Bionic visual-audio photodetectors with in-sensor perception and preprocessing

Spatially resolved optoelectronic puddles of WTe2-2D Te heterostructure

Two-dimensional (2D) semiconductors have attracted significant scientific interest because of their optical properties. Their applications in optoelectronic devices can be further expanded by combining them to form heterostructures. We characterized a WTe2-2D Te heterostructure through local probing of the photocurrent with respect to the magnitude, phase, and position. Photocurrent generation within the device is divided into distinct regions: photo-thermoelectric effects occur solely at the 2D Te-Au junction area, PV-dominant effects at the 2D-WTe2 interface, and thermoelectric-to-photovoltaic crossover effects at the WTe2-2D Te overlap area. These different photocurrents cannot be fused into a single domain because each area is governed by different generation mechanisms, which depend on the location of the device. The power dependence of each photocurrent type also varies within the device. Our results indicate that careful material selection and device structure design, based on the electronic, optical, and thermal properties of the channel materials, are essential to avoid forming different optoelectronic puddles that could counteract each other within a single device.

Wavelength-Controlled Triple-Mode Photoconductance-Polarity-Switching Field Effect Transistor for Secure Time-Variable Encrypted Optical Communication

The controllable polarity switch between positive photoconductance (PPC) and negative photoconductance (NPC) in a photodetector is essential for the realization of versatile, innovative applications. Incorporating polarity-switching photoconductance with other response states, yet still posing challenges, allows for encoding multidimensional distinguishable optical information within a single device, which holds great potential for broadening application scope. Herein, three wavelength-controlled photoresponse modes are present in MoS2-based field effect transistor with lightly doped Si substrate by combining positive/negative photocurrent polarities with slow/fast response speeds. Specifically, a slow PPC response at 520 nm, along with fast bipolar infrared responses (NPC at 980 nm, PPC at 1310 nm), is integrated within a single MoS2 device. The opposite sub-bandgap infrared photoresponses are ascribed to the synergism of the bolometric effect and interfacial photogating, influenced by electrons photogenerated in Si. Based on the triple polarity-switching characteristic of the MoS2 device, the triple-channel real-time secure optical communication system with time-variable encryption algorithms is demonstrated, exponentially increasing the difficulty of brute-force cracking by synchronizing the time-variable key channel with two information channels. This work not only enhances the understanding of sub-bandgap photoresponse mechanisms in 2D material photodetectors but also offers promising avenues for the development of optoelectronics-assisted wireless communication technologies.

Tunable Bipolar Photothermoelectric Response from Mott Activation for In-Sensor Image Preprocessing

In-sensor image preprocessing, a subset of edge computing, offers a solution to mitigate frequent analog-digital conversions and the von Neumann bottleneck in conventional digital hardware. However, an efficient in-sensor device array with large-scale integration capability for high-density and low-power sensory processing is still lacking and highly desirable. This work introduces an adjustable broadband photothermoelectric detector based on a phase-change vanadium dioxide thin-film transistor. This transistor employs a vanadium dioxide/gallium nitride three-terminal structure with a gate-tunable phase transition at the gate-source junctions. This design allows for modulable photothermoelectric responsivities and alteration of the short-circuit photocurrent's polarities. The devices exhibit linear gate dependence for the broadband photoresponse and linear light-intensity dependence for both positive and negative photoresponsivities. The device's energy consumption is as low as 8 pJ per spike, which is one order of magnitude lower than that of previous Mott materials-based in-sensor preprocessing devices. A wafer-scale bipolar phototransistor array has also been fabricated by standard micro-/nano-fabrication techniques, exhibiting excellent stability and endurance (over 5000 cycles). More importantly, an integrated in-sensor convolutional network is successfully designed for simultaneous broadband image classification, medical image denoising, and retinal vessel segmentation, delivering exceptional performance and paving the way for future smart edge sensors.

