Development of tin halide perovskites is limited by the extremely poor stability and high background carrier density. Here, based on a pseudohalogen ''catalyst,'' we fabricated a Sn-based hierarchy structure perovskite in a one-step process, comprising highly parallel-orientation 2D PEA 2 SnI 4 on the surface of 3D FASnI 3 . The hierarchy structure delivers significantly enhanced stability and oxidation resistance in air atmosphere. We then explored hierarchy structure perovskite films in planar structure solar cells and achieved a PCE up to 9.41%. HIGHLIGHTS 2D-quasi-2D-3D hierarchy structure perovskite is fabricated for the first time Removable pseudohalogen acts as a regulator to manipulate tin perovskite structureThe hierarchy structure effectively resists oxidation and increases carrier mobilityThe hierarchy structure tin perovskite solar cells achieve a record PCE of 9.41% Wang et al., Joule SUMMARYThe power conversion efficiency (PCE) of tin perovskite solar cells is impeded by the extremely poor resistance to oxidation and high density of intrinsic Sn vacancies. Herein, we grow a 2D-quasi-2D-3D Sn perovskite film using removable pseudohalogen NH 4 SCN as a structure regulator. This hierarchy structure remarkably enhances air stability resulting from the parallel growth of 2D PEA 2 SnI 4 as the surface layer. We then explore the hierarchy structure perovskite films in planar structural solar cells, which generate a PCE up to 9.41%. The device retains 90% of its initial performance for almost 600 hr. Our results suggest that adding removable NH 4 SCN in a perovskite precursor can significantly improve the stability and photovoltaic performance of Sn perovskite. This finding provides a powerful strategy to manipulate the structure of low-dimensional perovskite in order to enhance the performance of perovskite solar cells.

Construction of thermally and chemically robust metal−organic frameworks (MOFs) is highly desirable for postcombustion CO 2 capture from flue gas containing water vapor and other acidic gases. Here we report a strategy based on appending amino groups to the triazolate linkers of MOFs to achieve exceptional chemical stability against aqueous, acidic, and basic conditions. These MOFs exhibit not only CO 2 /N 2 thermodynamic adsorption selectivity as high as 120 but also CO 2 /H 2 O kinetic adsorption selectivity up to 70, featuring distinct adsorptive sites at the channel center for CO 2 and at the corner for H 2 O, respectively. The best performing MOF in this series features low regeneration energy, high CO 2 capture utility under humid conditions, and decent cycling performance for mimic flue gas.M etal−organic frameworks (MOFs) are prominent solid adsorbents that combine well-defined adsorptive sites, fine-tuned pore sizes, and decorated interior functionalities to achieve strong binding affinity, high selectivity, large capacity, and low regeneration energy for CO 2 capture. 1−3 However, with respect to practical postcombustion capture, concerns arise from the competitive adsorption of H 2 O against CO 2 4

Scaling in membrane distillation (MD) is a key issue in desalination of concentrated saline water, where the interface property between the membrane and the feed become critical. In this paper, a new slippery mechanism was explored as an innovative concept to understand the scaling behavior in membrane distillation for a soluble salt, NaCl. The investigation was based on a novel design of a superhydrophobic polyvinylidene fluoride (PVDF) membrane with micro-pillar arrays (MP-PVDF) using a micromolding phase separation (µPS) method. The membrane showed a contact angle of 166.0 ± 2.3° and the sliding angle of 15.8 ± 3.3°. After CF4 plasma treatment, the resultant membrane (CF4-MP-PVDF) showed a reduced sliding angle of 3.0 o. In direct contact membrane distillation (DCMD), the CF4-MP-PVDF membrane illustrated excellent anti-scaling in concentrating saturated NaCl feed. Characterization of the used membranes showed that scaling due to NaCl crystals and possible membrane wetting occurred on the control PVDF and MP-PVDF membranes, but not on the CF4-MP-PVDF membrane. To understand this phenomenon, a "slippery" theory was introduced and correlated the sliding angle to the slippery surface of CF4-MP-PVDF and its anti-scaling property. This work provides a well-defined physical and theoretical platform for investigating scaling problems in membrane distillation and beyond.

