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Solution-processed phototransistors can substantially advance the performance of image sensors. Phototransistors exhibit large photoconductive gain and a sublinear responsivity to irradiance, which enables a logarithmic sensing of irradiance that is akin to the human eye and has a wider dynamic range than photodiode-based image sensors. Here, we present a novel solution-processed phototransistor composed of a heterostructure between a high-mobility organic semiconductor and an organic bulk heterojunction. The device efficiently integrates photogenerated charge during the period of a video frame then quickly discharges it, which significantly increases the signal-to-noise ratio compared with sampling photocurrent during readout. Phototransistor-based image sensors processed without photolithography on plastic substrates integrate charge with external quantum efficiencies above 100% at 100 frames per second. In addition, the sublinear responsivity to irradiance of these devices enables a wide dynamic range of 103 dB at 30 frames per second, which is competitive with state-of-the-art image sensors. A solution-processed organic phototransistor is operated at 100-frame-per-second rates with external quantum efficiencies above 100%. Dynamic range as high as 103 dB was shown for 30-frame-per-second operation.

Multi-sensory neuromorphic devices (MND) have broad potential in overcoming the structural bottleneck of von Neumann in the era of big data. However, the current multisensory artificial neuromorphic system is mainly based on unitary nonvolatile memory or volatile synaptic devices without intrinsic thermal sensitivity, which limits the range of biological multisensory perception and the flexibility and computational efficiency of the neural morphological computing system. Here, a temperature-dependent memory/synaptic hybrid artificial neuromorphic device based on floating gate phototransistors (FGT) is fabricated. The CsPbBr 3 /TiO 2 core-shell nanocrystals (NCs) prepared by in-situ pre-protection low-temperature solvothermal method were used as the photosensitive layer. The device exhibits remarkable multi-level visual memory with a large memory window of 59.6 V at room temperature. Surprisingly, when the temperature varies from 20 to 120 °C back and forth, the device can switch between nonvolatile memory and volatile synaptic device with reconfigurable and reversible behaviors, which contributes to the efficient visual/thermal fusion perception. This work expands the sensory range of multisensory devices and promotes the development of memory and neuromorphic devices based on organic field-effect transistors (OFET).

Recently, the emerging 2D materials MXene have gained a surge of attention to the production of optoelectronics devices such as solar cells, plasmonic, phototransistors, photodetectors, light‐emitting diodes, photothermal therapy, and so on. Its outstanding optical and electrical characteristics, unique structure, and large specific surface area make it suitable for future use in modern optoelectronics including ultrafast lasers, light emitters, modulators, and plasmonic generators. There is a lack of critical analysis on the prospects, challenges, overview of synthesis methods, mechanisms, and future research directions of MXene despite having some reviews have been published on the applications of MXene. Therefore, this study critically analyzed the existing challenges of MXene, such as poor stability in an oxygen environment, inadequate mechanical properties, ease of stacking, temperature barrier, and so on. In addition, the fundamentals, preparation techniques, properties, and applications of MXene have been summarized. The mechanism, limitations, and benefits of different preparation methods have been mentioned. A comprehensive analysis and guidelines have been provided to improve the existing synthesis methods. The ways to overcome these challenges, prospects, and future markets of the MXene‐based optoelectronic devices have been described. This review provides an overview of the fundamentals, preparation techniques, properties, and applications of MXene, along with addressing the mechanism, limitations, and potential benefits of various methods of MXene preparation. The present paper also explores the ways that we can overcome the current challenges and provide a roadmap to the future of MXene in different fields of optoelectronics.

Motion processing has proven to be a computational challenge and demands considerable computational resources. Contrast this with the fact that flying insects can agilely perceive real-world motion with their tiny vision system. Here we show that phototransistor arrays can directly perceive different types of motion at sensory terminals, emulating the non-spiking graded neurons of insect vision systems. The charge dynamics of the shallow trapping centres in MoS 2 phototransistors mimic the characteristics of graded neurons, showing an information transmission rate of 1,200 bit s −1 and effectively encoding temporal light information. We used a 20 × 20 photosensor array to detect trajectories in the visual field, allowing the efficient perception of the direction and vision saliency of moving objects and achieving 99.2% recognition accuracy with a four-layer neural network. By modulating the charge dynamics of the shallow trapping centres of MoS 2 , the sensor array can recognize motion with a temporal resolution ranging from 10 1 to 10 6  ms. Inspired by the visual systems of agile insects, Chen et al. emulate their graded neurons using optoelectronic devices to realize bioinspired in-sensor motion perception and demonstrate high recognition accuracy with limited computational resources.

In-sensor processing, which can reduce the energy and hardware burden for many machine vision applications, is currently lacking in state-of-the-art active pixel sensor (APS) technology. Photosensitive and semiconducting two-dimensional (2D) materials can bridge this technology gap by integrating image capture (sense) and image processing (compute) capabilities in a single device. Here, we introduce a 2D APS technology based on a monolayer MoS 2 phototransistor array, where each pixel uses a single programmable phototransistor, leading to a substantial reduction in footprint (900 pixels in ∼0.09 cm 2 ) and energy consumption (100s of fJ per pixel). By exploiting gate-tunable persistent photoconductivity, we achieve a responsivity of ∼3.6 × 10 7  A W −1 , specific detectivity of ∼5.6 × 10 13  Jones, spectral uniformity, a high dynamic range of ∼80 dB and in-sensor de-noising capabilities. Further, we demonstrate near-ideal yield and uniformity in photoresponse across the 2D APS array. Low-power and compact active pixel sensor (APS) matrices are desired for resource-limited edge devices. Here, the authors report a small-footprint APS matrix based on monolayer MoS 2 phototransistors arrays exhibiting spectral uniformity, reconfigurable photoresponsivity and de-noising capabilities at low energy consumption.

