Inspired by the remarkably high efficiency of the human retina, neuromorphic image sensors are attracting more and more attention. As the core component for optoelectronic conversion, optoelectronic synapses are hotly pursued under the stimulus of monochromatic light, limiting the capability of full‐color imaging in one active cell. Herein, by leveraging the outstanding broadband photoresponse and distinct wavelength‐dependent temporal current evolution, a neuromorphic multicolor image sensor is demonstrated based on oxygen‐vacancy‐mediated amorphous Ga 2 O 3 (a‐Ga 2 O 3 ) thin film. Typical synaptic functions, including paired‐pulse facilitation and the learning‐relearning process, have been successfully mimicked under different light illumination. A 10×10 imaging array well identifies multicolor patterns under raster scanning of focused laser beams of 638, 520, and 405 nm, which is enabled by the combination of distinguishable photocurrent levels and memorizing/fading time of the final pictures among different wavelengths. The underlying mechanism of the visible photoresponse is further explored through scanning photocurrent microscopy measurement, suggesting the synergetic role of optical and electric fields on the dynamic behaviors of the photo‐induced carriers assisted by the V O ‐related sub‐bandgap defects. This work provides a strategy to encode the color information in the time domain, offering a potential solution to construct a compact filter‐free machine vision system in the future.

ABSTRACT Amorphous van der Waals (vdW) materials introduce atomic disorder into layered systems, providing an additional degree of freedom for tailoring optoelectronic responses and photoinduced carrier dynamics beyond the crystalline regime. Yet, atomically thin amorphous van der Waals nanosheets with reproducible device‐level properties remain largely unexplored. Here, we report an electrochemical exfoliation strategy that directly converts single‐crystal TaIrTe 4 into amorphous nanosheets with average lateral dimensions exceeding 50 µm, thickness down to 2 nm, and high ambient stability. Structural amorphization induces a metallic‐to‐semiconducting transition accompanied by bandgap opening and the formation of distributed trap states, as supported by density functional theory. Field‐effect transistors fabricated from these nanosheets exhibit ambipolar transport with on/off ratios above 103 and mobilities of ∼1.5 cm 2 V −1 s −1 , enabling sensitive electrical readout. Upon optical stimulation, the devices generate self‐powered, persistent photocurrents. Wavelength‐selective excitation between 405 nm and 638 nm produces reversible conductance potentiation and depression, realizing fully optical and bidirectional synaptic plasticity with ultralow energy consumption (< 5.65 pJ per pulse). Neuromorphic network simulations incorporating the experimentally extracted dynamics achieve 92.1% on the MNIST dataset. These results demonstrate a scalable platform for producing amorphous vdW nanosheets and show that crystalline‐to‐amorphous conversion enables light‐programmable signal processing and energy‐efficient intelligent hardware.

ABSTRACT Two‐dimensional transition‐metal dichalcogenides, especially molybdenum disulfide (MoS 2 ), have emerged as a promising channel material for next‐generation electronic and optoelectronic devices due to their atomic thickness and excellent electrostatic integrity. However, the performance of MoS 2 devices on conventional planar silicon (Si) substrates often suffer from limited performance caused by carrier scattering, insufficient electrostatic control, and self‐heating. In this work, we demonstrate a vertical heterostructure of MoS 2 with a Si nanomesh substrate via a scalable process. The Si nanomesh is fabricated through nanosphere lithography and the MoS 2 /Si heterostructure is fabricated by conformal deposition of MoS 2 using reactive magnetron sputtering and atmospheric‐pressure sulfurization. Photodetector based on the nanostructured MoS 2 /Si heterojunction exhibit enhanced electrical conductivity and higher photocurrent compared to planar MoS 2 /Si devices and can be operated without external power. Photocurrent mappings further reveal that the MoS 2 /Si heterojunction region primarily governs the photoresponse, functioning in a photovoltaic mode at zero bias and shifting to an avalanche‐assisted regime under reverse bias. A peak responsivity of 205 mA W −1 is achieved with rise and decay times of 150 and 100 ms, respectively. These results demonstrate that the integration of MoS 2 /Si nanomesh platform offers a CMOS‐compatible and scalable pathway for high‐performance 2D semiconductor electronics and optoelectronics.

