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Design of lanthanide-based metal-organic frameworks with enhanced near-infrared emission
摘要： A strategy based on the use of ligand steric hindrance and metal doping is reported for the design and synthesis of near-infrared (NIR) emitting lanthanide-based metal–organic frameworks (MOFs). The lanthanide ions are free of coordinated solvents, and the resulting NIR-MOFs are highly emissive and exhibit long luminescence lifetimes.
关键词： metal doping,ligand steric hindrance,lanthanide-based metal–organic frameworks,luminescence,near-infrared emission
更新于2025-09-23 15:21:01
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Controlled doping of graphene by impurity charge compensation via a polarized ferroelectric polymer
摘要： A simple technique of doping graphene by manipulating adsorbed impurity charges is presented. Using a field effect transistor configuration, controlled polarization of a ferroelectric polymer gate is used to compensate and neutralize charges of one type. The uncompensated charges of the opposite type then dope graphene. Both n- and p-type doping are possible by this method, which is non-destructive and reversible. We observe a change in n-type dopant concentration of 8 × 1012 cm?2 and a change in electron mobility of 650%. The electron and hole mobilities are inversely proportional to the impurity concentration, as predicted by theory. Selective doping of graphene can be achieved using this method by patterning gate electrodes at strategic locations and programming them independently. Such charge control without introducing hard junctions, therefore, permits seamless integration of multiple devices on a continuous graphene film.
关键词： ferroelectric polymer,doping,graphene,charge compensation,field effect transistor
更新于2025-09-23 15:21:01
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Effects of Doping of Bragg Reflector Layers on the Electrical Characteristics of InGaAs/GaAs Metamorphic Photovoltaic Converters
摘要： The current–voltage characteristics of InxGa1 – xAs/GaAs metamorphic photovoltaic converters with built-in n-InGaAs/InAlAs Bragg reflectors are studied at an indium content of x = 0.025–0.24. The series resistance of the heterostructures is measured in the temperature range from 90 to 400 K. It is found that a sharp rise in the resistance of silicon-doped reflectors with an increasing fraction of In is due to weak activation of the donor impurity in InAlAs–n:Si layers. As a result, the energy barriers for majority carriers are formed in the latter, with a height of 0.32–0.36 eV and a substantial width. To suppress this effect, the technology of the Te doping of n-InGaAs/InAlAs Bragg reflectors is developed, which reduces the series resistance by five orders of magnitude. This makes it possible to keep the fill factor of the current–voltage characteristic above 80% up to current densities of 2 A/cm2. Values exceeding 85%, achieved for the quantum efficiency, indicate that the “memory” and tellurium segregation effects characteristic of this kind of impurity are suppressed.
关键词： InAlAs,resistive loss,doping,Bragg reflector,photovoltaic converter,heterointerface,InGaAs
更新于2025-09-23 15:21:01
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Minimizing Defect States in Lead Halide Perovskite Solar Cell Materials
摘要： In order to reach the theoretical e?ciency limits of lead-based metal halide perovskite solar cells, the voltage should be enhanced because it su?ers from non-radiative recombination. Perovskite materials contain intrinsic defects that can act as Shockley–Read–Hall recombination centers. Several experimental and computational studies have characterized such defect states within the band gap. We give a systematic overview of compositional engineering by distinguishing the di?erent defect-reducing mechanisms. Doping e?ects are divided into in?uences on: (1) crystallization; (2) lattice properties. Incorporation of dopant in?uences the lattice properties by: (a) lattice strain relaxation; (b) chemical bonding enhancement; (c) band gap tuning. The intrinsic lattice strain in undoped perovskite was shown to induce vacancy formation. The incorporation of smaller ions, such as Cl, F and Cd, increases the energy for vacancy formation. Zn doping is reported to induce strain relaxation but also to enhance the chemical bonding. The combination of computational studies using (DFT) calculations quantifying and qualifying the defect-reducing propensities of di?erent dopants with experimental studies is essential for a deeper understanding and unraveling insights, such as the dynamics of iodine vacancies and the photochemistry of the iodine interstitials, and can eventually lead to a more rational approach in the search for optimal photovoltaic materials.
关键词： semiconductor,solar energy,photovoltaics,doping,thin ?lm materials,voltage loss,stabilization,optimization,charge generation,light harvesting
更新于2025-09-23 15:21:01
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[IEEE 2020 IEEE 20th Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems (SiRF) - San Antonio, TX, USA (2020.1.26-2020.1.29)] 2020 IEEE 20th Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems (SiRF) - Progress Towards Fully On-Chip Frequency-Stabilization for Sub-Terahertz Sources
摘要： Resonators fabricated in heavily doped silicon have been noted to have a reduced frequency-temperature dependence compared with lightly doped silicon. The resonant frequency of silicon microelectromechanical systems (MEMS) resonators is largely governed by the material’s elastic properties, which are known to depend on doping. In this paper, a suite of different types and orientations of resonators were used to extract the ?rst- and second-order temperature dependences of the elastic constants of p-doped silicon up to 1.7e20 cm?3 and n-doped up to 6.6e19 cm?3. It is shown that these temperature-dependent elastic constants may be used in ?nite element analysis to predict the frequency-temperature dependence of similarly doped silicon resonators.
