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Liquid metals (LMs) are emerging as unique fluids for a variety of applications, but their nanoscale solvation properties remain largely understudied. In this work, a combination of atomic force microscopy (AFM) and molecular dynamics (MD) simulations are used to investigate the structure of the interface between the bulk room temperature liquid metal (RTLM) and the LM oxide in nanodroplet systems of gallium, EGaIn (75.5% gallium, 24.5% indium), and Galinstan (68.5% gallium, 21.5% indium, 10% tin). Field's metal (51% indium, 32.5% bismuth, 16.5% tin) is also investigated, which melts at ≈62 °C, as a contrast to the other systems. AFM measurements reveal distinct sub‐oxide nanostructured layering in all three RTLM systems, and Field's metal above the melting point, to differing degrees. EGaIn and Galinstan show multiple penetration events between 20 and 30 nm, with smaller, less complex events in Ga. MD simulations suggest that this layering is a result of the near‐surface ordering of LM atoms beneath the oxide layer. Importantly, the atoms in this region do not behave as solids but are more ordered than in a pure disordered liquid system. The surface nanostructure elucidated here significantly expands the understanding of LM systems and their behavior at interfaces. [ABSTRACT FROM AUTHOR]

Crystallization of alloys from a molten state is a fundamental process underpinning metallurgy. Here the direct imaging of an intermetallic precipitation reaction at equilibrium in a liquid‐metal environment is demonstrated. It is shown that the outer layers of a solidified intermetallic are surprisingly unstable to the depths of several nanometers, fluctuating between a crystalline and a liquid state. This effect, referred to herein as crystal interface liquefaction, is observed at remarkably low temperatures and results in highly unstable crystal interfaces at temperatures exceeding 200 K below the bulk melting point of the solid. In general, any liquefaction process would occur at or close to the formal melting point of a solid, thus differentiating the observed liquefaction phenomenon from other processes such as surface pre‐melting or conventional bulk melting. Crystal interface liquefaction is observed in a variety of binary alloy systems and as such, the findings may impact the understanding of crystallization and solidification processes in metallic systems and alloys more generally. [ABSTRACT FROM AUTHOR]

Inorganic lead‐free halide perovskites, devoid of toxic or rare elements, have garnered considerable attention as photocatalysts for pollution control, CO2 reduction and hydrogen production. In the extensive perovskite design space, factors like substitution or doping level profoundly impact their performance. To address this complexity, a synergistic combination of machine learning models and theoretical calculations were used to efficiently screen substitution elements that enhanced the photoactivity of substituted Cs2AgBiBr6 perovskites. Machine learning models determined the importance of d10 orbitals, highlighting how substituent electron configuration affects electronic structure of Cs2AgBiBr6. Conspicuously, d10‐configured Zn2+ boosted the photoactivity of Cs2AgBiBr6. Experimental verification validated these model results, revealing a 13‐fold increase in photocatalytic toluene conversion compared to the unsubstituted counterpart. This enhancement resulted from the small charge carrier effective mass, as well as the creation of shallow trap states, shifting the conduction band minimum, introducing electron‐deficient Br, and altering the distance between the B‐site cations d band centre and the halide anions p band centre, a parameter tuneable through d10 configuration substituents. This study exemplifies the application of computational modelling in photocatalyst design and elucidating structure–property relationships. It underscores the potential of synergistic integration of calculations, modelling, and experimental analysis across various applications. [ABSTRACT FROM AUTHOR]

Organic–inorganic perovskite solar cells (PSCs) are promising candidates for next‐generation, inexpensive solar panels due to their commercially competitive cost and high power conversion efficiencies. However, PSCs suffer from poor stability. A new and vast subset of PSCs, quasi‐two‐dimensional Ruddlesden–Popper PSCs (quasi‐2D RP PSCs), has improved photostability and superior resilience to environmental conditions compared to three‐dimensional metal‐halide PSCs. To accelerate the search for new quasi‐2D RP PSCs, this work reports a combinatorial, machine learning (ML) enhanced high‐throughput perovskite film fabrication and optimization study. This work designs a bespoke experimental strategy and produces perovskite films with a range of different compositions using only spin‐coating free, reproducible robotic fabrication processes. The performance and characterization data of these solar cells are used to train a ML model that allow materials parameters to be optimized and direct the design of improved materials. The new, ML‐optimized, drop‐cast quasi‐2D RP perovskite films yield solar cells with power conversion efficiencies of up to 16.9%. [ABSTRACT FROM AUTHOR]