[1] We have constructed expressions of the relativistic diffusion coefficients in both pitch angle and momentum resulting from gyroresonant interactions between electrons and superluminous (R-X, L-O, L-X) wave modes that are generated as auroral kilometric radiation (AKR) in the Earth's magnetosphere. Detailed analysis is made of wave resonant frequencies for each given harmonic n, electron energy, wave normal angles for two typical regions of the magnetosphere: the higher-density region h = jW e j 2 /w 2 pe < 1 (e.g., near the geostationary orbit) and the lower-density region h > 1 (e.g., at the high latitude of the radiation belts), where jW e j and w pe are the electron gyrofrequency and the plasma frequency. The resonant frequency range in the higher-density region is found to be generally smaller than that in the lower-density region, and the efficient electron gyroresonance with the superluminous wave modes occurs mainly at the higher harmonics, e.g., jnj ! 3. In contrast to the subluminous waves, e.g., chorus which has easily up to three resonant frequencies, only one or two resonant frequencies were found for superluminous waves at each combination of wave and particle parameters of interest. Numerical calculations for diffusion coefficients of the momentum D pp , the pitch angle D aa , and the mixed D pa are performed specifically for the two typical regions above. It is found that the momentum diffusion generally dominates over the pitch angle diffusion, namely, D pp > jD pa j > D aa for the pitch angle a above a critical angle a c , whereas D aa generally dominates below the critical angle a c . Specifically, D pp /D aa can exceed 10 for a > a c % 7.5°and h = 0.2, while for a > a c % 30°and h = 20. This is a new result in contrast to the case of subluminous waves (e.g., whistler mode waves) in which basically D aa > jD pa j> D pp . We have also presented some estimates regarding what wave amplitudes are required to produce particular acceleration timescales and found that the required wave amplitudes in the lower-density region are much lower than those in the higher-density region. The results suggest that superluminous wave modes may contribute significantly to both the stochastic acceleration of trapped electrons (with larger pitch angle) and the loss process of untrapped electrons (with smaller pitch angles) during magnetic storms if those waves are found to be present in the radiation belts of the Earth, but this needs to be further investigated.Citation: Xiao, F., H. He, Q. Zhou, H. Zheng, and S. Wang (2006), Relativistic diffusion coefficients for superluminous (auroral kilometric radiation) wave modes in space plasmas,

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[1] The well-known generalized Lorentzian (kappa) distribution generally provides a good representation for the high-energy tail population of natural cosmic suprathermal plasmas. In this study we examine the electromagnetic ion cyclotron waves (EMIC) instability driven by the temperature anisotropy condition (T ? /T k > 1) of suprathermal protons modeled with a typical kappa distribution in a cold multispecies plasma (electron, H + , He + , and O + ). Since the EMIC wave instability is found to be significant typically above the O + band, we apply a linear theory to study the instability threshold condition for the He + and H + bands particularly around the geostationary orbit. The instability threshold condition, as in the case for a regular bi-Maxwellian, is found to follow a typical form T ? /T k À 1 = S/b k a , with higher values in the He + band than those in the H + band in the case of the strong wave instability owing to a lower maximum wave growth in the He + band. As the spectral index k increases, the instability threshold condition generally decreases and tends to the lowest limiting values of the bi-Maxwellian, since the evaluation by the bi-Maxwellian generally overestimates the maximum wave growth. The densities of the cold components (particularly protons) have impacts on the threshold condition primarily in the H + band, with a higher density of cold protons leading to a lower value of the threshold condition. The results above may further reveal the nature of this instability threshold condition for the EMIC waves in any other space plasmas where an anisotropic suprathermal ion component and cold multicomponents are present together.

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