Wavelength selective imaging has a wide range of applications in image recognition and other application scenarios, which can effectively improve the recognition rate of objects. However, in the existing technical scenarios, it is usually necessary to use complex optical devices such as filters or gratings to achieve wavelength extraction. These methods inevitably bring about the problems of complex structure and low integration. Therefore, it is necessary to realize the wavelength extraction function at the device level. Here, we realize the wavelength extraction function and wide‐spectrum imaging function in the visible to infrared band based on a visible light absorber/floating gate storage layer/near‐infrared (NIR) photogating layer configuration. Under infrared irradiation, the device exhibits negative photoresponse through the absorption of infrared light by the Ge substrate and the photogating effect, and realizes visible positive light response through the absorption of visible light by MoS2. Utilizing the memory function of the device, by cleverly changing the gate voltage pulse, the photoresponse state of the output voltage is effectively adjusted to achieve three imaging states: visible light response only, response to both visible and infrared light, and infrared light response only. Active selective imaging of the word “XDU” was achieved at 532 and 1550 nm wavelength. By using the photoresponse data of the device, the passive imaging of the topography of Xi'an, Shaanxi Province was obtained, which effectively improves the recognition rate of mountains and rivers. The proposed reconfigurable visible–infrared wavelength‐selective imaging photodetector can effectively extract image information and improve the image recognition rate while ensuring a simple structure. The single‐chip‐based spectral separation imaging solution lays a good foundation for the further development of visible–infrared vision applications. The Ge‐based MoS2 floating‐gate phototransistor achieves good storage characteristics and bidirectional light response functions. Based on this characteristic, the wavelength extraction function from visible to infrared is realized at the device level, which effectively reduces the structural complexity of the system and improves the image recognition rate.

Porous silicon nanowires enable optical switching and electrical current amplification in a photon-triggered transistor. Photon-triggered electronic circuits have been a long-standing goal of photonics. Recent demonstrations include either all-optical transistors in which photons control other photons 1 , 2 or phototransistors with the gate response tuned or enhanced by photons 3 , 4 , 5 . However, only a few studies report on devices in which electronic currents are optically switched and amplified without an electrical gate. Here we show photon-triggered nanowire (NW) transistors, photon-triggered NW logic gates and a single NW photodetection system. NWs are synthesized with long crystalline silicon (CSi) segments connected by short porous silicon (PSi) segments. In a fabricated device, the electrical contacts on both ends of the NW are connected to a single PSi segment in the middle. Exposing the PSi segment to light triggers a current in the NW with a high on/off ratio of >8 × 10 6 . A device that contains two PSi segments along the NW can be triggered using two independent optical input signals. Using localized pump lasers, we demonstrate photon-triggered logic gates including AND, OR and NAND gates. A photon-triggered NW transistor of diameter 25 nm with a single 100 nm PSi segment requires less than 300 pW of power. Furthermore, we take advantage of the high photosensitivity and fabricate a submicrometre-resolution photodetection system. Photon-triggered transistors offer a new venue towards multifunctional device applications such as programmable logic elements and ultrasensitive photodetectors.

This work reports the performance improvements of solar-blind ultraviolet n-Al 0.5 GaN/AlN field-effect phototransistors by inserting an undoped Al 0.5 GaN interface layer. The dark current has been reduced by one magnitude, while the photocurrent has been amplified by two magnitudes. The spectral rejection ratio of 250 to 290 nm is 2.65 × 10 6 at 10 V, over 10 4 times higher than the control sample. Also, the stability of periodic photoresponse has been significantly improved. These superior performances result from the enhancement of electron depletion and the reduction of deep level defects in the channel brought by the insertion layer.

Infrared-to-visible upconversion devices made by integrating an infrared quantum dot photodetector with an organic light-emitting diode potentially offer a route to low-cost, pixel-free infrared imaging. However, making such devices sufficiently efficient for practical use is a challenge. Here, we report a high-gain vertical phototransistor with a perforated metallic source electrode having an EQE up to 1 × 10 5 % and a detectivity of 1.2 × 10 13  Jones. By incorporating a phosphorescent organic light-emitting diode in this phototransistor, an infrared-to-visible upconversion LEPT with a photon-to-photon conversion efficiency of over 1,000% is demonstrated. An optoelectronic device that efficiently converts infrared light to visible light could prove useful for imaging applications.

Low dimensional materials including quantum dots, nanowires, 2D materials, and so forth have attracted increasing research interests for electronic and optoelectronic devices in recent years. Photogating, which is usually observed in photodetectors based on low dimensional materials and their hybrid structures, is demonstrated to play an important role. Photogating is considered as a way of conductance modulation through photoinduced gate voltage instead of simply and totally attributing it to trap states. This review first focuses on the gain of photogating and reveals the distinction from conventional photoconductive effect. The trap‐ and hybrid‐induced photogating including their origins, formations, and characteristics are subsequently discussed. Then, the recent progress on trap‐ and hybrid‐induced photogating in low dimensional photodetectors is elaborated. Though a high gain bandwidth product as high as 109 Hz is reported in several cases, a trade‐off between gain and bandwidth has to be made for this type of photogating. The general photogating is put forward according to another three reported studies very recently. General photogating may enable simultaneous high gain and high bandwidth, paving the way to explore novel high‐performance photodetectors. Photogating is considered as a way of conductance modulation through photoinduced voltage. The origins, formations, and characteristics of the trap‐ and hybrid‐induced photogating are discussed. This type of photogating enables a trade‐off between gain and bandwidth. However, general photogating may enable simultaneous high gain and high bandwidth, paving the way to explore novel high‐performance photodetectors.