The functionalization of small‐molecule hole‐transport materials (HTMs) heavily relies on the rational design of molecular geometry, which can optimize both intrinsic HTM properties and interfacial properties for realizing high‐performance and stable lead halide perovskite solar cells (LHPSCs). Herein, two fluorene‐based donor–π linker–donor HTMs are seen, FL01 and FL02, whose side chains are tailored with planar phenyl‐carbazole groups and twisted triphenylamine groups, respectively. Benefiting from the high conformational flexibility of twisted side chains, the strong and oriented interaction via PbO bonding is well coordinated at the perovskite and FL02 interface, which favors the interfacial charge transfer as well as the protection of perovskite layer by effectively blocking or mitigating the diffusion of hygroscopic dopants toward the perovskite surface. Consequently, the performance of FL02 HTM‐based n–i–p LHPSCs is significantly enhanced by achieving a power conversion efficiency of 17.8%, which is twice higher than that (8.6%) of FL01 HTM‐based ones and comparable with the case (18.8%) of conventional spiro‐OMeTAD HTM‐based devices. More importantly, the FL02‐based devices exhibit impressively high operation and storage stabilities with T80 and TS80 lifetimes of >98 h and ≈270 days, respectively, which are among the longest lifespans for the type of hygroscopically doped LHPSCs. [ABSTRACT FROM AUTHOR]

Miniaturization and energy consumption by computational systems remain major challenges to address. Optoelectronics based synaptic and light sensing provide an exciting platform for neuromorphic processing and vision applications offering several advantages. It is highly desirable to achieve single‐element image sensors that allow reception of information and execution of in‐memory computing processes while maintaining memory for much longer durations without the need for frequent electrical or optical rehearsals. In this work, ultra‐thin (<3 nm) doped indium oxide (In2O3) layers are engineered to demonstrate a monolithic two‐terminal ultraviolet (UV) sensing and processing system with long optical state retention operating at 50 mV. This endows features of several conductance states within the persistent photocurrent window that are harnessed to show learning capabilities and significantly reduce the number of rehearsals. The atomically thin sheets are implemented as a focal plane array (FPA) for UV spectrum based proof‐of‐concept vision system capable of pattern recognition and memorization required for imaging and detection applications. This integrated light sensing and memory system is deployed to illustrate capabilities for real‐time, in‐sensor memorization, and recognition tasks. This study provides an important template to engineer miniaturized and low operating voltage neuromorphic platforms across the light spectrum based on application demand. [ABSTRACT FROM AUTHOR]

Gallium nitride (GaN) technology has matured and commercialised for optoelectronic devices in the ultraviolet (UV) spectrum over the last few decades. Simultaneously, atomically thin materials with unique features have emerged as contenders for device miniaturization. However, the lack of successful techniques to produce ultra‐thin GaN prevents access to these new predicted properties. Here, this important gap is addressed by printing millimeter‐large ultra‐thin GaN nanosheets (NS) (≈1.4 nm) using a simple two‐step process that simultaneously introduces nitrogen point defects. This extends the photoelectrical spectral response from UV (280 nm) to near infrared (NIR) (1080 nm). The GaN‐based photodetectors display excellent figures of merit, having a responsivity (2.72 × 104 A W−1) up to four orders of magnitude higher than the commercial photodetectors at room temperature, despite being 102–103 times thinner. The photodetectors exhibit fast switching, with rise and decay time in the range of microseconds. The state‐of‐the‐art device performance originates from the ultra‐thin nature of GaN NS coupled with nitrogen point vacancies in the synthesis process. This work presents the opportunity to significantly expand the reach of GaN semiconductor technology and may lead to applications in high‐performance miniaturized imaging systems, spectroscopy, communication, and integrated optoelectronic circuits. [ABSTRACT FROM AUTHOR]

