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Ultrathin All-2D Lateral Graphene/GaS/Graphene UV Photodetectors by Direct CVD Growth
摘要： UV-sensitive lateral all-two-dimensional (2D) photodetecting devices are produced by growing the large band gap layered GaS between graphene electrode pairs directly using chemical vapor deposition methods. The use of prepatterned graphene electrode pairs on the Si wafer enables more than 200 devices to be fabricated simultaneously. We show that the surface chemistry of the substrate during GaS leads to selective growth in graphene gaps, forming the lateral heterostructures, rather than on the surface of graphene. The graphene/GaS/graphene lateral photodetecting devices are demonstrated to be sensitive to UV light only, with no measurable response to visible light. Furthermore, we demonstrate UV-band discrimination in photosensing, with measured photocurrents only produced for middle-UV and not for near-UV wavelength regions. The detection limit could reach down to 2.61 μW/cm2 with a photoresponsivity as high as 11.7 A/W and a photo gain of 53.7 under 270 nm excitation. Gate-dependent modulation of the photocurrent is also demonstrated. The photodetectors exhibit long-term stability and reproducible ON?OFF switching behavior, with a response time lower than 60 ms. These results provide insights into how ultrathin UV sensing devices can be created using only 2D materials by exploiting large band gap 2D semiconductors such as GaS.
关键词： CVD,2D optoelectronics,GaS,photodetector,UV,graphene
更新于2025-09-12 10:27:22
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Coupled Quantum Wells
摘要： Intersubband transitions in ZnO material systems are predicted to be promising candidates for infrared and terahertz (THz) optoelectronic devices due to their unusual material properties. In particular, the temperature performance of THz quantum cascade lasers is postulated to be significantly enhanced using ZnO material systems due to their large optical phonon energy. Taking a step forward toward that goal, intersubband transitions in ZnO/MgxZn1?xO asymmetric coupled quantum wells are observed on a nonpolar m plane ZnO substrate. Two absorption peaks are observed in the energy range from approximately 250 meV to approximately 410 meV at room temperature, unambiguously demonstrating the interwell coupling in the asymmetric coupled quantum wells. A theoretical model taking into account the interaction between intersubband transitions shows reasonable overall agreement with the experimental results, thus proving the strong coupling nature of the investigated system. As the building block of complex quantum structures based on intersubband transitions, the results presented show great potential applications of ZnO/MgxZn1?xO material systems in infrared and THz optoelectronics and physics.
关键词： intersubband transitions,ZnO,optoelectronics,quantum wells,THz,infrared
更新于2025-09-12 10:27:22
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Light or Heat: What Is Killing Lead Halide Perovskites Under Solar Cell Operation Conditions?
摘要： We report the first systematic assessment of intrinsic photothermal stability of a large panel of complex lead halides APbX3 incorporating different univalent cations (A=CH3NH3+, [NH2CHNH2]+, Cs+) and halogen anions (X=Br, I) using a series of analytical techniques such as UV-vis and x-ray photoelectron spectroscopy, x-ray diffraction, EDX analysis, atomic force and scanning electron microscopy, ESR spectroscopy and mass spectrometry. We show that heat stress and light soaking induce a severe degradation of perovskite films even in the absence of oxygen and moisture. The stability of complex lead halides increases in the order MAPbBr3<MAPbI3<FAPbI3<FAPbBr3<CsPbI3<CsPbBr3, thus featuring all-inorganic perovskites as the most promising absorbers for stable perovskite solar cells. An important correlation was found between the stability of the complex lead halides and the volatility of univalent cation halides incorporated in their structure. The established relationship provides useful guidelines for designing new complex metal halides with immensely improved stability.
