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1. Merits and Challenges of Ruddlesden–Popper Soft Halide Perovskites in Electro‐Optics and Optoelectronics

   https://doi.org/10.1002/adma.201803514  

   Chen, Zhizhong ; Guo, Yuwei ; Wertz, Esther ; Shi, Jian ( October 2018 , Advanced Materials)

   Following the rejuvenation of 3D organic–inorganic hybrid perovskites, like CH₃NH₃PbI₃, (quasi)‐2D Ruddlesden–Popper soft halide perovskites R₂A_n−1Pb_nX_3n+1have recently become another focus in the optoelectronic and photovoltaic device community. Although quasi‐2D perovskites were first introduced to stabilize optoelectronic/photovoltaic devices against moisture, more interesting properties and device applications, such as solar cells, light‐emitting diodes, white‐light emitters, lasers, and polaritonic emission, have followed. While delicate engineering design has pushed the performance of various devices forward remarkably, understanding of the fundamental properties, especially the charge‐transfer process, electron–phonon interactions, and the growth mechanism in (quasi)‐2D halide perovskites, remains limited and even controversial. Here, after reviewing the current understanding and the nexus between optoelectronic/photovoltaic properties of 2D and 3D halide perovskites, the growth mechanisms, charge‐transfer processes, vibrational properties, and electron–phonon interactions of soft halide perovskites, mainly in quasi‐2D systems, are discussed. It is suggested that single‐crystal‐based studies are needed to deepen the understanding of the aforementioned fundamental properties, and will eventually contribute to device performance.

    

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2. Kinetics and Mechanism of the Gold‐Catalyzed Hydroamination of 1,1‐Dimethylallene with N ‐Methylaniline

   https://doi.org/10.1002/chem.202100741  

   Harris, Robert J. ; Nakafuku, Kohki ; Duncan, Alethea N. ; Carden, Robert G. ; Timmerman, Jacob C. ; Widenhoefer, Ross A. ( June 2021 , Chemistry – A European Journal)

   The mechanism of the intermolecular hydroamination of 3‐methylbuta‐1,2‐diene (1) withN‐methylaniline (2) catalyzed by (IPr)AuOTf has been studied by employing a combination of kinetic analysis, deuterium labelling studies, and in situ spectral analysis of catalytically active mixtures. The results of these and additional experiments are consistent with a mechanism for hydroamination involving reversible, endergonic displacement ofN‐methylaniline from [(IPr)Au(NHMePh)]⁺(4) by allene to form the cationic gold π‐C1,C2‐allene complex [(IPr)Au(η²‐H₂C=C=CMe₂)]⁺(I), which is in rapid, endergonic equilibrium with the regioisomeric π‐C2,C3‐allene complex [(IPr)Au(η²‐Me₂C=C=CH₂)]⁺(I′). Rapid and reversible outer‐sphere addition of2to the terminal allene carbon atom ofI′to form gold vinyl complex (IPr)Au[C(=CH₂)CMe₂NMePh] (II) is superimposed on the slower addition of2to the terminal allene carbon atom ofIto form gold vinyl complex (IPr)Au[C(=CMe₂)CH₂NMePh] (III). Selective protodeauration ofIIIreleasesN‐methyl‐N‐(3‐methylbut‐2‐en‐1‐yl)aniline (3 a) with regeneration of4. At high conversion, gold vinyl complexIIis competitively trapped by an (IPr)Au⁺fragment to form the cationic bis(gold) vinyl complex {[(IPr)Au]₂[C(=CH₂)CMe₂NMePh]}⁺(6).

    

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3. Anisotropic Properties of Quasi‐1D In 4 Se 3 : Mechanical Exfoliation, Electronic Transport, and Polarization‐Dependent Photoresponse

   https://doi.org/10.1002/adfm.202106459  

   Vorobeva, Nataliia S. ; Lipatov, Alexey ; Torres, Angel ; Dai, Jun ; Abourahma, Jehad ; Le, Duy ; Dhingra, Archit ; Gilbert, Simeon J. ; Galiy, Pavlo V. ; Nenchuk, Taras M. ; et al ( September 2021 , Advanced Functional Materials)