High-Performance Self-Powered Photodetector Enabled by Te-Doped GeH Nanostructures Engineering

Two-dimensional (2D) Xenes, including graphene where X represents C, Si, Ge, and Te, represent a groundbreaking class of materials renowned for their extraordinary electrical transport properties, robust photoresponse, and Quantum Spin Hall effects. With the growing interest in 2D materials, research on germanene-based systems remains relatively underexplored despite their potential for tailored optoelectronic functionalities. Herein, we demonstrate a facile and rapid chemical synthesis of tellurium-doped germanene hydride (Te-GeH) nanostructures (NSs), achieving precise atomic-scale control. The 2D Te-GeH NSs exhibit a broadband optical absorption spanning ultraviolet (UV) to visible light (VIS), which is a critical feature for multifunctional photodetection. Leveraging this property, we engineer photoelectrochemical (PEC) photodetectors via a simple drop-casting technique. The devices deliver excellent performance, including a high responsivity of 708.5 µA/W, ultrafast response speeds (92 ms rise, 526 ms decay), and a wide operational bandwidth. Remarkably, the detectors operate efficiently at zero-bias voltage, outperforming most existing 2D-material-based PEC systems, and function as self-powered broadband photodetectors. This work not only advances the understanding of germanene derivatives but also unlocks their potential for next-generation optoelectronics, such as energy-efficient sensors and adaptive optical networks.

Construction and Multifunctional Photonic Applications of Light Absorption-Enhanced Silicon-Based Schottky Coupled Structures

To expand the detection capabilities of silicon (Si)-based photodetector and address key scientific challenges such as low light absorption efficiency and short carrier lifetime in Si-based graphene photodetector. This work introduces a novel Si-based Schottky coupled structure by in situ growth of 3D-graphene and molybdenum disulfide quantum dots (MoS2 QDs) on Si substrates using chemical vapor deposition (CVD) and plasma-enhanced chemical vapor deposition (PECVD) techniques. The findings validate the "dual-enhanced absorption" effect, enhancing the understanding of the mechanisms that improve optoelectronic performance. The synergistic effect of 3D-graphene's natural nano-resonant cavity and MoS2 QDs enhances light absorption efficiency and extends carrier lifetime. Introducing MoS2 QDs broadens and intensifies the built-in electric field, promoting the separation of photogenerated electrons and holes. The photodetector exhibits a wideband light response in the wavelength range of 380-2200 nm. It stably outputs photocurrent under high-frequency (1 kHz) modulated laser (2200 nm), with a responsivity (R) of 40 mA W-1 and detectivity (D*) of 1.15 × 109 Jones. Photodetectors show the ability to process and encrypt complex binary signals and achieve versatility in "AND" gate and "OR" gate logic operations, as well as image sensing (240 × 200 pixels).

All-Optical Modulation Photodetectors Based on the CdS/Graphene/Ge Sandwich Structures for Integrated Sensing-Computing

In this manuscript, an all-optical modulation photodetector based on a CdS/graphene/Ge sandwich structure is designed. In the presence of the modulation (near-infrared) light, the Fermi level of the graphene channel shifts, allowing for the tuning of the visible light response speed as well as achieving a broad responsivity range from negative (-3376 A/W) to positive (3584 A/W) response. Based on this, logical operations are performed by adjusting the power of the modulation light superimposed with the signal light. This facilitates more covert, all-optical, high-speed encrypted communication. The ultrahigh tunability and nearly symmetric positive and negative photoconductivity of all-optical modulation photodetectors significantly enhance the computational capacity of neuromorphic hardware. The proposed device exhibits substantial advantages in applications requiring high fault tolerance for integrated sensing-computing （ISC） and high-resolution motion object recognition, providing insights for the development of next-generation high-bandwidth, low-power-consumption ISC devices.

Self-Assembled Subwavelength Nanophotonic Structures for Spatial Object Localization and Tracking

Subwavelength resonant nanostructures have facilitated strong light-matter interactions and tunable degrees of freedom of light, such as spectrum, polarization, and direction, thus boosting photonic applications toward light emission, manipulation, and detection. For photodetection, resonant nanostructures have enabled emerging technologies, such as light detection and ranging, spectrometers, and polarimeters, within an ultracompact footprint. However, resonant nanophotonics usually relies on nanofabrication technology, which suffers from the trade-offs between precision and scalability. Here, we first realize the self-assembly of subwavelength resonant nanostructures of metal-halide perovskites for spatial object localization and tracking. By steering crystallization along capillary corner bridges localized at edges, we achieve single crystallinity, subwavelength size, and resonant coupling between perovskite nanowires, thus leading to an angle-resolved photodetector with an angular resolution of 0.523°. Furthermore, we integrate multiple pairs of coupled resonant nanowires along two orthogonal orientations to form angle-resolved photodetector arrays for spatial light localization of both static and moving objects with an error of less than 0.6 cm. These findings create a platform for self-assembled resonant nanostructures, thus paving the way for multifunctional nanophotonic and optoelectronic devices.

