In order to fulfill the complex cognitive behaviors in neuromorphic systems with reduced peripheral circuits, the reliable electronic synapses mimicked by single device that achieves diverse long-term and short-term plasticity are essential. Phase change random access memory (PCRAM) is of great potential for artificial synapses, which faces, however, difficulty to realize short-term plasticity due to the long-lasting resistance drift. This work reports the ruthenium-doped Ge₂Sb₂Te₅ (RuGST) based PCRAM, demonstrating a series of synaptic behaviors of short-term potentiation, pair-pulse facilitation, long-term depression, and short-term plasticity in the same single device. The optimized RuGST electronic synapse with the high transformation temperature of hexagonal phase >380°C, the outstanding endurance >10⁸ cycles, the low resistance drift factor of 0.092, as well as the extremely high linearity with correlation coefficients of 0.999 and 0.976 in parts of potentiation and depression. Further investigations also go insight to mechanisms of Ru doping according to thorough microstructure characterization, revealing that Ru dopant is able to enter GST lattices thus changing and stabilizing atomic arrangement of GST. This leads to the short-term plasticity realized by RuGST PCRAM. Eventually, the proposed RuGST electronic synapses performs a high accuracy of ∼94.1% in a task of image recognition of CIFAR-100 database using ResNet 101. This work promotes the development of PCRAM platforms for large-scale neuromorphic systems.

Photonic and plasmonic hybrid nanostructures are the key solution for integrated nanophotonic circuits with ultracompact size but relative low loss. However, the poor tunability and modulability of conventional waveguides makes them cumbersome for optical multiplexing. Here we make use of two-dimensional molecular crystal, α-Sb₂O₃ as a dielectric waveguide via total internal reflection, which shows polarization-sensitive modulation of the propagating beams due to its large polarization mode dispersion. Both experiments and simulations are performed to verify such concept. These Sb₂O₃ nanoflakes can be coupled with plasmonic nanowires to form nanophotonic beam splitters and routers which can be easily modulated by changing the polarization of the incidence. It thus provides a robust, exploitable and tunable platform for on-chip nanophotonics.

The rapid development of emerging technologies observed in recent years, such as artificial intelligence, machine learning, mobile internet, big data, cloud computing, and the Internet of Everything, are generating escalating demands for expanding the capacity density, and speed in next-generation optical communications. This poses a significant challenge to existing communication techniques. Within this context, the integration of near-infrared broadband, tunable, and high-gain luminescent materials into silicon optical circuits or fiber architectures to transmit and modulate light shows enormous potential for advancing next-generation communication techniques. Here, this review provides an overview of the recent breakthroughs in near-infrared luminescent epitaxial/colloidal quantum dots, and metal-active-center-doped materials for broadband optical amplifiers and tunable lasers. We also expound on efforts to enhance the bandwidth and gain of these materials-based amplifiers and lasers, exploring the challenges associate with developing ultra-broadband and high-speed optical communication systems. Additionally, the potential applications in Fifth Generation Fixed Networks, integration with 5G and 6G wireless networks, compensation for current Si electronic based CMOS for high computing capability, and the prospects of these light sources for next-generation optoelectronic devices are discussed.

Two-dimensional (2D) non-layered materials, along with their unique surface properties, offer intriguing prospects for sensing applications. Introducing mechanical degrees of freedom is expected to enrich the sensing performances of 2D non-layered devices, such as high frequency, high tunability, and large dynamic range, which could lead to new types of high performance nanosensors. Here, we demonstrate 2D non-layered nanomechanical resonant sensors based on β-In₂S₃, where the devices exhibit robust nanomechanical vibrations up to the very high frequency (VHF) band. We show that such device can operate as pressure sensor with broad range (from 10^–3 Torr to atmospheric pressure), high linearity (with a nonlinearity factor as low as 0.0071), and fast response (with an intrinsic response time less than 1 µs). We further unveil the frequency scaling law in these β-In₂S₃ nanomechanical sensors and successfully extract both the Young’s modulus and pretension for the crystal. Our work paves the way towards future wafer-scale design and integrated sensors based on 2D non-layered materials.

