- 标题
- 摘要
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- 实验方案
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Flexible and stretchable photodetectors and gas sensors for wearable healthcare based on solution-processable metal chalcogenides
摘要： Wearable smart sensors are considered to be the new generation of personal portable devices for health monitoring. By attaching to the skin surface, these sensors are closely related to body signals (such as heart rate, blood oxygen saturation, breath markers, etc.) and ambient signals (such as ultraviolet radiation, inflammable and explosive, toxic and harmful gases), thus providing new opportunities for human activity monitoring and personal telemedicine care. Here we focus on photodetectors and gas sensors built from metal chalcogenide, which have made great progress in recent years. Firstly, we present an overview of healthcare applications based on photodetectors and gas sensors, and discuss the requirement associated with these applications in detail. We then discuss advantages and properties of solution-processable metal chalcogenides, followed by some recent achievements in health monitoring with photodetectors and gas sensors based on metal chalcogenides. Last we present further research directions and challenges to develop an integrated wearable platform for monitoring human activity and personal healthcare.
关键词： gas sensor,photodetector,solution-processable metal chalcogenides,healthcare
更新于2025-09-12 10:27:22
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Improved growth conditions of pulsed laser-deposited PbI2 nanostructure film: towards high- photosensitivity PbI2/CNTs/Si photodetectors
摘要： Nanostructured PbI2 films were grown by laser deposition technique at a substrate temperature of 45?°C was demonstrated. Herein, we attempted to improve and control the crystal growth of PbI2 film and p-PbI2/MWCNTs/p-Si photodetector by finding the optimum laser fluence. X-ray diffraction XRD results illustrate that the grown PbI2 films are polycrystalline with hexagonal structure along (001) and the film crystallinity degraded with increasing the laser fluence. Scanning electron microscope SEM revealed that the particle size decreases as laser fluence increase and film deposited at 3.9?J/cm2 was dense and the grains distributed uniformly over the surface of the film. Energy dispersive X-ray EDX data confirms that the film stoichiometry depends on laser fluence and the film deposited at 3.9?J/cm2 was stoichiometric PbI2. The Photosensitivity investigations reveal that responsivity as high as 0.4 A/W at 610?nm was obtained for the p-PbI2/MWCNTs/p-Si photodetector prepared at 3.9?J/cm2 without post-deposition annealing.
关键词： photodetector,nanostructure film,PbI2,pulsed laser deposition,laser fluence
更新于2025-09-12 10:27:22
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Valence-State Controllable Fabrication of Cu <sub/> 2– <i>x</i> </sub> O/Si Type-II Heterojunction for High-Performance Photodetectors
摘要： Cuprite, nominally cuprous oxide (Cu2O) but more correctly Cu2-xO, is widely used in optoelectronic applications due to its natural p-type, nontoxicity and abundant availability. However, the photoresponsivity of Cu2O/Si photodetectors (PDs) has been limited by the lack of high-quality Cu2-xO films. Herein, we report a facile room-temperature solution method to prepare high-quality Cu2-xO films with controllable x value which were used as hole selective transport layers in crystalline n-type silicon based heterojunction PDs. The detection performance of Cu2-xO/Si PDs exhibits a remarkable improvement via reducing the x value, resulting in the optimized PDs with high responsivity of 417 mA W-1 and fast response speed of 1.3 μs. Furthermore, the performance of the heterojunction PDs can be further improved by designing the pyramidal silicon structure, with enhanced responsivity of 600 mA W-1 and response speed of 600 ns. The superior photodetecting performance of Cu2-xO/n-Si heterojunctions is attributed to (i) the matched energy level band alignment, (ii) the low trap states in high-quality Cu2O thin films, (iii) the excellent light trapping. We expect the low-cost, highly efficient solution process would be of great convenience for large-scale fabrication of the Cu2-xO thin films and broaden the applications of Cu2-xO based optoelectronic devices.
关键词： photodetector,energy band alignment,Cuprous oxide,solution method,heterojunction
更新于2025-09-12 10:27:22
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Beam offset detection in laser stake welding of tee joints based on photodetector sensing
摘要： This paper presents an experimental study where a photodetector is used in a laser beam welding tool to monitor beam deviations (beam offsets) in stake welding of tee joints. The aim is to obtain an early detection of deviations from the joint centerline in this type of welding where the joint is not visible from the top side. The photodetector used is a GaP diode sensitive in the spectral range 150-550 nm corresponding to the spectral emissions form the plasma plume during keyhole welding. The photodetector signal has been evaluated by change point detection methods with respect to their detection performance. Both an off-line and an on-line method have been evaluated. The off-line method can be used to guide post weld inspection and the on-line method has the potential to enable on-line adaptive position control and/or the possibility to stop the process for repair. The results shows that the proposed method can be used as a go/no go system and to guide post weld inspection.
