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2D Ruddlesden─Popper (RP) halide perovskites are attracting increasing research interest due to their enhanced stability compared to 3D perovskites. However, the quantum confinement effect of bulk organic spacers hinders the separation and transport of photo‐generated carriers. Here, a multiple aromatic ring spacer, 3‐benzothiophene methylammonium (BTMA), is developed for a new 2D RP perovskite. The BTMA spacer is demonstrated, with a significant dipole moment, can impair the influence of the quantum confinement effect, and the presence of S atoms or thiophene is favorable for enhancing the interaction between organic spacers and inorganic sheets, improving the stability of perovskites. The perovskite photodetector with BTMA as spacers displays higher device performance than the control sample with 1‐naphthalene methylammonium (NMA) as spacers. Importantly, the outstanding stability of BTMA‐based perovskite films and devices is also confirmed under moisture, heat, and illumination conditions. Combining the asymmetric coplanar nanogap electrode architecture, the photodetectors' enhanced responsivity, detectivity, and external quantum efficiency of 314 A W−1, 3.4 × 1013 Jones, and 865%, respectively, are demonstrated. Importantly, the nanogap photodetectors display promising self‐power characteristics, which makes them attractive for numerous energy‐efficient applications. The work highlights a new route toward developing high‐performance 2D RP perovskite‐based photodetectors with excellent long‐term stability. [ABSTRACT FROM AUTHOR]

Zinc (Zn) has arisen as a significant suppressor of vacancy formation in halide perovskites, establishing its pivotal role in defect engineering for these materials. Herein, the Zn‐catalyzed vapor‐liquid‐solid (VLS) route is reported to render black‐phase CsPbI3 nanowires (NWs) operationally stable at room temperature. Based on first‐principle calculations, the doped Zn2+ can not only lead to the partial crystal lattice distortion but also reduce the formation energy (absolute value) from the black phase to the yellow phase, improving the stability of the desired black‐phase CsPbI3 NWs. A series of contrast tests further confirm the stabilization effect of the Zn‐doped strategy. Besides, the polarization‐sensitive characteristics of black‐phase CsPbI3 NWs are revealed. This work highlights the importance of phase stabilization engineering for CsPbI3 NWs and their potential applications in anisotropic optoelectronics. [ABSTRACT FROM AUTHOR]

The visual system, one of the most crucial units of the human perception system, combines the functions of multi‐wavelength signal detection and data processing. Herein, the large‐scale artificial synaptic device arrays based on the organic molecule‐nanowire heterojunctions with tunable photoconductivity are proposed and demonstrated. The organic thin films of p‐type 2,7‐dioctyl[1]benzothieno[3,2‐b][1] benzothiophene (C8‐BTBT) or n‐type phenyl‐C61‐butyric acid methyl ester (PC61BM) are used to wrap the InGaAs nanowire parallel arrays to configure two different type‐I heterojunctions, respectively. Due to the difference in carrier injection, persistent negative photoconductivity (NPC) or positive photoconductivity (PPC) are achieved in these heterojunctions. The irradiation with different wavelengths (solar‐blind to visible ranges) can stimulate the heterojunction devices, effectively mimicking the synaptic behaviors with two different photoconductivities. The long‐term and multi‐state light memory are also realized through synergistic photoelectric modulation. Notably, the arrays with different photoconductivities are adopted to build the hardware kernel for the visual system. Due to the tunable photoconductivity and response to multiple wavelengths, the recognition rate of neural networks can reach 100% with lower complexity and power consumption. Evidently, these photosynaptic devices are illustrated with retina‐like behaviors and capabilities for large‐area integration, which reveals their promising potential for artificial visual systems. [ABSTRACT FROM AUTHOR]

Controllable self‐catalyzed growth of semiconductor nanowires (NWs) is of great importance, particularly to avoid impurities coming from foreign catalysts to deteriorate the NW properties. Although this catalyst‐free NW growth has many obvious advantages, there are very limited works focused on all‐inorganic CsPbBr3 perovskite NWs, which is one of the recent champion materials for electronics and optoelectronics. Here, a direct self‐catalyzed synthesis of freestanding CsPbBr3 NWs via vapor–liquid–solid growth mechanism by chemical vapor deposition is developed. Notably, mainipulation of the substrate surface roughness is the key enabling parameter for the self‐catalyzed NW growth here. It is revealed that the surface energy of substrates, modulated by its surface roughness, is found to effectively mediate the self‐catalytic growth of CsPbBr3 NWs. When configured into photodetectors, the intrinsic p‐type CsPbBr3 NWs exhibit good optoelectronic performance with a photoresponivity of ≈2000 A W−1, a detectivity of ≈2.57 × 1012 Jones, and a fast response down to 362 µs. All these results evidently indicate the technological potential of this self‐catalyzed synthesizing route for other high‐quality all‐inorganic perovskite NWs. [ABSTRACT FROM AUTHOR]