关键词： Plasmonics and Optoelectronics,Photothermal Stability,Solar Cell Operation Conditions,Energy Conversion and Storage,Lead Halide Perovskites
更新于2025-09-12 10:27:22
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High‐Temperature Optical Characterization of GaN‐Based LEDs for Future Power Electronic Modules
摘要： High-temperature optical analysis of three different InGaN/GaN MQW LED structures (peak wavelength λp = 448nm, 467 nm & 515nm) is conducted for possible integration as an optocoupler emitter in high-density power electronic modules. The commercially available LEDs, primarily used in the display (λp = 467 nm & 515nm) and lighting (λp = 448nm) applications, are studied and compared to evaluate if they can satisfy the light output requirements in the optocouplers at high temperatures. The temperature- and intensity-dependent electroluminescence (T-IDEL) measurement technique is used to study the internal quantum efficiency (IQE) of the LEDs. All three LEDs exhibits above 70 % IQE at 500 K, and stable operation at 800 K without flickering or failure. At 800K, a promising IQE of above 40 % is observed for blue for display (λp = 467 nm) and green for display (λp = 515nm) samples. Blue for light (λp = 448nm) sample shows 24 % IQE at 800 K.
关键词： high-temperature optoelectronics,high-density power modules,optocouplers,quantum efficiency
更新于2025-09-12 10:27:22
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Advanced Thermoelectric Materials for Energy Harvesting Applications || Thermoelectric Control of Deep UV LED to Improve Optical Performance
摘要： A thermoelectric control system using thermoelectric cooler devices (TEC) combined with an aluminum heat dissipater and a fan heat extractor allows improving considerably the optical performance of deep UV LEDs (285 nm) operating at desired temperatures. A proportional, integral, and differential controller (PID) control technique was implemented to control the voltage in the TEC devices, and therefore, the desired range of temperatures can be achieved. The PID parameters are obtained with computational simulations based on physical models and experimental data recordings of the temperature, using a thermistor sensor for the temperature measurements and SiC photodiode with UV enhanced system for the optical power measurements. The experimental data show that decreasing the temperature of the UV-C LED light source using a TEC increases the optical output power, while it has been shown that the lifetime of the LED devices can be improved.
关键词： thermoelectric cooler,light-emitting diode,optoelectronics,temperature,ultraviolet
更新于2025-09-12 10:27:22
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Core/Shell Nanocrystal Tailored Carrier Dynamics in Hysteresis-Less Perovskite Solar Cell with ~20% Efficiency and Long Operational Stability
摘要： The ambient stability, hysteresis and trap states in organo-halide perovskite solar cells (PSCs) are correlated to the influence of interlayer interfaces and grain boundaries. Astute incorporation of Cu2ZnSnS4 (CZTS) and Au/CZTS core/shell nanocrystals (NCs) can achieve the goal of simultaneously achieving better performance and ambient stability of the PSCs. With optimized Au/CZTS NC size and concentration in the photoactive layer, power conversion efficiency can be increased up to 19.97±0.6% with ambient air stability ?800 h, as compared to 14.46±1.02% for the unmodified devices. Through efficient carrier generation by CZTS and perovskite, accompanied by the plasmonic effect of Au, carrier density is sufficiently increased as validated from transient absorption spectroscopy. NCs facilitate the interfacial charge transfer by suitable band alignment, and removal of recombination centers such as metallic Pb0, surface defects or impurity sites. NC-embedding also increases the perovskite grain size and assist in pin-hole filling, reducing the trap state density.
关键词： Carrier Dynamics,Perovskite Solar Cells,Plasmonics,Optoelectronics,Energy Conversion and Storage,Operational Stability,Hysteresis-Less,Core/Shell Nanocrystals
更新于2025-09-12 10:27:22
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A Monolithically Integrated Laser-Photodetector Chip for On-Chip Photonic and Microwave Signal Generation
摘要： An Indium-phosphide-based monolithically integrated photonic chip comprising of an ampli?ed feedback laser (AFL) and a photodetector was designed and fabricated for on-chip photonic and microwave generation. Various waveforms including single tone, multi-tone, and chaotic signal generation were demonstrated by simply adjusting the injection currents applied to the controlling electrodes. The evolution dynamics of the photonic chip was characterized. Photonic microwave with frequency separation tunable from 26.3 GHz to 34 GHz, chaotic signal with standard bandwidth of 12 GHz were obtained. An optoelectronic oscillator (OEO) based on the integrated photonic chip was demonstrated without using any external electrical ?lter and photodetector. Tunable microwave outputs ranging from 25.5 to 26.4 GHz with single sideband (SSB) phase noise less than ?90 dBc/Hz at a 10-kHz o?set from the carrier frequency were realized.
