Photosensitive Layer Research Articles

Bioinspired Three-Mode Photosensitive Synaptic LED for Optical Information Processing.

Inspired by human sense organs, AI is advancing toward multimodal perception, with display technology evolving into intelligent human-computer interaction tools. However, hardware networks with multimodal responses connected by different devices bring problems such as delayed information transfer and inefficiency. Thus, an innovative three-mode photosensitive synaptic LED (PSSL) is first proposed by adding a photosensitive layer indacenodithiophene-benzothiadiazole (IDTBT) to the quantum-dot light-emitting diode (QLED), switched by changing the bias voltage. The self-powered PSSL has a photoresponse range from 310 nm to 808 nm (ultraviolet-near-infrared, UV-NIR). The device exhibits a bipolar response under red and UV light at 1 V. When the voltage reaches the turn-on voltage, the PSSL device turns into a neuromorphic LED, exhibiting conductivity enhancement under red-light irradiation and suppression under UV-light irradiation. As a result, the PSSLs are expected to be applied in the field of optical encryption communication and in neuromorphic display.

Improving the photoswitching performance of a transistor with amorphous metal oxide semiconductor thin film by a gradient annealing approach

Metal oxides are attracting attention as electronic mate rials in research and industry. Thin films of amorphous indium gallium zinc oxide (a-IGZO) exhibit low absorbance in the visible spectrum, making them ideal components in transparent electronics. To widen the scope of use for thin film transistor (TFT) devices based on a-IGZO in on-chip sensing applications, photoresponsive behavior has been achieved by proper engineering of the active layers by either introducing a photosensitive top layer or using a method to generate localized states inside the band gap. In this paper, we propose a bilayer structured with the use of thermal annealing of a-IGZO film at different temperatures. Thermal annealing has been shown to improve the electrical performance of the TFT devices because of the improved film quality but negatively affects the photoresponsivity by removing tarp sites that play an important role in both charge generation and photomultiplication via the photogating effect. Therefore, here we propose an a-IGZO film with a high temperature-annealed bottom layer and pristine top layer. The bottom layer plays a vital role in the charge transport behavior, resulting in a low threshold voltage and subthreshold swing similar to the device with a fully annealed film, while the photoresponse of the device is driven by the higher density of gap states in the pristine top layer. This proposed method is advantageous to previously published procedures due to the simplicity of using no additional materials and complex steps to introduce trap sites into the photoactive layer, but only differential annealing temperature.

Process Development of a Liquid-Gated Graphene Field-Effect Transistor Gas Sensor for Applications in Smart Agriculture

A compact, multi-channel ionic liquid-gated graphene field-effect transistor (FET) has been proposed and developed in our work for on-field continuous monitoring of nitrate nitrogen and other nitrogen fertilizers to achieve sustainable and efficient farming practices in agriculture. However, fabricating graphene FETs with easy filling of ionic liquids, minimal graphene defects, and high process yields remains challenging, given the sensitivity of these devices to processing conditions and environmental factors. In this work, two approaches for the fabrication of our graphene FETs were presented, evaluated, and compared for high yields and easy filling of ionic liquids. The process difficulties, major obstacles, and improvements are discussed herein in detail. Both devices, those fabricated using a 3 μm-thick CYTOP® layer for position restriction and volume control of the ionic liquid and those using a ~20 nm-thick photosensitive hydrophobic layer for the same purpose, exhibited typical FET characteristics and were applicable to various application environments. The research findings and experiences presented in this paper will provide important references to related societies for the design, fabrication, and application of liquid-gated graphene FETs.

