Intrinsic Halide Segregation at Nanometer Scale Determines the High Efficiency of Mixed Cation/Mixed Halide Perovskite Solar Cells.

Compositional engineering of a mixed cation/mixed halide perovskite in the form of (FAPbI3)0.85(MAPbBr3)0.15 is one of the most effective strategies to obtain record-efficiency perovskite solar cells. However, the perovskite self-organization upon crystallization and the final elemental distribution, which are paramount for device optimization, are still poorly understood. Here we map the nanoscale charge carrier and elemental distribution of mixed perovskite films yielding 20% efficient devices. Combining a novel in-house-developed high-resolution helium ion microscope coupled with a secondary ion mass spectrometer (HIM-SIMS) with Kelvin probe force microscopy (KPFM), we demonstrate that part of the mixed perovskite film intrinsically segregates into iodide-rich perovskite nanodomains on a length scale of up to a few hundred nanometers. Thus, the homogeneity of the film is disrupted, leading to a variation in the optical properties at the micrometer scale. Our results provide unprecedented understanding of the nanoscale perovskite composition.

In-situ Isotopic Analysis at Nanoscale using Parallel Ion Electron Spectrometry: A Powerful New Paradigm for Correlative Microscopy.

Isotopic analysis is of paramount importance across the entire gamut of scientific research. To advance the frontiers of knowledge, a technique for nanoscale isotopic analysis is indispensable. Secondary Ion Mass Spectrometry (SIMS) is a well-established technique for analyzing isotopes, but its spatial-resolution is fundamentally limited. Transmission Electron Microscopy (TEM) is a well-known method for high-resolution imaging down to the atomic scale. However, isotopic analysis in TEM is not possible. Here, we introduce a powerful new paradigm for in-situ correlative microscopy called the Parallel Ion Electron Spectrometry by synergizing SIMS with TEM. We demonstrate this technique by distinguishing lithium carbonate nanoparticles according to the isotopic label of lithium, viz. (6)Li and (7)Li and imaging them at high-resolution by TEM, adding a new dimension to correlative microscopy.

A comparison of mountain rescue casualty bags in a cold, windy environment.

OBJECTIVE: To help the Mountain Rescue Association of Scotland find the best protective mountain rescue casualty bag in cold and windy conditions. The study investigated how 3 different casualty bags (labeled Bag 1, Bag 2, and Bag 3) performed in a cold (-10 degrees C, dry bulb), windy (wind speed 3.0 m x s(-1)) environment using physiological and subjective responses of the participating subjects. METHODS: Eleven male subjects, aged 23.4+/-4 years, percentage body fat 15.5+/-2 (mean +/- SD). Each participated in a total of 3 tests (1 for each bag). The tests were scheduled to last 60 minutes. Core and skin temperatures (skin values were measured on the arm, chest, thigh, and calf, and a mean skin temperature was calculated) were measured during the tests. Heart rate, oxygen consumption (Vo2), and subjective cold perception ratings were also recorded at regular intervals throughout the test duration. All variables except for Vo2 and cold discomfort were adjusted for baseline. RESULTS: There was a significant difference in the mean response between the bags for the following variables: arm, chest, thigh, calf, mean temperature, and cold discomfort. CONCLUSIONS: All 3 bags showed limited ability to protect the subjects in cold, windy conditions. However, the study shows that Bag 2 offered the least protection against the imposed environment. It is difficult to differentiate between the other 2 bags, because Bag 1 performed better than Bag 3 for arm, calf, and mean temperatures, while Bag 3 outperformed Bag 1 for chest and thigh temperatures and cold discomfort scores.