Bernard Grobéty

TL;DR: In this article, the authors present phase equilibria that provide models for interpreting mineral-fluid relationships in oceanic serpentinites and allow the simultaneous evaluation of the conditions for redox, hydration and carbonation processes.

TL;DR: In this paper, carbon nanotubes were grown by the decomposition of C2H2 over a thin catalyst film in order to investigate the growth mechanism of CNTs by chemical vapour deposition (CVD).

TL;DR: These experiments suggest that ROS formation may play an important role in the genotoxicity of magnetite in A549 cells but that activation of JNK seems to be ROS-independent.

TL;DR: In this paper, the authors defined microstructure parameters, which control the effective transport properties in porous materials for energy technology, and proposed a procedure for quantitative analysis of constrictivity, which characterizes the bottleneck effect.

Abstract: approach to enhance the stability of the material under device working condition, i.e., light and thermal stress.[6,7] ABX3 halide perovskites most commonly used in solar cells contain cesium, methylammonium (MA) and formamidinium (FA) in the A site, Pb in the B, and Br and I in the X site of the crystalline lattice.[1,8–10] Compositions based on organic cations, such as MA and FA, can be prepared with a bandgap of around 1.5 eV, which is suited for an efficient single junction solar cell.[11] However, the presence of organic cations, and in particular the volatile MA, is linked to the relatively poor thermal stability and the high sensitivity to humid air, which affect most of the perovskite compositions employed in highly efficient PSCs.[12–16] Swapping entirely or in part the organic with inorganic cations, such as cesium (Cs), can help to enhance the stability of halide perovskites at the cost of a bandgap higher than 1.5,[17,18] which is suboptimal for a single junction solar cells. For example, the fully inorganic CsPbI3 perovskite has a bandgap of 1.7 eV, which is not optimal for single junction but is instead nearly ideally suited for perovskite–silicon tandem solar cell.[19–21] Unfortunately, CsPbI3 is only stable in the photovoltaic active perovskite structure – black phase – at temperatures above 300 °C,[22–25] which is not useful for applications. Partially (or completely) replacing iodide (I) with bromide (Br), i.e., exploring CsPbIxBr(3−x) compositions, can stabilize the active photovoltaic phase at room temperature with progressively increasing bandgap as the bromine content increases. This mixed halide approach is extensively used to prepared stable inorganic halide perovskite both for photo voltaic and light emitting devices.[26–32] As restricted to photovoltaics, it is a challenge controlling the interplay between phase stability, which can be obtained by enhancing the Br content, while maintaining the smallest possible bandgap. Indeed, the larger ionic radius of I as compared to Br upsets the stability perovskite, which tends to relax in a photovoltaic inactive delta phase.[33–37] The I/Br ratio must be therefore adjusted to achieve the lowest possible bandgap without sacrificing the perovskite phase stability. In the search for the best I/Br ratio, CsPbI2Br (I 67%, Br 33%) has been so far indicated as the optimum to achieve the highest efficiency PSC with a stable inorganic perovskite.[34–38] Liu et al. reported Organic–inorganic perovskite solar cells have achieved impressive power conversion efficiency over the past years, yet operational stability remains the key concern. One strategy to improve long-term stability is to replace the thermally unstable organic with inorganic cations comprising the perovskite lattice. Here, for the first time, pulsed infrared light is used to drive the crystallization of inorganic mixed halide CsPbIxBr(3−x) perovskite films in solar cells with a power conversion efficiency exceeding 10%. By varying the iodide–bromine ratio systematically, it is found that to keep the inorganic perovskite black phase stable at the room temperature, the iodine content needs to be limited to lower than 60% – bromine content higher than 40%. The finding revises previous reports claiming stable compositions with higher iodine contents, which is systematically exploited to reduce the perovskite bandgap with the aim to enlarge the light absorption spectra and thus to boost the device efficiency. It is demonstrated that the newly defined stable compositional range enables devices that retain 90% of the efficiency after stressing the perovskite at 200 °C for 1 h. This result demonstrates that inorganic halide perovskites are stable materials for high-temperature applications such as concentrated photovoltaics.