Multiple Narrowband Bidirectional Self‐Powered Organic Photodetector with Fast Response

AbstractBenefiting from the discovery of novel organic semiconductor materials bearing tunable absorption characteristics, narrowband organic photodetectors (OPDs) with improved performance are reported. Alongside new photoactive materials synthesis, several device engineering strategies are introduced to achieve narrowband OPDs, allowing less dependence of the device performance on the synthetic variation control, such as batch‐to‐batch differences in molecular weight. However, fabrication of multiband OPDs remains a challenge. Current solutions are usually based on vertical multi‐stacking of photosensitive layers with different absorption spectra and voltage‐modulated charge collection/injection, which renders the device fabrication too complex, while their response speed and band selectivity is limited. In this work, the concept of optical cavity is adopted to demonstrate self‐powered and fast response speed single‐junction bidirectional organic photodetectors with dual narrowband detection in the ultraviolet (UV) and visible part of the spectrum. Application of these devices in encrypted UV communication is successfully demonstrated. A third band in the near infrared (NIR) is possible to be isolated, rendering these high‐performing and simple to manufacture multiband OPD devices attractive for high‐resolution imaging and optical wireless communication.

Ultrafast response self-powered UV photodetectors based on ZnO/SiO2/Si heterojunction diodes

This paper presents ultrafast response, self-powered UV photodetectors (PDs) based on ZnO/SiO2/Si heterojunction diodes, utilizing zinc oxide (ZnO) nanorods as the photosensitive layer. This configuration results in photodetectors exhibiting unprecedentedly rapid response times, with rise and decay times reduced to 440 ns and 320 ns, respectively. Our study, focusing on ZnO nanorod PDs, not only demonstrates ultrafast response times but also highlights the role of hydrothermal synthesis temperature in tuning the devices’ performance. These findings represent a significant leap forward in the development of high-performance, self-powered UV PDs. The effects of different hydrothermal temperature on the morphology, crystal structure, and optoelectrical properties were systematically investigated using various characterization techniques, including field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) analysis, photoluminescence analysis, and current-voltage (I-V) measurements.

Efficient Dual‐Functional Quantum Dot Light‐Emitting Diodes with UV‐Vis‐NIR Broad‐Spectrum Photosensitivity

AbstractPhotosensitive quantum dot light‐emitting diodes (PSQLEDs) possess the dual capabilities of generating and detecting light signals, which is of significant importance for the development of miniaturized and integrated optoelectronic devices. However, the state‐of‐the‐art PSQLEDs can only detect light signals within a certain wavelength range, and require switching between the two functions under different bias voltage directions. In this work, The use of a ZnO/quantum dots (QDs)/ZnO multilayer (ZQZ ML) architecture as both the electron transport layer and the photosensitive layer is pioneered. The QDs in this structure are composed of narrow‐bandgap lead sulfide QDs and wide‐bandgap cadmium selenide QDs, successfully realizing a unique PSQLED device with C photosensitive characteristics. As a result, the as‐fabricated device can respond to illumination from 365 to 1300 nm, and the device achieves a photoresponse rate of 20.9 mA W−1 in self‐powered mode to UV light. After UV light irradiation, the maximum external quantum efficiency and maximum luminance of device reached 11.8% and 64,549 cd m−2, respectively. The device shows a record‐high luminance ON/OFF ratio of 5500%, which is beneficial for high contrast and accurate information display.

Imaging ultra-weak UV light below 100 pW cm-2 using a 4H-SiC photodetector with an Al2O3 interfacial layer.

Weak light detection is crucial in various practical applications such as night vision systems, flame monitoring, and underwater operations. Decreasing the dark current of a photodetector can effectively mitigate noises, consequently enhancing the signal-to-noise ratio and overall weak light detection performance. Herein, we demonstrate a 4H-SiC UV photodetector capable of detecting extremely weak UV light. This device comprises a photosensitive layer of 4H-SiC, two TiN electrodes and an atomically thin Al2O3 interfacial layer between TiN and the C surface of 4H-SiC. Under 360 nm UV light illumination, the proposed Al2O3 device demonstrates an ultra-low dark current of 18 fA, possibly benefiting from the effective passivation of interfacial carriers, and a boosted photo-to-dark current ratio of 6.7 × 107. Consequently, it achieves a weak-light detection limit as low as 31.8 pW cm-2, significantly outperforming the control device lacking Al2O3. When compared to previously reported SiC photodetectors, our Al2O3 device boasts an exceptional large linear dynamic range of 172 dB. Leveraging this, we construct a photodetector array capable of clearly imaging an object under ultra-weak light illumination below the 100 pW cm-2 level. The proposed photodetector represents a significant advancement in the development of highly sensitive image sensors for weak light detection.