Amorphous van der Waals (vdW) materials introduce atomic disorder into layered systems, providing an additional degree of freedom for tailoring optoelectronic responses and photoinduced carrier dynamics beyond the crystalline regime. Yet, atomically thin amorphous van der Waals nanosheets with reproducible device-level properties remain largely unexplored. Here, we report an electrochemical exfoliation strategy that directly converts single-crystal TaIrTe4 into amorphous nanosheets with average lateral dimensions exceeding 50 µm, thickness down to 2 nm, and high ambient stability. Structural amorphization induces a metallic-to-semiconducting transition accompanied by bandgap opening and the formation of distributed trap states, as supported by density functional theory. Field-effect transistors fabricated from these nanosheets exhibit ambipolar transport with on/off ratios above 103 and mobilities of ∼1.5 cm2 V-1 s-1, enabling sensitive electrical readout. Upon optical stimulation, the devices generate self-powered, persistent photocurrents. Wavelength-selective excitation between 405 nm and 638 nm produces reversible conductance potentiation and depression, realizing fully optical and bidirectional synaptic plasticity with ultralow energy consumption (< 5.65 pJ per pulse). Neuromorphic network simulations incorporating the experimentally extracted dynamics achieve 92.1% on the MNIST dataset. These results demonstrate a scalable platform for producing amorphous vdW nanosheets and show that crystalline-to-amorphous conversion enables light-programmable signal processing and energy-efficient intelligent hardware.

The increasing complexity of intelligent sensing environments, driven by the growth of Internet of Things technologies, has created a strong demand for neuromorphic systems capable of real-time, low-power multisensory perception. Traditional sensory architectures, constrained by single-modal processing and centralized computing, struggle to meet the requirements of diverse and dynamic input conditions. Multisensory neuromorphic devices offer a promising solution by mimicking the distributed, event-driven processing of biological systems. Recent efforts have explored synaptic devices and material systems that respond to various input modalities, including visual, tactile, thermal, and chemical stimuli. However, challenges remain in signal conversion, encoding compatibility, and the fusion of heterogeneous inputs without loss of unisensory information. This review provides a comprehensive overview of the physical mechanisms, device behaviors, and integration strategies that underpin signal processing in neuromorphic hardware. We highlight synaptic mechanisms conducive to cross-modal interaction, analyze representative signal fusion approaches at the device level, and discuss future directions for constructing efficient, scalable, and biologically inspired multisensory neuromorphic systems.

With the rapid advancement of the information era, the demand for device integration and intelligent sensing has grown significantly. Traditional three-dimensional (3D) materials are constrained by lattice mismatch and interfacial defects, and their limited functionalities often require bulky auxiliary components. In contrast, the rich family of two-dimensional (2D) materials eliminates lattice-matching constraints and offers unique light-matter interactions, paving the way for compact and novel intelligent sensing technologies. However, large-area fabrication and precise layer alignment in all-2D systems remain major challenges that hinder device scalability. Given that the performance and manufacturing capabilities of 2D materials cannot replace traditional semiconductors (such as Si), they are more likely to be heterogeneously integrated with conventional 3D semiconductors. 2D/3D heterojunctions combine the distinctive optoelectronic properties of 2D materials with the mature electronic functionalities of 3D semiconductors. In this work, we present recent advances in 2D/3D heterojunction photodetectors, with a particular emphasis on the underlying physical mechanisms, including band structure design, interface optimization, external-field coupling, and novel topological configurations. Meanwhile, we also explore emerging opportunities for CMOS-compatible and intelligent sensing optoelectronic systems. Finally, the challenges and future research directions toward the integrated development of 2D/3D heterojunctions are discussed.