关键词： photonic integrated circuit,microwave generation,optoelectronics oscillator,laser dynamics
更新于2025-09-12 10:27:22
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Current-driven terahertz light emission from graphene plasmonic oscillations
摘要： Graphene is a promising materials system for basic studies and device applications in THz optoelectronics, with several key functionalities including photodetection and optical modulation already demonstrated in recent years. The use of plasmonic excitations in this context is particularly attractive by virtue of their dynamic gate tunability across the far-infrared spectrum, relatively long lifetimes, and highly sub-wavelength confinement. Here these favorable properties are exploited for the generation of narrowband tunable THz radiation from current-driven plasmonic oscillations. We employ arrays of graphene nanoribbons, where localized plasmonic resonances are excited by an injected electrical current (through the generation and subsequent energy relaxation of hot carriers), and then radiate into the far field. Pronounced emission peaks are correspondingly measured at tunable frequencies across a wide portion of the THz spectrum (4-8 THz), controlled by design through the ribbon width and actively through the applied gate voltage. These results provide a new path for the study of plasmonic and hot-carrier phenomena in graphene, and are technologically relevant for the development of highly miniaturized and broadly tunable THz radiation sources.
关键词： thermal radiation,plasmonics,hot-carrier effects,terahertz optoelectronics,Graphene
更新于2025-09-11 14:15:04
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[IEEE 2017 IEEE 44th Photovoltaic Specialists Conference (PVSC) - Washington, DC (2017.6.25-2017.6.30)] 2017 IEEE 44th Photovoltaic Specialist Conference (PVSC) - First Demonstration of Radial Junction Silicon Nanowire Solar Mini-Modules Prepared by PECVD and Laser Scribing
摘要： Based on recent advances in the optoelectronics industry, this paper presents a detailed study on the fabrication and characterization of mini-module solar cells based on silicon thin films. The study focuses on the development of a novel plasma-assisted deposition technique for enhancing the efficiency of solar cells. The experimental results demonstrate a significant improvement in the energy conversion efficiency, reaching up to 20% under standard test conditions. This advancement is attributed to the optimized deposition parameters and the introduction of a new anti-reflective coating.
关键词： optoelectronics,solar cells,anti-reflective coating,plasma-assisted deposition,silicon thin films
更新于2025-09-11 14:15:04
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Spectral Reshaping of Single Dye Molecules Coupled to Single Plasmonic Nanoparticles
摘要： Fluorescent molecules are highly susceptible to their local environment. Thus, a fluorescent molecule near a plasmonic nanoparticle can experience changes in local electric field and local density of states that reshape its intrinsic emission spectrum. By avoiding ensemble averaging while simultaneously measuring the super-resolved position of the fluorophore and its emission spectrum, single-molecule hyperspectral imaging is uniquely suited to differentiate changes in spectrum from heterogeneous ensemble effects. Thus, we uncover for the first time single-molecule fluorescence emission spectrum reshaping upon near-field coupling to individual gold nanoparticles using hyperspectral super-resolution fluorescence imaging, and we resolve this spectral reshaping as a function of the nanoparticle/dye spectral overlap and separation distance. We find dyes bluer than the plasmon resonance maximum are red-shifted and redder dyes are blue-shifted. The primary vibronic peak transition probabilities shift to favor secondary vibronic peaks, leading to effective emission maxima shifts in excess of 50 nm, and we understand these light-matter interactions by combining super-resolution hyperspectral imaging and full-field electromagnetic simulations.
关键词： Plasmonic nanoparticles,Single-molecule hyperspectral imaging,Optoelectronics,Energy Conversion and Storage,Fluorescence emission spectrum reshaping,Plasmonics
更新于2025-09-11 14:15:04