关键词： process monitoring,tee joint,photodetector,laser beam welding
更新于2025-09-12 10:27:22
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Performance of polycrystalline GaN based metal-semiconductor-metal (MSM) photodetector with different contact
摘要： This paper describes performance of polycrystalline GaN based metal-semiconductor-metal (MSM) photodetector using different contact; Al, ITO, Ni and Pt. The performance of each photodetector was investigated in term of electrical resistivity (r ), signal-to-noise ratio (SNR), responsivity (R), internal quantum efficiency (η) and temporal responsivity. From the results, Ni is suggested to be a good contact for the photodetector. This is due to diffusion of NixO, formed by residual oxides on the GaN layer, into the Ni contact reduced the resistivity, thereby increasing the electrical conductivity of the photodetector. The photodetector with Ni contact demonstrated significant increase in SNR behavior with increasing bias voltage, while its r value was measured to be 2.02 M?.cm2, and η was 3.13%, 2.36% and 1.52%, at λ = 342 nm, 385 nm and 416 nm, respectively. From the temporal responsivity measurement, the rise time = 1.75 sec, the recovery time = 1.87 sec and the sensitivity = 5840%.
关键词： MSM photodetector,electrical contact,resistivity,internal quantum efficiency and temporal responsivity,signal-to-noise ratio,polycrystalline GaN,responsivity
更新于2025-09-12 10:27:22
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High Performance Van der Waals Graphene–WS <sub/>2</sub> –Si Heterostructure Photodetector
摘要： 2D materials have become a major focus in material science due to their exotic properties originated from quantum confinement effects. Van der Waals heterostructures composed of 2D materials and conventional semiconductors always show enhanced optoelectronic performance and have attracted much attention in recent years. Here, high performance photodetectors based on graphene–WS2–Si van der Waals heterostructure is reported. The photodetector shows wide spectrum response from visible to near infrared with a maximum photoresponsivity of 54.5 A W?1 at 800 nm. Furthermore, the photodetector has a fast response speed with rise time of 45 μs and decay time of 210 μs. Photocurrent mapping shows that not only the graphene–WS2–Si area, but also the graphene–WS2–SiO2–Si area contributes to the photocurrent. With the increase of lateral size of the junction area, the photoresponsivity is reduced due to increased recombination. The response speed decreases with the increase of lateral size of the junction area, which is due to increased junction capacitance. The results indicate that this kind of van der Waals heterostructure has excellent photodetection performance and is suitable for application in high performance broadband photodetectors. Also, the simple fabrication method has a great potential for large scale device integration.
关键词： van der Waals heterostructure,photodetector,WS2,graphene,Si
更新于2025-09-12 10:27:22
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Self-Powered Broad-band Photodetectors Based on Vertically Stacked WSe <sub/>2</sub> /Bi <sub/>2</sub> Te <sub/>3</sub><i>p–n</i> Heterojunctions
摘要： Semiconducting p-n heterojunctions, serving as the basic unit of modern electronic devices, such as photodetectors, solar-energy conversion devices, and light-emitting diodes (LEDs), have been extensively investigated in recent years. In this work, high performance self-powered broadband photodetectors were fabricated based on vertically stacked p-n heterojunctions though combining p-type WSe2 with n-type Bi2Te3 via van der Waals (vdW) epitaxial growth. Devices based on the p-n heterojunction show obvious current rectification behaviors in the dark and superior photovoltaic characteristics under light irradiation. Maximum short circuit current of 18 nA and open circuit voltage of 0.25 V can be achieved with the illumination light of 633 nm (power density: 26.4 mW/cm2), which are among the highest values compared with the ever reported 2D vdW heterojunctions synthesized by CVD method. Benefiting from the broadband absorption of the heterostructures, the detection range can be expanded from visible to near-infrared (375-1550 nm). Moreover, ascribing to the efficient carriers separation process at the junction interfaces, the devices can be further employed as self-powered photodetectors, where fast response time (≈210 μs) and high responsivity (20.5 A/W at 633 nm and 27 mA/W at 1550 nm) are obtained under zero bias voltage. The WSe2/Bi2Te3 p-n heterojunction-based self-powered photodetectors with high photoresponsivity, fast photoresponse time and broad spectral response will find potential applications in high speed and self-sufficient broadband devices.