ABSTRACT Machine vision systems in real‐world applications require devices capable of adapting to multiple operational modes, including high‐sensitivity photodetection, neuromorphic synaptic behavior, and optical memory. However, integrating these distinct optoelectronic functionalities into a single device presents a challenge due to their conflicting requirements for photoresponse time and retention. Here, a gate‐programmable multifunctional transistor based on a MoS2/MAPbBr3 van der Waals (vdW) heterostructure is fabricated. By using the gate field to tune the interfacial electric field and trapping/release kinetics associated with shallow‐ and deep‐level states, the device can be programmed to operate as a photodetector, synaptic transistor, and gate‐bias‐assisted multilevel optical memory. Under a positive gate voltage (VG), a pronounced photogating effect enables photodetection with responsivity (R) of ∼2397 A/W. At VG = –20 V, the device switches to synaptic mode. At a more negative gate bias, the device enters a gate‐bias‐assisted optical‐memory mode under sustained gate bias. To illustrate the utility of this programmable multifunctionality, frequency‐encoded image recognition is demonstrated with 96.4% accuracy. In addition, a device‐enabled reservoir‐computing (RC) scheme with software‐assisted readout improves classification accuracy by ~20% through deep delay‐based processing. This work demonstrates a multimodal transistor architecture that integrates multiple optoelectronic functions in a single device and suggests a compact hardware route toward adaptive in‐sensor optical information processing.

Interface engineering via pre-engineered black phosphorus quantum dots leads to efficiency improvement from 13.8% to 17.1% for planar HTL-free C-PSCs.

Abstract Intelligent mid-infrared (MIR) imaging integrates in-sensor preprocessing of thermal information, thereby reducing data redundancy and improving target-recognition robustness under low-visibility conditions. However, unlike in the visible regime, photoconductive programmability in the MIR typically relies on narrow-bandgap materials, which inherently limit stable and reconfigurable operation. Here, we report a programmable photothermoelectric (PTE) detector based on a suspended nanometer-thick SrTiO3 membrane. Dimensional scaling of the thermoelectric channel enhances sensitivity and enables a response time of ∼10 μs, over 104 times faster than bulk SrTiO3. Through dual-gate electrostatic modulation of the Seebeck profile, the device exhibits bidirectionally tunable photothermoelectric responsivity up to 50 V W−1 and supports 40 experimentally observed programmable response states. By leveraging a 3 × 3 programmable device array with device-to-device consistent gate-programmable photoresponse and reproducible polarity switching, a recognition accuracy of 83% is achieved under visually degraded conditions. Furthermore, the programmable array enables attention-guided thermal image weighting by enhancing target thermal signatures while suppressing background interference. These results demonstrate the dimensional scaling of perovskite oxides as an effective route toward adaptive, low-power machine vision and neuromorphic infrared electronics.

Abstract Recent advancements in integrated two-dimensional (2D) nonlinear optical (NLO) materials open new avenues for photonic technologies. This structure of 2D materials leads to strong light–matter interaction, high carrier density, quantum confinement effect and tunable bandgap, which contribute to their high NLO coefficients, ease tuning of their NLO properties, and ease of integration with micro-optoelectronic devices. This review focuses on recent advances in 2D NLO materials for integrated optical platforms. We first discuss the various strategies for integrating 2D NLO materials with photonic structures such as waveguides, optical fibers, microcavities, and metasurfaces. Next, we highlight the NLO phenomena exhibited by these integrated systems, including harmonic generation, multiphoton processes, and nonlinear refraction and absorption. Finally, we highlight emerging applications in areas such as nonlinear light sources, ultrafast pulse generation, optical frequency combs, photodetectors, terahertz generation, and optical computing. By highlighting recent breakthroughs, this review aims to provide a roadmap for advancing integrated 2D materials toward high-performance photonic technologies.