More details can be found in article number 2200727 by Johnny C. Ho and co-workers. The unique charge transport pathways along the axial direction hold great potential in information technology. B Phototransistor Devices b Phototransistor devices based on individual single cubic phase CsPbBr SB 3 sb perovskite nanowires are fabricated and thoroughly studied. [Extracted from the article]

Dual-layer and tri-layer broadband antireflective (AR) films with excellent transmittance were successfully fabricated using base-/acid-catalyzed mixed sols and propylene oxide (PO) modified silica sols. The sols and films were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), transmission electron microscope (TEM), and scanning transmission electron microscope (STEM). FTIR and TEM results suggest that the PO molecules were covalently bonded to the silica particles and the bridge structure existing in PO modified silica sol is responsible for the low density of the top layer. The density ratio between different layers was measured by cross-sectional STEM, and the results are 1.69:1 and 2.1:1.7:1 from bottom-layer to top-layer for dual-layer and tri-layer films, respectively. The dual-layer film demonstrates good stability with 99.8% at the central wavelength of 351 nm and nearly 99.5% at the central wavelength of 1053 nm in laser system, and for the tri-layer AR film, the maximum transmittance reached nearly 100% at both the central wavelengths of 527 and 1053 nm. [ABSTRACT FROM AUTHOR]

Atomically 2D layered ferroelectric semiconductors, in which the polarization switching process occurs within the channel material itself, offer a new material platform that can drive electronic components toward structural simplification and high-density integration. Here, a room-temperature 2D layered ferroelectric semiconductor, bismuth oxychalcogenides (Bi 2 O 2 Se), is investigated with a thickness down to 7.3 nm (≈12 layers) and piezoelectric coefficient (d 33 ) of 4.4 ± 0.1 pm V -1 . The random orientations and electrically dependent polarization of the dipoles in Bi 2 O 2 Se are separately uncovered owing to the structural symmetry-breaking at room temperature. Specifically, the interplay between ferroelectricity and semiconducting characteristics of Bi 2 O 2 Se is explored on device-level operation, revealing the hysteresis behavior and memory window (MW) formation. Leveraging the ferroelectric polarization originating from Bi 2 O 2 Se, the fabricated device exhibits "smart" photoresponse tunability and excellent electronic characteristics, e.g., a high on/off current ratio > 10 4 and a large MW to the sweeping range of 47% at V GS  = ±5 V. These results demonstrate the synergistic combination of ferroelectricity with semiconducting characteristics in Bi 2 O 2 Se, laying the foundation for integrating sensing, logic, and memory functions into a single material system that can overcome the bottlenecks in von Neumann architecture., (© 2023 Wiley-VCH GmbH.)

Converting vapor precursors to solid nanostructures via a liquid noble-metal seed is a common vapor deposition principle. However, such a noble-metal-seeded process is excluded from the crystalline halide perovskite synthesis, mainly hindered by the growth mechanism shortness. Herein, powered by a spontaneous exothermic nucleation process (Δ H < 0), the Au-seeded CsPbI 3 nanowires (NWs) growth is realized based on a vapor-liquid-solid (VLS) growth mode. It is energetically favored that the Au seeds are reacted with a Pb vapor precursor to form molten Au-Pb droplets at temperatures down to 212 °C, further triggering the low-temperature VLS growth of CsPbI 3 NWs. More importantly, this Au-seeded process reduces in-bandgap trap states and consequently avoids Shockley-Read-Hall recombination, contributing to outstanding photodetector performances. Our work extends the powerful Au-seeded VLS growth mode to the emerging halide perovskites, which will facilitate their nanostructures with tailored material properties.

The incapability of modulating the photoresponse of assembled heterostructure devices has remained a challenge for the development of optoelectronics with multifunctionality. Here, a gate-tunable and anti-ambipolar phototransistor is reported based on 1D GaAsSb nanowire/2D MoS 2 nanoflake mixed-dimensional van der Waals heterojunctions. The resulting heterojunction shows apparently asymmetric control over the anti-ambipolar transfer characteristics, possessing potential to implement electronic functions in logic circuits. Meanwhile, such an anti-ambipolar device allows the synchronous adjustment of band slope and depletion regions by gating in both components, thereby giving rise to the gate-tunability of the photoresponse. Coupled with the synergistic effect of the materials in different dimensionality, the hybrid heterojunction can be readily modulated by the external gate to achieve a high-performance photodetector exhibiting a large on/off current ratio of 4 × 10 4 , fast response of 50 μs, and high detectivity of 1.64 × 10 11 Jones. Due to the formation of type-II band alignment and strong interfacial coupling, a prominent photovoltaic response is explored in the heterojunction as well. Finally, a visible image sensor based on this hybrid device is demonstrated with good imaging capability, suggesting the promising application prospect in future optoelectronic systems.