   Theoretical and experimental investigations of various exfoliated samples taken from layered In₄Se₃crystals are performed. In spite of the ionic character of interlayer interactions in In₄Se₃and hence much higher calculated cleavage energies compared to graphite, it is possible to produce few‐nanometer‐thick flakes of In₄Se₃by mechanical exfoliation of its bulk crystals. The In₄Se₃flakes exfoliated on Si/SiO₂have anisotropic electronic properties and exhibit field‐effect electron mobilities of about 50 cm² V⁻¹ s⁻¹at room temperature, which are comparable with other popular transition metal chalcogenide (TMC) electronic materials, such as MoS₂and TiS₃. In₄Se₃devices exhibit a visible range photoresponse on a timescale of less than 30 ms. The photoresponse depends on the polarization of the excitation light consistent with symmetry‐dependent band structure calculations for the most expectedaccleavage plane. These results demonstrate that mechanical exfoliation of layered ionic In₄Se₃crystals is possible, while the fast anisotropic photoresponse makes In₄Se₃a competitive electronic material, in the TMC family, for emerging optoelectronic device applications.

    

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4. Monolayer Superconductivity and Tunable Topological Electronic Structure at the Fe(Te,Se)/Bi 2 Te 3 Interface

   https://doi.org/10.1002/adma.202210940  

   Moore, Robert G. ; Lu, Qiangsheng ; Jeon, Hoyeon ; Yao, Xiong ; Smith, Tyler ; Pai, Yun‐Yi ; Chilcote, Michael ; Miao, Hu ; Okamoto, Satoshi ; Li, An‐Ping ; et al ( April 2023 , Advanced Materials)

   The interface between 2D topological Dirac states and ans‐wave superconductor is expected to support Majorana‐bound states (MBS) that can be used for quantum computing applications. Realizing these novel states of matter and their applications requires control over superconductivity and spin‐orbit coupling to achieve spin‐momentum‐locked topological interface states (TIS) which are simultaneously superconducting. While signatures of MBS have been observed in the magnetic vortex cores of bulk FeTe_0.55Se_0.45, inhomogeneity and disorder from doping make these signatures unclear and inconsistent between vortices. Here superconductivity is reported in monolayer (ML) FeTe_1–ySe_y(Fe(Te,Se)) grown on Bi₂Te₃by molecular beam epitaxy (MBE). Spin and angle‐resolved photoemission spectroscopy (SARPES) directly resolve the interfacial spin and electronic structure of Fe(Te,Se)/Bi₂Te₃heterostructures. Fory = 0.25, the Fe(Te,Se) electronic structure is found to overlap with the Bi₂Te₃TIS and the desired spin‐momentum locking is not observed. In contrast, fory = 0.1, reduced inhomogeneity measured by scanning tunneling microscopy (STM) and a smaller Fe(Te,Se) Fermi surface with clear spin‐momentum locking in the topological states are found. Hence, it is demonstrated that the Fe(Te,Se)/Bi₂Te₃system is a highly tunable platform for realizing MBS where reduced doping can improve characteristics important for Majorana interrogation and potential applications.

    

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5. Oxygen‐Induced Structural Disruption for Improved Li + Transport and Electrochemical Stability of Li 3 PS 4

   https://doi.org/10.1002/aenm.202302785  

   Deck, Michael J. ; Chien, Po‐Hsiu ; Poudel, Tej P. ; Jin, Yongkang ; Liu, Haoyu ; Hu, Yan‐Yan ( December 2023 , Advanced Energy Materials)

   The performance of all‐solid‐state batteries (ASSBs) relies on the Li⁺transport and stability characteristics of solid electrolytes (SEs). Li₃PS₄is notable for its stability against lithium metal, yet its ionic conductivity remains a limiting factor. This study leverages local structural disorder via O substitution to achieve an ionic conductivity of 1.38 mS cm⁻¹with an activation energy of 0.34 eV for Li₃PS_4−xO_x(x = 0.31). Optimal O substitution transforms Li⁺transport from 2D to 3D pathways with increased ion mobility. Li₃PS_3.69O_0.31exhibits improvements in the critical current density and stability against Li metal and retains its electrochemical stability window compared with Li₃PS₄. The practical implementation of Li₃PS_3.69O_0.31in ASSBs half‐cells, particularly when coupled with TiS₂as the cathode active material, demonstrates substantially enhanced capacity and rate performance. This work elucidates the utility of introducing local structural disorder to ameliorate SE properties and highlights the benefits of strategically combining the inherent strengths of sulfides and oxides via creating oxysulfide SEs.

    

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