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- 2018
- Dual Material Gate (DMG)
- Vertical TFET
- Single Material Gate(SMG)
- Band-to-band tunneling (BTBT)
- Electronic Science and Technology
- National Institute of Technology Silchar
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Laser-induced forward transfer of soft material nanolayers with millisecond pulses shows contact-based material deposition
摘要： In this work, we present a qualitative and quantitative experimental analysis, as well as a numerical model, of a novel variant of the laser-induced forward transfer, which uses millisecond laser pulses. In this process, soft material nanolayer spots are transferred from a donor slide, which is coated with the soft material layer, to an acceptor slide via laser irradiation. This method offers a highly flexible material transfer to perform high-throughput combinatorial chemistry for the generation of biomolecule arrays. For the first time, we show visual evidence that the main transfer mechanism is contact-based, due to thermal surface expansion of the donor layer. Thus, the process is different from the many known variants of laser-induced forward transfer. We will characterize the maximum axial surface expansion in relation to laser power and pulse duration. On this basis, we derive a numerical model that approximates the axial surface expansion within measurement tolerances. Finally, we analyze the topology of the transferred soft material nanolayer spots by fluorescence imaging and vertical scanning interferometry to determine width, height, and shape of the transferred material. Concluding from this experimental and numerical data, we can now predict the amount of transferred material in this process.
关键词： high-speed imaging,fluorescence imaging,experimental and numerical prediction,vertical scanning interferometry,OpenFOAM
更新于2025-09-12 10:27:22
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Impact of Donor–Acceptor Interaction and Solvent Additive on the Vertical Composition Distribution of Bulk-Heterojunction Polymer Solar Cells
摘要： The vertical composition distribution of bulk-heterojunction (BHJ) photoactive layer is known to have dramatic effects on photovoltaic performance in polymer solar cells. However, the vertical composition distribution evolution rules of BHJ films are still elusive. In this contribution, three BHJ film systems, composed of polymer donor PBDB-T and three different classes of acceptor –fullerene acceptor PCBM, small molecule acceptor ITIC, and polymer acceptor N2200 –are systematically investigated using neutron reflectometry to examine how donor–acceptor interaction and solvent additive impact the vertical composition distribution. Our results show that those three BHJ films possess homogeneous vertical composition distributions across the bulk of the film. While very different composition accumulations near the top and bottom surface were observed which could be attributed to different repulsion, miscibility, and phase separation between the donor and acceptor components as approved by the measurement of donor–acceptor Flory–Huggins interaction parameter χ. Moreover, the solvent additive 1,8-diiodooctane (DIO) can induce more distinct vertical composition distribution especially in non-fullerene acceptor based BHJ films. Thus, higher power conversion efficiencies were achieved in inverted solar cells because of facilitated charge transport in active layer, improved carrier collection at electrodes, suppressed charge recombination in BHJ solar cells.
关键词： Flory–Huggins Interaction Parameter χ,Bulk-Heterojunction,Neutron Reflectometry,Polymer Solar Cells,Vertical Composition Distribution
更新于2025-09-12 10:27:22
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Potassium-Presenting Zinc Oxide Surfaces Induce Vertical Phase Separation in Fullerene-Free Organic Photovoltaics
摘要： Bulk heterojunction (BHJ) structure based organic photovoltaics (OPVs) have recently showed great potential for achieving high power conversion efficiencies (PCEs). An ideal BHJ structure would feature a large donor/acceptor interfacial area for efficient exciton dissociation and gradient distributions with high donor and acceptor concentrations near the anode and cathode, respectively, for efficient charge extraction. However, the random mixing of donor and acceptor in BHJ often suffers the severe charge recombination in the interface, resulting in poor charge extraction. Herein, we propose a new approach—treating the surface of the zinc oxide (ZnO) as electron transport layer with potassium hydroxide—to induce vertical phase separation of an active layer incorporating the non-fullerene acceptor IT-4F. Density functional theory calculations suggested that the binding energy difference between IT-4F and the PBDB-T-2Cl, to the potassium(K)-presenting ZnO interface is twice stronger than that for IT-4F and PBDB-T-2Cl to the untreated ZnO surface, such that it would induce more IT-4F moving toward the K-presenting ZnO interface than the untreated ZnO interface thermodynamically. Benefiting from efficient charge extraction, the best PCEs increased to 12.8% from 11.8% for PBDB-T-2Cl:IT-4F based devices, to 12.6% from 11.6% for PBDB-T-2Cl:Y1-4F based devices, to 13.5% from 12.2% for PBDB-T-2Cl:Y6 based devices, and to 15.7% from 15.1% for PM6:Y6 based devices.