Adaptive In-Sensor Computing for Enhanced Feature Perception and Broadband Image Restoration

Traditional imaging systems struggle in weak or complex lighting environments due to their fixed spectral responses, resulting in spectral mismatches and degraded image quality. To address these challenges, a bioinspired adaptive broadband image sensor is developed. This innovative sensor leverages a meticulously designed type-I heterojunction alignment of 0D perovskite quantum dots (PQDs) and 2D black phosphorus (BP). This configuration enables efficient carrier injection control and advanced computing capabilities within an integrated phototransistor array. The sensor's unique responses to both visible and infrared (IR) light facilitate selective enhancement and precise feature extraction under varying lighting conditions. Furthermore, it supports real-time convolution and image restoration within a convolutional autoencoder (CAE) network, effectively countering image degradation by capturing spectral features. Remarkably, the hardware responsivity weights perform comparably to software-trained weights, achieving an image restoration accuracy of over 85%. This approach offers a robust and versatile solution for machine vision applications that demand precise and adaptive imaging in dynamic lighting environments.

Reconfigurable and nonvolatile ferroelectric bulk photovoltaics based on 3R-WS2 for machine vision

Hardware implementation of reconfigurable and nonvolatile photoresponsivity is essential for advancing in-sensor computing for machine vision applications. However, existing reconfigurable photoresponsivity essentially depends on the photovoltaic effect of p-n junctions, which photoelectric efficiency is constrained by Shockley-Queisser limit and hinders the achievement of high-performance nonvolatile photoresponsivity. Here, we employ bulk photovoltaic effect of rhombohedral (3R) stacked/interlayer sliding tungsten disulfide (WS2) to surpass this limit and realize highly reconfigurable, nonvolatile photoresponsivity with a retinomorphic photovoltaic device. The device is composed of graphene/3R-WS2/graphene all van der Waals layered structure, demonstrating a wide range of nonvolatile reconfigurable photoresponsivity from positive to negative ( ± 0.92 A W-1) modulated by the polarization of 3R-WS2. Further, we integrate this system with a convolutional neural network to achieve high-accuracy (100%) color image recognition at σ = 0.3 noise level within six epochs. Our findings highlight the transformative potential of bulk photovoltaic effect-based devices for efficient machine vision systems.

Ultrafast Intelligent Sensor for Integrated Biological Fluorescence Imaging and Recognition

Fluorescence imaging and recognition are core technologies in targeted medicine, pathological surgery, and biomedicine. However, current imaging and recognition systems are separate, requiring repeated data transfers for imaging and recognition that lead to delays and inefficiency, hindering the capture of rapidly changing physiological processes and biological phenomena. To address these problems, we propose an integrated intelligent sensor for biological fluorescence imaging and ultrafast recognition. This sensor integrates an imaging system based on a photodetector array and a recognition system based on neural networks on a single chip, featuring a highly compact structure, a continuously adjustable optical response, and reconfigurable electrical performance. The unified architecture of the imaging and recognition systems enables ultrafast recognition (19.63 μs) of tumor margins. Additionally, the special organic materials and bulk heterojunction structure endow the photodetector array with strong wavelength dependence, achieving high specific detectivity (3.06 × 1012 Jones) in the narrowband near-infrared range commonly used in biomedical imaging (600-800 nm). After training, the sensor can accurately recognize biological fluorescence edges in real time, even under interference from other colored light noise. Benefiting from its rapidity and high accuracy, we demonstrated a simulated surgical experiment showcasing tumor edge fluorescence imaging, recognition, and cutting. This integrated approach holds the potential to establish a novel paradigm for designing and manufacturing intelligent medical sensors.

