulated sunlight for more than 1800 hours at 70–75°C. The team estimates that device efficiency drops to
80% of its peak performance in about 5200 hours. Ions migrate in the perovskite layer, especially under light and heat, creating defects that can trap charges and bring down efficiency. The ionic liquid unpredictably suppressed this ion migration, and it also facilitates better charge transfer between the perovskite and charge-transport layer, the team reported in a recent issue of Nature (doi:10.1038/s41586-019-1357-2).
a layer of organic light-emitting molecules sandwiched between organic charge-transport layers. The transport layers need to be thick to completely cover the defects and residues on a substrate. But this requires high driving voltage because organic materials are usually poor conductors. Toshinori Matsushima, Chihaya Adachi, and their colleagues used the
perovskite methylammonium lead chloride to make transport layers t
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