关键词： DFT calculation,organic photovoltaics,potassium,vertical phase separation,non-fullerene acceptors
更新于2025-09-12 10:27:22
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A light salad [LED lighting applications in horticulture]
摘要： With their low energy usage, reduced heat output and the ability to control the light colour they emit, LEDs are poised to revolutionise the horticulture industry. This article explores the benefits of LED technology in vertical farming, including faster growth cycles, reduced water usage, and the elimination of pesticides. It also discusses the potential for custom-designed produce through controlled light exposure and the current economic challenges facing the adoption of LED technology in horticulture.
关键词： energy efficiency,LED,vertical farming,horticulture,controlled environment agriculture
更新于2025-09-12 10:27:22
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Monolithically Integrated GaN LED/Quasi-Vertical Power U-shaped Trench-gate MOSFET Pairs using Selective Epi Removal
摘要： We report on the demonstration of monolithically integrated light-emitting diode (LED) and quasi-vertical U-shaped trench-gate metal-oxide-semiconductor field-effect transistor (UMOSFET) in GaN. Selective epi removal (SER) approach was used on an LED-on-FET epi stack on sapphire substrates. Individual p-GaN layers were used for LED and FET in our design. LED light modulation by the supply voltage and the FET gate voltage was realized, and an integrated 350μm×350μm LED/UMOSFET pair exhibits a light output power (LOP) of 4.9 W/cm2 or 6.0 mW. An integrated device with a UMOSFET driving a 3-LED chain was also demonstrated. The normally-off power UMOSFET has a threshold voltage of 7 V, a breakdown voltage of 208 V, and a specific on-resistance of 23 mΩ-cm2, in which hexagonal cells were applied to obtain identical m-plane MOS gate interfaces. The effect of FET sizing on integrated pairs was also studied, and a trade-off model of FET/LED power ratio vs. FET/LED area ratio was created, which serves as universal criterion for FET/LED integration. The tested device with the best trade-off has FET/LED area ratio of 24% and FET/LED power ratio of 56%. This work creates a new building block for future GaN light-emitting integrated circuits (LEICs).
关键词： monolithic integration,FET/LED power ratio vs. area ratio trade-off,quasi-vertical power UMOSFET,LED,GaN
更新于2025-09-12 10:27:22
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[IEEE 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Ottawa, ON, Canada (2019.7.8-2019.7.12)] 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Electrical Properties of Oxide-Confined Vertical-Cavity Surface-Emitting Lasers
摘要： We present a comprehensive description of electrical properties of vertical-cavity surface-emitting lasers (VCSELs) based on a drift-diffusion model applied to carrier transport in 3D multilayer semiconductor laser heterostructure with a p-n junction. We address the impact of interface grading in distributed Bragg reflectors (DBRs), modulation doping of the DBRs and surrounding layers of the quantum well (QW) as well as material-dependent carrier mobilities and recombination constants and are focused on oxide-confined GaAs/AlGaAs VCSELs. We evaluate both depletion and diffusion capacitance and show that both contributions to the capacitance as well as the differential series resistance critically depend on the injection current and chip design such that, in general, VCSEL cannot be properly modeled by an equivalent circuit approximation. Current profiles demonstrate significant increase of the current density at the edges of the oxide-confined aperture (current crowding) which could be suppressed by a proper design.
关键词： current crowding,differential resistance,oxide aperture,carrier transport,capacitance,modulation frequency bandwidth,vertical cavity surface-emitting laser
更新于2025-09-12 10:27:22
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Photovoltaic systems with vertically mounted bifacial PV modules in combination with green roofs
摘要： Dependent on the specific conditions flat roofs can be well suited for the installation of large photovoltaic systems in urban areas. For urban designers also other aspects, such as the insulation of buildings, cooling, air purification and water retention play an important role besides the ecological energy generation. The combination of photovoltaics and roof greening can therefore be an interesting fusion. It combines the advantages of a green roof with the local electrical energy production at the place of consumption. However, using a conventional photovoltaic system with tilted modules in south or east-west direction on a green roof causes problems, as typical low tilt angels and high ground coverage rates result in an almost complete coverage of the roof surface. Plants, growing in between the covered areas provoke undesirable shading of the collector surface. Only a frequent maintenance procedure, complicated by dense PV system layouts, can avoid a reduction of the energy yield in the course of time. Vertically mounted specially designed bifacial modules are an option to realize photovoltaic power generation in combination with a functional green roof at low maintenance costs. In this paper, we report on the layout and the energy yield of a corresponding system. Custom-made bifacial modules with 20 cells were produced and vertically installed in landscape orientation. The narrow layout of the modules lowers the wind load and reduces the visibility. The enhanced power in the morning and evening of vertically east-west installed modules can additionally lead to higher self-consumptions rates. Despite having some shading and undergrounds with albedo factors of less than 0.2, the bifacial installation with a rated power of 9.09 kWp achieved a specific yield of the 942 kWh/kWp in one year (11.08.2017–10.08.2018). This is close to typical values of 1000 kWh/kWp achieved for south-facing PV systems in the same region. The impact of the greening on the albedo and the system performance is investigated in more detail with two smaller sub-systems. The energy yields of the two bifacial sub-systems are compared to a monofacial, south-facing reference module. The use of silver-leaved plants in this system resulted in higher albedo values and a more resilient roof greening.