An Aquatic Autonomic Nervous System

Reproducing human nervous systems with endogenous mechanisms has attracted increasing attention, driven by its great potential in streamlining the neuro-electronic interfaces with bilateral signaling. Here, an artificial aquatic autonomic nervous system (ANS) with switchable excitatory/inhibitory characteristics and acetylcholine (ACh)-mediated plasticity is reported based on the newly emerged organic photoelectrochemical transistor (OPECT). Under the modulation of spatial light and ACh, the system exhibits an immediate switch between excitation and inhibition, and many pulse patterns as well as advanced ANS functions are mimicked. To demonstrate its potential usage, the artificial ANS is then utilized to control artificial pupils and muscles to emulate real biological responses during an emergency. In contrast to previous solid-state attempts, this ANS is aqueous compatible just like biological nervous systems, which are capable of real neurotransmitter mediation.

Supercapacitively Liquid-Solid Dual-State Optoelectronics

Photo-transduction of solid-state optoelectronics occurs in semiconductors or their interfaces. Considering the confined active area and interfacial capacitance of solid-state materials, solid-state optoelectronics faces inherent limitations in photo-transduction, especially for bionic vision, and the performance is lower than that of living systems. For example, a photoreceptor generates pA-level photocurrent when absorbing a single photon. Here, a liquid-solid dual-state phototransistor is demonstrated, in which photo-transduction and modulation take place at the microporous interface between semiconductors and water, mimicking principles of the photoreceptor. When operating in the water, an orderly stacked photo-harvesting covalent organic framework layer generates supercapacitively photogating modulation of the channel conductivity via a dual-state interface, achieving responsivity of 4.6 × 1010 A W-1 and detectivity of 1.62 × 1016 Jones at room temperature, several orders of magnitude higher than other photodetectors. Such bio-inspired dual-state optoelectronics enables high-contrast scotopic neuromorphic imaging with responsivity greater than photoreceptors, holding promise for constructing optoelectronic systems with performance beyond conventional solid-state optoelectronics.

Unleashing the Potential: High Responsivity at Room Temperature of Halide Perovskite-Based Short-Wave Infrared Detectors with Ultrabroad Bandwidth

Short-wave infrared (SWIR) imaging systems offer remarkable advantages, such as enhanced resolution and contrast, compared to their optical counterparts. However, broader applications demand improvements in performance, notably the elimination of cryogenic temperature requirements and cost reduction in manufacturing processes. In this manuscript, we present a new development in SWIR photodetection, exploiting the potential of metal halide perovskite materials. Our work introduces a cost-effective and easily fabricated SWIR photodetector with an ultrabroad detection range from 900 to 2500 nm, a room-temperature responsivity of 1.57 × 102 A/W, and a specific detectivity of 4.18 × 1010 Jones at 1310 nm. We then performed comprehensive static and time-resolved optical and electrical measurements under ambient conditions, complemented by extensive density functional theory simulations, validating the formation of heterojunctions within the intrinsic n-type and extrinsic p-type perovskite structures. The potential of our perovskite-based SWIR materials extends from photodetectors to photovoltaic cells and introduces a possibility for high SWIR responsivity at room temperature and atmospheric pressure, which promotes its economic efficiency.

Graphene-Based Dual-Band Metasurface Absorber with High Frequency Ratio

In this paper, we propose a novel dual-band metasurface absorber with a high frequency ratio based on graphene. By carefully designing a centrally symmetrical graphene pattern and positioning it on a glass medium, while utilizing ITO as a ground, the metasurface absorber achieves remarkable high frequency ratio microwave absorption. Specifically, this metasurface absorber exhibits two distinct resonance points at 3.7 GHz and 14 GHz, with an impressive frequency ratio over 3.5. It achieves over 90% absorption efficiency in the frequency ranges of 3.5-4.5 GHz and 13.5-14.5 GHz, highlighting its capability to effectively absorb microwaves across widely spaced frequency bands. Furthermore, the metasurface absorber demonstrates optical transparency and polarization insensitivity, adding to its versatility and potential applications. The measured results of the fabricated prototype validate its design and potential for practical use.