Electrodeposition of Photosensitive Layers Based on Conducting Polymers and Zinc Phthalocyaninate, Their Structure and Photoelectrical Properties

Electrodeposition of Photosensitive Layers Based on Conducting Polymers and Zinc Phthalocyaninate, Their Structure and Photoelectrical Properties

36‐4: CQD‐Based Sensors for Large Format SWIR Imaging

Quantum dots have been rapidly developed in the display field, especially as photoluminescent color conversion layers. At the same time, quantum dots have also made increasing research progress in the detection field. We reported a short‐wave infrared sensor based on colloidal quantum dot technology. The photosensitive layer of the sensor uses HgTe colloidal quantum dot material. The detection band is 0.9~1.7um, the resolution is 1280*1024, and the pixel pitch is 15um. Colloidal quantum dot short‐wave infrared sensors get rid of the limitations of the indium pillar flip‐chip bonding process of traditional indium gallium arsenide CMOS short‐wave infrared focal plane sensors. The preparation process is simple, the yield is higher, and the cost is low. Based on the colloidal quantum dot shortwave infrared sensor, we implemented a shortwave infrared camera and characterized its performance parameters, and then we successfully captured shortwave infrared images through the shortwave infrared camera.

Highly uniform organic nanowire synaptic arrays with excellent performance for associative memory

Synaptic devices of optoelectronic nature, which combine light-detection and data-storage capabilities, hold significant promise in the realm of neuromorphic computing. They are especially beneficial for the processing of visual data and the execution of intricate cognitive functions akin to learning, memory retention, and logical reasoning. However, current research is mostly confined to the level of individual devices, with corresponding studies on synaptic arrays being relatively scarce. Type II heterojunctions are widely used in optoelectronics. Bandgap engineering enables efficient separation and trapping of photogenerated excitons in selected materials, reducing carrier recombination. This prolongs carrier retention in the channel, delaying photocurrent decay, crucial for artificial optoelectronic synapses. We designed an organic nanowire/perovskite Type II heterojunction where CsPbBr3 perovskite films and TIPS nanowires serve as the photosensitive and channel layers, respectively. The composite synaptic array was successfully fabricated by in-situ growth of TIPS nanowires on the surface of perovskite thin films. It was further used to fabricate a photonic synapse array that exhibits characteristic photocurrent and stable optical response. Achieving high-performance photonic synapses was facilitated by characteristics such as high mobility and high on/off ratios, stemming from the formation of complete single-crystal nanowires on the perovskite films. Exhibiting synaptic behaviors such as photo-induced enhancements and paired-pulse facilitation, the device enabled a visual sensing system with a 5 × 5 pixel array for simulating memory processes and restoring associative memories. A novel photocurrent model was established for understanding device characteristics. This work provides valuable insights for future utilization of composite organic nanowire arrays in simulating brain-like computations and realizing large-scale intelligent visual sensing systems.

UV‐A/B High‐Sensitivity Organic Photodetectors Containing Butterfly‐Shaped Furan‐Fused BN‐Dihydropyrene with Push‐Pull Electron “Wings” toward Image Sensor

AbstractReplacement of C─C unit with its isoelectronic B─N unit in aromatics provides a new class of molecules with appealing properties. Herein, Five novel butterfly‐shaped furan‐fused bis‐BN dihydropyrenes (FBN) derivatives are synthesized with different push‐pull electron “wings”. These compounds exhibit prominent UV‐A/B absorption, high energy levels, and p‐type characteristics. Thanks to the side‐chain engineering and BN dipole manipulation, their intramolecular dipole moments and intermolecular stacking mode are effectively regulated to improve intra‐ and inter‐molecular charge transfer, thus achieving high hole mobilities. Five FBN‐X compounds are doped with PC71BM as heterojunction photosensitive layers to fabricate solution‐processed high performance organic photodetectors (OPDs), which exhibit self‐powered effect and high sensitivity to UV‐A/B. Especially, the FBN‐CN‐based device presents a high detectivity up to 1.72 × 1012 Jones, a peak external quantum efficiency of 19.1%, and an extremely low dark current density of 8.90 × 10−10 A cm−2 under 320 nm at 0 V. To the best of authors knowledge, it is the first report of photodiode‐type UV‐OPDs containing BN‐doped polycyclic aromatic hydrocarbons as active layer to date. And the optimal device shows a significant advantage over the reported 300–380 nm UV‐OPDs. In addition, a 10 × 10 array of organic image sensor is successfully demonstrated, which showcases excellent low‐light imaging capability.