Layered van der Waals materials have attracted increasing interest as a nonlinear optical component for advanced laser systems. Here, we demonstrate layered NbOCl2 as a nonlinear platform enabling ultrafast and excitable fiber laser operation in the telecommunication band. High-quality NbOCl2 crystals synthesized by chemical vapor transport can be exfoliated into few-layer flakes exhibiting saturable absorption with low saturation intensity. By incorporating NbOCl2 into an erbium-doped fiber laser, stable self-starting mode-locked operation is achieved at a threshold pump power of 77 mW. The laser generates pulses with pulses centered at 1593 nm, with a 3 dB bandwidth of 2.5 nm, a repetition rate of 4.5 MHz, a signal-to-noise ratio exceeding 60 dB, and maintains stable operation over 24 h. Beyond mode-locked and Q-switched regimes, the same laser system can be operated in an excitable regime, where isolated optical spikes are generated in response to external perturbations, exhibiting threshold-like and all-or-none spiking behavior. These results highlight the versatility of NbOCl2 as a nonlinear optical platform for ultrafast and excitable fiber lasers and indicate its potential relevance for spike-based photonic neuromorphic systems.

Transparent flexible field-effect transistors (FETs) are increasingly desired for cutting-edge electronics, but the performance of flexible two-dimensional (2D) FETs still lags behind traditional rigid 2D devices. This study addresses this issue by introducing lithographically defined poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) electrodes to fabricate high-performance 2D transistors via a transfer method. Both flexible MoS₂ FET and its rigid counterpart demonstrated impressive electron mobility values of 154 ± 20.4 cm² V⁻¹ s⁻¹ and 155 ± 15.9 cm² V⁻¹ s⁻¹ , respectively. The PEDOT:PSS/MoS₂ interface interaction was meticulously characterized and computationally analyzed to elucidate the operational mechanisms. A fully transparent flexible 2D transistor with 71 % transmittance over the visible spectrum and robust FET performance under mechanical bending was also demonstrated. This work highlights the significant potential of integrating organic polymer electrodes with advanced 2D materials for novel high-performance device applications.

Interlayer insertion has emerged as one of the key strategies for contact engineering in two-dimensional (2D) field-effect transistors (FETs). However, conventional interlayers such as hexagonal boron nitride (hBN) have limitations in contact performance and face challenges in achieving low-thermal-budget large-area fabrication. In this work, we explore the functionalization of printed ultrathin gallium oxide (GaOx) films as tunneling contact layers in 2D transistors. Leveraging self-limiting oxidation of liquid gallium, we fabricate nanometer-thick GaOx films (3.6 nm) that possess shallow defect states arising from oxygen vacancies, thereby narrowing the tunneling barrier width. When integrated as a tunneling layer in multilayer WS2 field-effect transistors, the GaOx film significantly enhances device performance, achieving a record electron mobility of 296 cm(2)& centerdot;V-1 & centerdot;s(-1), an ultra-low contact resistance of 2.38 k Omega & centerdot;mu m, and a minimal contact barrier height of 3.7 meV. Distinct from conventional insulating tunneling dielectrics, the observed performance enhancement originates from a hybrid tunneling mechanism within GaOx, which is activated under the synergy of multiple electric fields and temperatures. Oxygen vacancies act as dynamic conduction channels that mediate composite tunneling pathways combining defect-assisted, direct, and Fowler-Nordheim tunneling, thus enabling efficient carrier injection across the interface. In addition, the low-temperature printing method also enables van der Waals integration in scalable fabrication without the Fermi pinning effect. This study not only demonstrates the new functional application of printed GaOx films and clarifies the role of their oxygen vacancies in the tunneling mechanism but also proposes a novel, scalable strategy for optimizing contact engineering in low-dimensional electronic devices.