关键词： PV system,Bifacial,Albedo,Urban areas,Vertical,Green roof
更新于2025-09-12 10:27:22
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Multiwavelength GaN‐Based Surface‐Emitting Lasers and Their Design Principles
摘要： Dual-wavelength lasing operations are demonstrated in GaN-based vertical-cavity surface-emitting lasers (VCSELs) comprising ingeniously designed asymmetric InGaN quantum wells (AS-QWs). The dual laser modes show exact positive-correlated polarization dependences with a high degree of polarization of up to 98%. By simply tuning the pump energy, the components and intensity of the laser outputs can be continuously changed, making wavelength selection and switching available for the GaN-based VCSELs. Detailed theoretical analysis and experimental measurements show that the intensity of optical gain and the coupling between the active layer and optical ?eld, namely the electron–photon interaction, as well as carrier tunneling and photon reabsorption play a crucial role in the multiwavelength lasing processes. Moreover, the design principles of the proposed AS-QWs and multistacked size-varied quantum dot (MS-QD) active regions are elaborated to provide guidelines for controllable multiwavelength emissions in GaN-based surface-emitting lasers. These results not only provide better understanding of lasing in nitride-based microcavity systems but also shed insight into the more fundamental issues of electron–photon coupling in such systems. Importantly, such controllable multiwavelength laser operations may extend nitride-based VCSELs to previously inaccessible areas, for example, ?ip-?op, ultrafast switches, and other functional devices such as Raman lasers and sensors.
关键词： vertical-cavity surface-emitting lasers,GaN,electron–photon interactions,multiwavelength lasers,design principles
更新于2025-09-12 10:27:22
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[IEEE 2019 International Workshop on Fiber Optics in Access Networks (FOAN) - Sarajevo, Bosnia and Herzegovina (2019.9.2-2019.9.4)] 2019 International Workshop on Fiber Optics in Access Networks (FOAN) - Studying and Simulation of a NS3 frameworktowards a 5G Complete Network Platform
摘要： In this paper, we present a novel NS3-based frameworkto simulate a complete 5G network architecture, including core, fronthaul andLTE access(i.e., Non-Standalone, 3GPP Release 15) radio access segments.Starting from the 5G Transformer model, we describe and simulate each single element of the three main functional plains. Some preliminary results are presented for a proposed algorithm for the QoS service orchestration controller.
关键词： 5G,LTE,C-RAN,Vertical Slice
更新于2025-09-12 10:27:22
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Integrable Quasi‐Vertical GaN UMOSFETs for Power and Optoelectronic ICs
摘要： Integrable, hexagonal-cell, high-voltage, quasi-vertical GaN power U-shaped trench-gate metal-oxide-semiconductor field-effect transistors (UMOSFETs) are experimentally demonstrated for the first time. Hexagonal cells are employed to obtain identical m-plane sidewalls for gate and drain trenches. Metallization compatible with LED optoelectronic integration is used. The dependence of device performance on different parameters is systematically studied and analyzed. The lowest Ron,sp of 23 mΩ-cm2 and highest drain saturation current of 295 A/cm2 were obtained by measuring an 11-μm cell-pitch UMOSFET. The breakdown voltage of an open-cell design variation (208 V) is higher than that of a closed-cell design variation (89 V), while the closed-cell design exhibits a lower off-state leakage current of 1.4×10-5 A/cm2. A hexagonal-cell specific on-state resistance Rcell,sp of 8.5 mΩ-cm2 and buried n+ layer sheet resistance RBL,□ of 223 Ω/□ are extracted by applying a two dimensional resistance network model to UMOSFETs of varying sizes.
关键词： hexagonal cell,array resistance network model,2D-gallium nitride,integrable quasi-vertical power UMOSFETs,gallium nitride
更新于2025-09-11 14:15:04