Effective Strategy for High‐Performance Organic Photodetectors with Significantly Suppressed Dark Current and Improved Responsivity

AbstractOrganic photodetectors (OPDs) have attracted immense interest as solution‐processable optical signal‐capturing devices due to their various advantages, such as adjustable response range, excellent weak light response, lightweight, flexibility, and ease of processing on diverse substrates. Low dark current density (Jd) and high responsivity (R) are key requirements necessary for achieving a high specific detectivity (D*). Here, an effective strategy for preparing high‐performance OPDs with potential micro p‐i‐n structure by introducing insulating poly(aryl ether) (PAEN) into the organic photosensitive layer is reported. The PM6:PC71BM‐based OPDs are capable of significantly suppressing Jd while increasing R, which can be attributed to the multiple optimizations of morphology and charge transport caused by the addition of PAEN. As a result, the value of Jd (3.63 × 10−10 A cm−2) is two orders of magnitude lower than that of the device without PAEN (1.00 × 10−8 A cm−2) at −1 V bias. Combined with the increased R of 0.376 A W−1, the optimized device achieves a high D*of 3.45 × 1013 Jones (−1 V at 620 nm). The optimized OPDs demonstrate high performance that is comparable to commercial Si photodetectors (Hamamatsu S1133), paving the way for the direct market development of this cost‐effective organic photodetection technology.

Enhanced photosensitivity in a hybrid WSe2/2DEG heterojunction using a buried TiO2 photosensitive layer

In this study, we integrated the wide-bandgap material TiO2 as a photosensitive layer with the WSe2/2DEG heterostructure, creating a hybrid WSe2/TiO2/2DEG heterojunction. This hybrid structure significantly improves the device’s photosensitivity, exhibiting a high rectification effect and a switching ratio of 103. The photodetector shows excellent performance, with a responsivity of 0.61 A W−1 and a detectivity of up to 1.1×1011 Jones at 405 nm, along with a very fast photoresponse speed. The buried TiO2 channel allows photogenerated electrons to easily flow through the reduced barrier at the depleted region. This hybrid heterojunction holds promise for the development of high-performance photoelectric devices.

Activation of the Photosensitive Potential of 2D GaSe by Interfacial Engineering.

Two-dimensional (2D) gallium selenide (GaSe) holds great promise for pioneering advancements in photodetection due to its exceptional electronic and optoelectronic properties. However, in conventional photodetectors, 2D GaSe only functions as a photosensitive layer, failing to fully exploit its inherent photosensitive potential. Herein, we propose an ultrasensitive photodetector based on out-of-plane 2D GaSe/MoSe2 heterostructure. Through interfacial engineering, 2D GaSe serves not only as the photosensitive layer but also as the photoconductive gain and passivation layer, introducing a photogating effect and extending the lifetime of photocarriers. Capitalizing on these features, the device exhibits exceptional photodetection performance, including a responsivity of 28 800 A/W, specific detectivity of 7.1 × 1014 Jones, light on/off ratio of 1.2 × 106, and rise/fall time of 112.4/426.8 μs. Moreover, high-resolution imaging under various wavelengths is successfully demonstrated using this device. Additionally, we showcase the generality of this device design by activating the photosensitive potential of 2D GaSe with other transition metal dichalcogenides (TMDCs) such as WSe2, WS2, and MoS2. This work provides inspiration for future development in high-performance photodetectors, shining a spotlight on the potential of 2D GaSe and its heterostructure.