Two-dimensional transition-metal dichalcogenides, especially molybdenum disulfide (MoS2), have emerged as a promising channel material for next-generation electronic and optoelectronic devices due to their atomic thickness and excellent electrostatic integrity. However, the performance of MoS2 devices on conventional planar silicon (Si) substrates often suffer from limited performance caused by carrier scattering, insufficient electrostatic control, and self-heating. In this work, we demonstrate a vertical heterostructure of MoS2 with a Si nanomesh substrate via a scalable process. The Si nanomesh is fabricated through nanosphere lithography and the MoS2/Si heterostructure is fabricated by conformal deposition of MoS2 using reactive magnetron sputtering and atmospheric-pressure sulfurization. Photodetector based on the nanostructured MoS2/Si heterojunction exhibit enhanced electrical conductivity and higher photocurrent compared to planar MoS2/Si devices and can be operated without external power. Photocurrent mappings further reveal that the MoS2/Si heterojunction region primarily governs the photoresponse, functioning in a photovoltaic mode at zero bias and shifting to an avalanche-assisted regime under reverse bias. A peak responsivity of 205 mA W-1 is achieved with rise and decay times of 150 and 100 ms, respectively. These results demonstrate that the integration of MoS2/Si nanomesh platform offers a CMOS-compatible and scalable pathway for high-performance 2D semiconductor electronics and optoelectronics.

Inspired by the remarkably high efficiency of the human retina, neuromorphic image sensors are attracting more and more attention. As the core component for optoelectronic conversion, optoelectronic synapses are hotly pursued under the stimulus of monochromatic light, limiting the capability of full-color imaging in one active cell. Herein, by leveraging the outstanding broadband photoresponse and distinct wavelength-dependent temporal current evolution, a neuromorphic multicolor image sensor is demonstrated based on oxygen-vacancy-mediated amorphous Ga2O3 (a-Ga2O3) thin film. Typical synaptic functions, including paired-pulse facilitation and the learning-relearning process, have been successfully mimicked under different light illumination. A 10x10 imaging array well identifies multicolor patterns under raster scanning of focused laser beams of 638, 520, and 405 nm, which is enabled by the combination of distinguishable photocurrent levels and memorizing/fading time of the final pictures among different wavelengths. The underlying mechanism of the visible photoresponse is further explored through scanning photocurrent microscopy measurement, suggesting the synergetic role of optical and electric fields on the dynamic behaviors of the photo-induced carriers assisted by the VO-related sub-bandgap defects. This work provides a strategy to encode the color information in the time domain, offering a potential solution to construct a compact filter-free machine vision system in the future.

Two-dimensional van der Waals layered materials combining strong second-order nonlinearity with electrical tunability offer attractive opportunities for integrated nonlinear photonics. Among them, layered III-VI semiconductors such as GaSe and InSe exhibit robust second-order nonlinear responses independent of odd-even layer-number parity. Here, we investigate the thickness-dependent second-harmonic generation (SHG) and electric-field modulation in layered GaSe and InSe. The SHG intensity shows a nonlinear scaling with thickness, enabling quantitative extraction of the effective second-order nonlinear susceptibility, reaching approximately 28.1 pm V-1 for GaSe and 31.1 pm V-1 for InSe. Over a thickness range of 10-120 nm, phase-matching effects are minimal while the susceptibility shows a slight decrease with increasing thickness. Electrically tunable SHG with a modulation depth exceeding 20% is demonstrated in field-effect transistor devices, and reversible electro-optic modulation of evanescent-field-coupled optical transmission is achieved in fiber-integrated structures. These results highlight the potential of layered III-VI semiconductors for electrically tunable nonlinear and electro-optic photonic technologies.