关键词： p-n heterojunction,photodetector,photovoltaic,charge transfer,broadband,self-powered
更新于2025-09-12 10:27:22
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ZnO@graphene QDs with tuned surface functionalities formed on eco-friendly keratin nanofiber textile for transparent and flexible ultraviolet photodetectors
摘要： We demonstrate the ZnO@graphene core@shell quantum dot (ZGQDs) fabricated by selectively engineering of oxygenated functional groups on the graphene shells with eco-friendly keratin textile for transparent and flexible UV photodetector devices. The ZGQDs with the octylamine (ZGQDs-OA) and the graphene sheet were employed as an active material and an electron transport channel. The functional groups on the surrounding graphene shell in ZGQDs were passivated by the OA, resulting in a good absorbance in UV light and excellent carrier transport properties. The passivation of the functional groups on the graphene shell by OA drastically enhanced the photocurrent. Optical transmittance of the ZGQDs-OA/graphene sheets/PMMA/keratin nanofiber textile composites structures was approximately 77 % at the visible spectrum range. Current–voltage (I-V) and current–time (I-t) measurements on the UV photodetector under illumination state in bending condition exhibited the excellent ON/OFF switching states and stability. The photosensitivity and responsivity of the photodetector with ZGQDs-OA were found to be around 13.10 and 68.64 μAmW-1, respectively, which is much higher than that without the passivation. The improved performance of the photodetector with ZGQDs-OA could be attributed to the efficient electron transport to the electrode by the passivation of the graphene on ZnO QDs.
关键词： ZnO@graphene QDs,flexible device,photodetector,Eco-friendly,Textile
更新于2025-09-12 10:27:22
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Improved spectral and temporal response of MSM photodetectors fabricated on MOCVD grown spontaneous AlGaAs superlattice
摘要： A co-planar metal-semiconductor-metal nonsymmetrical back to back Schottky diode photodetector using natural superlattice AlGaAs grown by metalorganic vapor phase epitaxy on GaAs (100) has been reported. The detection efficiency and photoresponse of the superlattice based device are found significantly superior compared to the one based on high temperature annealed homogeneous AlGaAs. Under a forward bias of 1 V, the peak values of responsivity, detectivity and sensitivity were 10.133 mA/W, 7.6 × 1011 cmHz1/2W?1, 81.06 cm2/W for the device with as-grown natural superlattice and 1.14 mA/W, 7.05 × 1010 cmHz1/2W?1, 2.82 cm2/W for the device with homogeneous composition of AlGaAs, respectively. Besides, the device with natural superlattice structure showed much faster response to the pulsed light with rise and decay time of 560 μs and 1 ms as compared to 2 and 7 ms, respectively for the device with disordered bulk AlGaAs. The superior spectral and temporal characteristics of the device are explained by a model based on a third diode representing the net effect due to the superlattice modulations along with two Schottky diodes at the metal-semiconductor junctions. The third barrier, which is basically due to the periodic modulation in aluminium composition, plays an important role in enhancement of the photocurrent owing to the activation of the superlattice channels under light while keeping the dark current small. The fast sweeping of the photogenerated carries by the intrinsic electric field at the heterointerfaces in the active semiconducting layer makes the characteristic times of the device with the superlattice structures much smaller than one with homogeneous AlGaAs. Degradation in photoresponse and speed is attributed to the interdiffusion as an effect of thermal annealing.
关键词： AlGaAs/GaAs,Spectral response,Metal-semiconductor-metal photodetector,Natural superlattice,Temporal response
更新于2025-09-12 10:27:22
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Double perovskite Cs4CuSb2Cl12 microcrystalline device for cost effective photodetector applications
摘要： Recently reported double perovskites (DPs), Cs4CuSb2Cl12 has led to the development of a new lead free perovskite. It is 1 eV band gap material. The perovskite microcrystals were synthesized via liquid phase method. This was investigated as active solar energy materials for visible-light photodetector. The microcrystalline device was made in a single-step printable Cs4CuSb2Cl12/carbon materials composite paste. 10 wt % active material composite was found to be the best candidate for the highest responsivity, 10 ―3 A/W and detectivity, 108 J. One-step printing of the composite paste can be used for cost effective photodetector applications.
关键词： Photodetector,Solar energy materials,Cesium Copper Antimony Chloride (Cs4CuSb2Cl12),Carbon materials,Double Perovskite
更新于2025-09-12 10:27:22