Investigation of Graphene Single Layer on P-Type and N-Type Silicon Heterojunction Photodetectors

Photodetectors are of great interest in several technological applications thanks to their capability to convert an optical signal into an electrical one through light-matter interactions. In particular, broadband photodetectors based on graphene/silicon heterojunctions could be useful in multiple applications due to their compelling performances. Here, we present a 2D photodiode heterojunction based on a graphene single layer deposited on p-type and n-type Silicon substrates. We report on the electro-optical properties of the device that have been measured in dark and light conditions in a spectral range from 400 nm to 800 nm. The comparison of the device's performance in terms of responsivity and rectification ratio is presented. Raman spectroscopy provides information on the graphene single layer's quality and oxidation. The results showcase the importance of the doping of the silicon substrate to realize an efficient heterojunction that improves the photoresponse, reducing the dark current.

Photovoltage-Driven Photoconductor Based on Horizontal p-n-p Junction

The photoconductive gain theory demonstrates that the photoconductive gain is related to the ratio of carrier lifetime to carrier transit time. Theoretically, to achieve higher gain, one can either prolong the carrier lifetime or select materials with high mobility to shorten the transit time. However, the former slows the response speed of the device, while the latter increases the dark current and degrades device sensitivity. To address this challenge, a horizontal p-n-p junction-based photoconductor is proposed in this work. This device utilizes the n-region as the charge transport channel, with the charge transport direction perpendicular to the p-n-p junction. This design offers two advantages: (i) the channel is depleted by the space charge layer generated by the p and n regions, enabling the device to maintain a low dark current. (ii) The photovoltage generated in the p-n junction upon light absorption can compress the space charge layer and expand the conductive path in the n-region, enabling the device to achieve high gain and responsivity without relying on long carrier lifetimes. By adopting this device structure design, a balance between responsivity, dark current, and response speed is achieved, offering a new approach to designing high-performance photodetectors based on both traditional materials and emerging nanomaterials.

Negative Photoconductivity Transistors for Visuomorphic Computing

Visuomorphic computing aims to simulate and potentially surpass the human retina by mimicking biological visual perception with an artificial retina. Despite significant progress, challenges persist in perceiving complex interactive environments. Negative photoconductivity transistors (NPTs) mimic synaptic behavior by achieving adjustable positive photoconductivity (PPC) and negative photoconductivity (NPC), simulating "excitation" and "inhibition" akin to sensory cell signals. In complex interactive environments, NPTs are desired for visuomorphic computing that can achieve a better sense of information, lower power consumption, and reduce hardware complexity. In this review, it is started by introducing the development process of NPTs, while placing a strong emphasis on the device structures, working mechanisms, and key performance parameters. The common material systems employed in NPTs based on their functions are then summarized. Moreover, it is proceeded to summarize the noteworthy applications of NPTs in optoelectronic devices, including advanced multibit nonvolatile memory, optoelectronic logic gates, optical encryption, and visual perception. Finally, the challenges and prospects that lie ahead in the ongoing development of NPTs are addressed, offering valuable insights into their applications in optoelectronics and a comprehensive understanding of their significance.

Two-dimensional layered material photodetectors: what could be the upcoming downstream applications beyond prototype devices?

With distinctive advantages spanning excellent flexibility, rich physical properties, strong electrostatic tunability, dangling-bond-free surface, and ease of integration, 2D layered materials (2DLMs) have demonstrated tremendous potential for photodetection. However, to date, most of the research enthusiasm has been merely focused on developing novel prototype devices. In the past few years, researchers have also been devoted to developing various downstream applications based on 2DLM photodetectors to contribute to promoting them from fundamental research to practical commercialization, and extensive accomplishments have been realized. In spite of the remarkable advancements, these fascinating research findings are relatively scattered. To date, there is still a lack of a systematic and profound summarization regarding this fast-evolving domain. This is not beneficial to researchers, especially researchers just entering this research field, who want to have a quick, timely, and comprehensive inspection of this fascinating domain. To address this issue, in this review, the emerging downstream applications of 2DLM photodetectors in extensive fields, including imaging, health monitoring, target tracking, optoelectronic logic operation, ultraviolet monitoring, optical communications, automatic driving, and acoustic signal detection, have been systematically summarized, with the focus on the underlying working mechanisms. At the end, the ongoing challenges of this rapidly progressing domain are identified, and the potential schemes to address them are envisioned, which aim at navigating the future exploration as well as fully exerting the pivotal roles of 2DLMs towards the practical optoelectronic industry.