Halide perovskite single crystals (SCs) have attracted much attention for their application in high-performance x-ray detectors owing to their desirable properties, including low defect density, high mobility–lifetime product (µτ), and long carrier diffusion length. However, suppressing the inherent defects in perovskites and overcoming the ion migration primarily caused by these defects remains a challenge. This study proposes a facile process for dipping Cs_0.05FA_0.9MA_0.05PbI₃ SCs synthesized by a solution-based inverse temperature crystallization method into a 2-phenylethylammonium iodide (PEAI) solution to reduce the number of defects, inhibit ion migration, and increase x-ray sensitivity. Compared to conventional spin coating, this simple dipping process forms a two-dimensional PEA₂PbI₄ layer on all SC surfaces without further treatment, effectively passivating all surfaces of the inherently defective SCs and minimizing ion migration. As a result, the PEAI-treated perovskite SC-based x-ray detector achieves a record x-ray sensitivity of 1.3 × 10⁵ µC Gy_air^–1 cm^–2 with a bias voltage of 30 V at realistic clinical dose rates of 1–5 mGy s^–1 (peak potential of 110 kVp), which is 6 times more sensitive than an untreated SC-based detector and 3 orders of magnitude more sensitive than a commercial α-Se-based detector. Furthermore, the PEAI-treated-perovskite SC-based x-ray detector exhibits a low detection limit (73 nGy s^–1), improved x-ray response, and clear x-ray images by a scanning method, highlighting the effectiveness of the PEAI dipping approach for fabricating next-generation x-ray detectors.

All-solid-state batteries equipped with solid-state electrolytes (SSEs) have gained significant interest due to their enhanced safety, energy density, and longevity in comparison to traditional liquid organic electrolyte-based batteries. However, many SSEs, such as sulfides and hydrides, are highly sensitive to water, limiting their practical use. As one class of important perovskites, the Ruddlesden–Popper perovskite oxides (RPPOs), show great promise as SSEs due to their exceptional stability, particularly in terms of water resistance. In this review, the crystal structure and synthesis methods of RPPOs SSEs are first introduced in brief. Subsequently, the mechanisms of ion transportation, including oxygen anions and lithium-ions, and the relevant strategies for enhancing their ionic conductivity are described in detail. Additionally, the progress made in developing flexible RPPOs SSEs, which are critical for flexible and wearable electronic devices, has also been summarized. Furthermore, the key challenges and prospects for exploring and developing RPPOs SSEs in all-solid-state batteries are suggested. This review presents in detail the synthesis methods, the ion transportation mechanism, and strategies to enhance the room temperature ionic conductivity of RPPOs SSEs, providing valuable insights on enhancing their ionic conductivity and thus for their practical application in solid-state batteries.

Organic photovoltaics (OPVs) represent one of the most promising photovoltaic technologies owing to their high capacity to convert solar energy to electricity. With the continuous structure upgradation of photovoltaic materials, especially that of non-fullerene acceptors (NFAs), the OPV field has witnessed rapid progress with power conversion efficiency (PCE) exceeding 19%. However, it remains challenging to overcome the intrinsic trade-off between the photocurrent and photovoltage, restricting the further promotion of the OPV efficiency. In this regard, it is urgent to further tailor the structure of NFAs to broaden their absorption spectra while mitigating the energy loss of relevant devices concomitantly. Heteroatom substitution on the fused-ring π-core of NFAs is an efficient way to achieve this goal. In addition to improve the near-infrared light harvest by strengthening the intramolecular charge transfer, it can also enhance the molecular stacking via forming multiple noncovalent interactions, which is favorable for reducing the energetic disorder. Therefore, in this review we focus on the design rules of NFAs, including the polymerized NFAs, of which the core moiety is substituted by various kinds of heteroatoms. We also afford a comprehensive understanding on the structure–property–performance relationships of these NFAs. Finally, we anticipate the challenges restricting the efficiency promotion and industrial utilization of OPV, and provide potential solutions based on the further heteroatom optimization on NFA core-moiety.

Electrochemical transformation processes involving carbon, hydrogen, oxygen, nitrogen, and small-molecule chemistries represent a promising means to store renewable energy sources in the form of chemical energy. However, their widespread deployment is hindered by a lack of efficient, selective, durable, and affordable electrocatalysts. Recently, grain boundary (GB) engineering as one category of defect engineering, has emerged as a viable and powerful pathway to achieve improved electrocatalytic performances. This review presents a timely and comprehensive overview of recent advances in GB engineering for efficient electrocatalysis. The beneficial effects of introducing GBs into electrocatalysts are discussed, followed by an overview of the synthesis and characterization of GB-enriched electrocatalysts. Importantly, the latest developments in leveraging GB engineering for enhanced electrocatalysis are thoroughly examined, focusing on the electrochemical utilization cycles of carbon, hydrogen, oxygen, and nitrogen. Future research directions are proposed to further advance the understanding and application of GB engineering for improved electrocatalysis.