Emerging Frontiers of 2D Transition Metal Dichalcogenides in Photovoltaics Solar Cell

AbstractTwo‐dimensional (2D) transition metal dichalcogenides (TMDCs) have gained much attention due to their excellent electronic and optoelectronic properties. The reasonable band gap, higher light‐matter interaction, hundreds of categories as well as wafer‐scale growth and Si‐compatible fabrication etc. proof their immense potential for next‐generation solar cells. Over the past years, a variety of specific device structure are investigated including multi‐field tunable 2D TMDCs‐based photovoltaic solar cell since its electronic structure is easily tunable. Their work function distributes in a wide range which facilitate interfacial modulation and optimize the electron/hole transfer layer in perovskite‐/organic‐based photovoltaic solar cell. In this review, the recent developments of TMDCs in photovoltaic solar cell are comprehensively described. First, the energy diagram of traditional semiconductor and 2D TDMCs are discussed. Then, 2D TMDCs‐based photovoltaic solar cell is introduced considering the homojunction, heterojunction and Schottky‐junction as well as their multi‐field tunability. Third, the role of 2D TMDCs layer as photosensitive layer and modifying layer in silicon‐based solar cells, as well as their applications in perovskite‐/organic‐based solar cells are summarized considering their role of electron/hole transfer layer or active layer. Lastly, the prospect for future materials, device and process trends and practical applications of TMDCs‐based photovoltaic solar cell are presented.

Nano-structuration influence on the polyimide-based spatial light modulator’s parameters

The classical and the nano-structured spatial light modulators (SLMs) especially based on the polyimide photosensitive layers, as the key element of the optoelectronic devices, display, and telecommunications schemes are considered. The main emphasis is placed on the device with a polyimide photo-layer due to its high sensitivity and acceptable performance. A modulator’s basic characteristics are studied taken into account the comparison with the different types of the photo-layers, such as: ZnSe, ZnS, a-Si:H. Liquid crystal (LC) media is considered as the modulation system. It is indicated that the different methods and approaches are applied for investigation of the basic SLM parameters, such as: Z-scanning technique, third harmonic generation, four-wave mixing set-up, etc. In the current paper the laser holographic technique is used to investigate the resolution, sensitivity, and speed of the LC-SLM devices. The influence of the fullerene doping on the organic photo-layers based on the polyimide materials is presented. This influence of this nano-structuration process on the modulator’s basic parameters is discussed.

Comparison of the effects of EGF, FGF-b, and NGF on the proliferation, migration, and reprogramming of primary rat Müller cells.

During the healing process of full-thickness macular holes (FTMHs), the closure and recovery of the hole depend on the migration, proliferation, and activation of Müller cells to promote the closure of holes and restoration of the photosensitive layer. In this study, we investigated the ability of the epidermal growth factor (EGF), fibroblast growth factor-basic (FGF-b), and nerve growth factor (NGF) to influence this process by regulating proliferation, migration, and reprogramming of primary rat Müller cells. Cell proliferation was measured using CCK8 [2- (2-Methoxy-4-nitrophenyl)-3- (4-nitrophenyl)-5- (2,4-disulfophenyl)-2H-tetrazolium Sodium Salt] colorimetric assays and EdU [5-Ethynyl-2'-deoxyuridine] assays over 48 h. Cell migration was measured using scratch-wound assays and transwell migration assays over 48 h. In addition, we conducted Western blot assays and immunofluorescence assays on cells that were specially treated for 1, 3, and 5 days for cell reprogramming. The percentage of EdU-positive cells in Nestin-positive have also been tested by co-immunofluorescence (Co-IF) staining. EGF and FGF-b significantly promoted the proliferation of Müller cells (p < 0.05) at a concentration of 0-50 ng/mL, but NGF did not (p > 0.05), compared to untreated controls. Exogenous FGF-b and EGF promote the reprogramming of primary rat Müller cells, significantly enhancing the neural stem cell marker Nestin after stimulation on the 1st, 3rd, and 5th days, respectively. The expression of Müller cell marker Vimentin was significantly (p < 0.05) reduced during this period compared to the control group. However, there was no significant difference between the NGF and control groups. Furthermore, the EGF group expressed stronger Nestin expression than the SCM group. The Co-IF staining showed that early 50% of activated cells came from newly proliferating cells on the 5th day. These observations suggest that FGF-b can promote the activation of Müller cells in a short time and enhance the possessive features of neural stem cells, while EGF may act for a longer period of time. This may further the understanding of growth factor therapy in treating FTMHs, and Müller glia may be promising candidates for cell replacement therapy.