ABSTRACT Layered van der Waals materials have attracted increasing interest as a nonlinear optical component for advanced laser systems. Here, we demonstrate layered NbOCl 2 as a nonlinear platform enabling ultrafast and excitable fiber laser operation in the telecommunication band. High‐quality NbOCl 2 crystals synthesized by chemical vapor transport can be exfoliated into few‐layer flakes exhibiting saturable absorption with low saturation intensity. By incorporating NbOCl 2 into an erbium‐doped fiber laser, stable self‐starting mode‐locked operation is achieved at a threshold pump power of 77 mW. The laser generates pulses with pulses centered at 1593 nm, with a 3 dB bandwidth of 2.5 nm, a repetition rate of 4.5 MHz, a signal‐to‐noise ratio exceeding 60 dB, and maintains stable operation over 24 h. Beyond mode‐locked and Q‐switched regimes, the same laser system can be operated in an excitable regime, where isolated optical spikes are generated in response to external perturbations, exhibiting threshold‐like and all‐or‐none spiking behavior. These results highlight the versatility of NbOCl 2 as a nonlinear optical platform for ultrafast and excitable fiber lasers and indicate its potential relevance for spike‐based photonic neuromorphic systems.

Abstract Interlayer insertion has emerged as one of the key strategies for contact engineering in two-dimensional (2D) field-effect transistors (FETs). However, conventional interlayers such as hexagonal boron nitride (hBN) have limitations in contact performance and face challenges in achieving low-thermal-budget large-area fabrication. In this work, we explore the functionalization of printed ultrathin gallium oxide (GaO x ) films as tunneling contact layers in 2D transistors. Leveraging self-limiting oxidation of liquid gallium, we fabricate nanometer-thick GaO x films (3.6 nm) that possess shallow defect states arising from oxygen vacancies, thereby narrowing the tunneling barrier width. When integrated as a tunneling layer in multilayer WS 2 field-effect transistors, the GaO x film significantly enhances device performance, achieving a record electron mobility of 296 cm 2 ·V −1 ·s −1 , an ultra-low contact resistance of 2.38 kΩ·μm, and a minimal contact barrier height of 3.7 meV. Distinct from conventional insulating tunneling dielectrics, the observed performance enhancement originates from a hybrid tunneling mechanism within GaO x , which is activated under the synergy of multiple electric fields and temperatures. Oxygen vacancies act as dynamic conduction channels that mediate composite tunneling pathways combining defect-assisted, direct, and Fowler–Nordheim tunneling, thus enabling efficient carrier injection across the interface. In addition, the low-temperature printing method also enables van der Waals integration in scalable fabrication without the Fermi pinning effect. This study not only demonstrates the new functional application of printed GaO x films and clarifies the role of their oxygen vacancies in the tunneling mechanism but also proposes a novel, scalable strategy for optimizing contact engineering in low-dimensional electronic devices.

Changing it-bridge in D-it-A type polymer from thiophene to thieno[3,2-b]thiophene (TT) is an effective molecular engineering to modulate the optoelectronic properties of polymers. However, for two different types of electron acceptors, small molecule and polymer, the specific effects of it-bridge engineering have not yet been studied. Herein, two benzotriazole (BTA)-based donor polymers J52-F and PE3, are used to investigate the effect in the varying electron acceptors: small molecule acceptor Y6 and the polymer acceptor N2200. PE3 shows superior molecular compatibility with Y6 rather than N2200, while in the J52 system, it's the opposite. As a result, J52-F: N2200 and PE3: Y6 blends give rise to interpenetrating network morphology with a better domain size than their counterparts, enhancing charge transport and suppressing charge recombination. Compared with J52-F: N2200, PE3:N2200 exhibits increased radiative recombination loss due to the poor energy disorder, producing a similar open-circuit voltage (VOC) with J52:N2200. In the Y6 system, PE3 produces lower radiative and non-radiative energy loss than J52-F, leading to a higher VOC. Finally, the PE3:Y6 achieves the highest PCE of 16.63 %, obviously higher than the J52-F: Y6 (PCE = 12.75 %). Differently, in the N2200-based all-polymer solar cells, J52-F exhibits a better PCE of 8.99 % than PE3 (PCE = 3.75 %). These data demonstrate that introducing TT bridge is a prospective way of constructing high-efficiency Y6-based photovoltaic devices due to the superior molecular compatibility.

This review provides a comprehensive overview of the molecular engineering techniques used to control polarity in two-dimensional materials and their applications in optoelectronic devices.