The Application of Multi-Parameter Multi-Modal Technology Integrating Biological Sensors and Artificial Intelligence in the Rapid Detection of Food Contaminants

Against the backdrop of continuous socio-economic development, there is a growing concern among people about food quality and safety. Individuals are increasingly realizing the critical importance of healthy eating for bodily health; hence the continuous rise in demand for detecting food pollution. Simultaneously, the rapid expansion of global food trade has made people's pursuit of high-quality food more urgent. However, traditional methods of food analysis have certain limitations, mainly manifested in the high degree of reliance on personal subjective judgment for assessing food quality. In this context, the emergence of artificial intelligence and biosensors has provided new possibilities for the evaluation of food quality. This paper proposes a comprehensive approach that involves aggregating data relevant to food quality indices and developing corresponding evaluation models to highlight the effectiveness and comprehensiveness of artificial intelligence and biosensors in food quality evaluation. The potential prospects and challenges of this method in the field of food safety are comprehensively discussed, aiming to provide valuable references for future research and practice.

Bio-Inspired Sensory Receptors for Artificial-Intelligence Perception

In the era of artificial intelligence (AI), there is a growing interest in replicating human sensory perception. Selective and sensitive bio-inspired sensory receptors with synaptic plasticity have recently gained significant attention in developing energy-efficient AI perception. Various bio-inspired sensory receptors and their applications in AI perception are reviewed here. The critical challenges for the future development of bio-inspired sensory receptors are outlined, emphasizing the need for innovative solutions to overcome hurdles in sensor design, integration, and scalability. AI perception can revolutionize various fields, including human-machine interaction, autonomous systems, medical diagnostics, environmental monitoring, industrial optimization, and assistive technologies. As advancements in bio-inspired sensing continue to accelerate, the promise of creating more intelligent and adaptive AI systems becomes increasingly attainable, marking a significant step forward in the evolution of human-like sensory perception.

Uncooled Broadband Photodetection via Light Trapping in Conformal PtTe2-Silicon Nanopillar Heterostructures

Dirac semimetals have demonstrated significant attraction in the field of optoelectronics due to their unique bandgap structure and high carrier mobility. Combining them with classical semiconductor materials to form heterojunctions enables broadband optoelectronic conversion at room temperature. However, the low light absorption of layered Dirac semimetals substantially limits the device's responsivity in the infrared band. Herein, a three-dimensional (3D) heterostructure, composed of silicon nanopillars (SiNPs) and a conformal PtTe2 film, is proposed and demonstrated to enhance the photoresponsivity for uncooled broadband detection. The light trapping effect in the 3D heterostructure efficiently promotes the interaction between light and PtTe2, while also enhancing the light absorption efficiency of silicon, which enables the enhancement of the device responsivity across a broadband spectrum. Experimentally, the PtTe2-SiNPs heterojunction device demonstrates excellent photoelectric conversion behavior across the visible, near-infrared, and long-wave infrared (LWIR) bands, with its responsivity demonstrating an order-of-magnitude improvement compared to the counterparts with planar silicon heterojunctions. Under 11 μm laser irradiation, the noise equivalent power (NEP) can reach 1.76 nW·Hz-1/2 (@1 kHz). These findings offer a strategic approach to the design and fabrication of high-performance broadband photodetectors based on Dirac semimetals.

Recent Progress in Wearable Near-Sensor and In-Sensor Intelligent Perception Systems

As the Internet of Things (IoT) becomes more widespread, wearable smart systems will begin to be used in a variety of applications in people's daily lives, not only requiring the devices to have excellent flexibility and biocompatibility, but also taking into account redundant data and communication delays due to the use of a large number of sensors. Fortunately, the emerging paradigms of near-sensor and in-sensor computing, together with the proposal of flexible neuromorphic devices, provides a viable solution for the application of intelligent low-power wearable devices. Therefore, wearable smart systems based on new computing paradigms are of great research value. This review discusses the research status of a flexible five-sense sensing system based on near-sensor and in-sensor architectures, considering material design, structural design and circuit design. Furthermore, we summarize challenging problems that need to be solved and provide an outlook on the potential applications of intelligent wearable devices.