Designing dopant‐free small‐molecule hole transport materials (HTMs) with self‐assembly behavior via noncovalent interactions is considered as one effective strategy to achieve high‐performance inverted perovskite solar cells (PSCs). Herein, two donor‐π bridge‐donor (D–π–D) HTMs are presented, TPASF and TPAOF, containing 3,6‐dimethoxythieno[3,2‐b]thiophene as a core part with 3‐fluoro‐N,N‐bis(4‐(methylthio)phenyl)aniline and 3‐fluoro‐N,N‐bis(4‐methoxyphenyl)aniline as side group. The synergistic F⋅⋅⋅S dipole–dipole intra‐ and intermolecular interactions in TPASF drive the self‐assembly of this molecule into a supramolecular nanofibrillar network, leading to high hole mobility, superior interfacial properties, and providing a good growth template for the perovskite layer atop. The corresponding dopant‐free TPASF‐based inverted devices exhibit a promising power conversion efficiency of 21.01% with a long T80 lifetime of ≈632 h under operational conditions. This work paves the way for the further development of new dopant‐free self‐assembled HTM designs for highly efficient and stable inverted PSCs. [ABSTRACT FROM AUTHOR]

Hybrid inorganic–organic semiconductor (HIOS) interfaces are of interest for new photovoltaic devices operating above the Shockley–Queisser limit. Predicting energy band alignment at the interfaces is crucial for their design, but represents a challenging problem due to the large scales of the system, the energy precision required and a wide range of physical phenomena that occur at the interface. To tackle this problem, many‐body perturbation theory in the non‐self‐consistent GW approximation, orbital relaxation corrections for organic semiconductors, and line‐up potential method for inorganic semiconductors which allows for tractable and accurate computing of energy band alignment in crystalline van‐der‐Waals hybrid inorganic–organic semiconductor interfaces are used. In this work, crystalline tetracene physisorbed on the clean hydrogen‐passivated 1 × 2 reconstructed (100) silicon surface is studied. Using this computational approach, it is found that the energy band alignment is determined by an interplay of the mutual dynamic dielectric screening of two materials and the formation of a dipole layer due to a weak hybridization of atomic/molecular orbitals at the interface. The significant role of the exchange‐correlation effects in predicting band offsets for the hybrid inorganic–organic semiconductor interfaces is also emphasized. [ABSTRACT FROM AUTHOR]

2D materials are increasingly being investigated for their nonvolatile switching properties as a step toward downscaling of core electronic elements. Here, the interplay between electrochemically active silver (Ag) cations and layered indium selenide (InSe), a 2D metal monochalcogenide, is investigated to demonstrate a nonvolatile switching device. Detailed microscopic characterization supported with density functional theory calculations reveals cationic filamentary‐based nonvolatile switching mechanism of γ‐InSe in a crossplanar architecture. This is electrically driven by diffusion of Ag ions through the layered InSe stack. The InSe‐based memory cells exhibit a switching ratio of ≈103 and a memory retention of >105 s. This work opens new opportunities to enhance resistive switching performances of 2D materials for next‐generation information storage and brain inspired computation using active metal diffusion. [ABSTRACT FROM AUTHOR]

The integration of a functional group into dopant‐free hole‐transport materials (HTMs) to modify the perovskite|HTM interface has become a promising strategy for high‐performance and stable perovskite solar cells (PSCs). In this work, a sulfonated phenothiazine‐based HTM is reported, namely TAS, which consists of a butterfly structure with a readily synthesized N,​N‐​bis[4‐​(methylthio)​phenyl]​aniline side functional group. The interaction between TAS and perovskite via Pb–S bond induces a dipole moment that deepens the valence band of perovskite and thereby leads to enhanced open‐circuit voltage in corresponding n‐i‐p PSCs. More importantly, the functionalization of perovskite surface via Pb–S bond promotes the hole extraction reaction while suppressing the interfacial non‐radiative recombination, contributing to a 20–50% performance improvement compared to less‐ (4‐​(methylthio)​‐​N‐​[4‐​(methylthio)​phenyl]​aniline, DAS) or non‐interacting (N,N‐bis(4‐methoxyphenyl)aniline, TAO) counterparts. Consequently, TAS‐based PSCs exhibit superior device stability with a high PCE retention (>90% of the initial value) after 125 days of storage in the air. [ABSTRACT FROM AUTHOR]

Reverse Monte Carlo (RMC) simulations were performed to investigate the effectiveness of any combination of five experimentally motivated constraints on the reproduction of a test case, a ternary ab initio model. It was found that low energy structures fitting a variety of constraints commonly used in the RMC methodology could still provide an incorrect description of the chemical structural unit populations in multi-elemental systems. It is shown that the use of an elemental bond type constraint is an effective way to avoid this. © 2017 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]