Retinomorphic Photonic Synapses for Mimicking Ultraviolet Radiation Sensing and Damage Imaging

AbstractPhotonic synapses integrate sensing and processing within a single device, making them promising candidates for emulating the visual perception of a biological retina. Most retinomorphic photonic synapses achieve image pre‐processing by differentially responding to red, green, and blue (RGB). However, the impact of invisible ultraviolet (UV) light on the retina remains insufficiently explored, hindering the perception of the full spectrum by retinomorphic devices. Herein, a photonic synapse is constructed with strong UV absorption of Poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐co‐(4,4′‐(N‐(4‐sec‐butylphenyl) diphenylamine)] (TFB) as photosensitive layer. The device exhibits synaptic properties of long‐term memory (LTM) and short‐term memory (STM) at different UV radiation stages. Extracting the electrical conductance of the device under UV radiation generates patterns of different resolutions, facilitating the simulation of retinal damage's impact on object perception. Moreover, an electronic eye system, incorporating the photonic synapse under UV radiation, successfully replicates pupil constriction and eye‐closing behaviors akin to those observed in a real biological eye. This result underscores the authenticity of retinomorphic devices, expending a novel concept for the future development of visuomorphic computing.

Dry‐Wet Hybrid Direct Printing of Laser‐Induced Graphene and Zinc Oxide Nanoribbons for Continuous‐Flow Manufacturing of Flexible Wearable Photodetectors

AbstractFlexible wearable electronics enable an in situ and real‐time measurement of human physiology and micro‐environment. Although large‐scale production of flexible wearable electronics is demonstrated using direct printing techniques, the “wet” nature of these techniques requires multiple procedures and chemicals to prepare printable inks, increasing the complexity and cost. Here, a dry‐wet hybrid direct printing is developed for the mass production of flexible wearable photodetectors, in which a “dry” direct laser writing and a “wet” screen printing are employed to fabricate laser‐induced graphene as electrode layer and zinc oxide as photosensitive layer, respectively. The liquid‐free fabrication of LIG significantly reduces the complexity and cost of the production. An automatic conveyor belt is designed to realize continuous‐flow manufacturing. The photodetectors demonstrate good ultraviolet (UV) photodetection performances, such as a photo‐to‐dark current ratio (Iphoto/Idark) of 5.67 × 105, approaching the record of similar devices. The manufacturing system presents a high reproducibility, considering that Iphoto/Idark only fluctuates within 7.10%. The flexible photodetectors are worn as wristbands after being integrated with a data acquisition and transmission circuit. UV intensity is real‐time monitored on a self‐developed mobile application. The continuous‐flow manufacturing based on the developed dry‐wet hybrid direct printing sheds light on the mass production of flexible wearable electronics.

Optical and ultrasonic dual-sensitive sensor and its application in photoacoustic microscopy

Multi-modality imaging is significant for biomedical applications. We propose a dual-sensitive sensor to simultaneously detect optical and ultrasonic signals. Based upon the classical piezoelectric structure, we attach a photosensitive layer made of carbon nanotubes-polydimethylsiloxane (CNTs-PDMS) composite to the surface. The photosensitive layer absorbs light and converts it into ultrasound, while allowing acoustic energy to transmit through concurrently. After optimizing the ratio of PDMS to CNTs, we increase the sensor’s light detection sensitivity and maintain the ultrasound detection sensitivity. Finally, the successful implementation in mouse ear optical attenuation–photoacoustic imaging demonstrates the dual-sensitive sensor’s potential application in multi-modality imaging.