关键词： temperature dependence,Doping,resonators,silicon
更新于2025-09-23 15:21:01
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Performance Improvement of Gate-Tunable Organic Light-Emitting Diodes with Electron-Transport and Hole-Blocking Layers
摘要： The current density and luminance of gate-tunable organic light-emitting diodes (OLEDs) can be modulated by application of an external gate potential. However, existing gate-tunable OLEDs require further optimization to make them suitable for practical use. In this work, the rapid electron conduction of 4,4’-bis(N-carbazolyl)-1,1’biphenyl (CBP) molecules under low operating potential is demonstrated in polymer electrolyte-coated super yellow (SY) polymer light-emitting diodes (PLEDs). This behavior is attributed to the facile electrochemical n-doping of CBP by the polymer electrolyte infiltrated into the SY PLED through the porous aluminum cathode. The field-modulated conductivity of CBP upon applying an external gate potential to electrolyte-gated (EG) PLEDs is demonstrated. These phenomena lead to the improved performance of EG SY PLEDs with a CBP electron-transport layer and 1,3,5-tris[(3-pyridyl)-phen-3-yl]benzene) (TmpypB) hole-blocking layer between the porous aluminum cathode and SY emissive layer, including low turn-on voltage (1.5 V), low current density leakage (0.01 mA/cm2), low off luminance (<0.01 cd/m2), saturated on-current density (2 mA/cm2) and on-luminance (100 cd/m2), and largely suppressed hysteresis. These results pave the path for practical application of EG OLEDs in displays, especially near-to-eye displays.
关键词： facile electrochemical doping,saturated on-current density and on-luminance,low off-current density leakage and off-luminance,suppressed hysteresis,near-to-eye displays,gate-tunable organic light-emitting diodes,grayscale displaying,porous electrodes
更新于2025-09-23 15:21:01
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[IEEE 2019 Joint International EUROSOI Workshop and International Conference on Ultimate Integration on Silicon (EUROSOI-ULIS) - Grenoble, France (2019.4.1-2019.4.3)] 2019 Joint International EUROSOI Workshop and International Conference on Ultimate Integration on Silicon (EUROSOI-ULIS) - InAs Electron-Hole Bilayer LED
摘要： We report a novel switched-mode light-emitting device (LED) in an undoped ultra-thin body (UTB) InAs channel based on the electrostatically induced electron-hole (EH) bilayer concept. The induced EH channels at their respective gate interfaces, which remain spatially separated in steady state, gradually diffuse and recombine during a switch-off transient. Using TCAD simulations, we show that continuous switching of the gates with a ～ 12 μs time period leads to radiative recombination of the induced charge carriers with a peak internal quantum ef?ciency (IQE) as high as ～ 92%. The proposed concept obviates the need for chemically doped p-n junctions in the UTB device for light emitting applications and could also be employed for other direct bandgap semiconductors. However, the switching speed is ultimately limited by the thermal generation time.
关键词： ultra-thin body,thermal generation,light emission,Electrostatic doping,III-V on-insulator
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Room Temperature Wet Chemical Growth of an Oxygen Enhanced Diffusion Oxide Utilized in a Boron Diffusion Process
摘要： Resonators fabricated in heavily doped silicon have been noted to have a reduced frequency-temperature dependence compared with lightly doped silicon. The resonant frequency of silicon microelectromechanical systems (MEMS) resonators is largely governed by the material’s elastic properties, which are known to depend on doping. In this paper, a suite of different types and orientations of resonators were used to extract the ?rst- and second-order temperature dependences of the elastic constants of p-doped silicon up to 1.7e20 cm?3 and n-doped up to 6.6e19 cm?3. It is shown that these temperature-dependent elastic constants may be used in ?nite element analysis to predict the frequency-temperature dependence of similarly doped silicon resonators.
关键词： temperature dependence,Doping,resonators,silicon
更新于2025-09-23 15:21:01
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Strategies to Achieve High Performance Piezoelectric Nanogenerators
摘要： Piezoelectric nanogenerators have attracted much attention in the past decade. In this study, the development of piezoelectric nanogenerators and their progress toward high power generation is discussed. The characteristics and application range of numerous types of piezoelectric nanogenerators are also considered. In addition, several strategies that may improve the performance of piezoelectric nanogenerators are summarized. Here, we compare the open circuit voltages and short circuit currents of various piezoelectric nanogenerators under different factors, and the current problems of piezoelectric nanogenerators are also discussed. Finally, the future prospects and directions of piezoelectric nanogenerators are predicted. Future studies should be focused on the production of high-performance materials, the establishment of working principle and simulation model, the integration of nanogenerator, and the design of the energy harvesting circuit. Hence, it is emergency to search for functional materials with high piezoelectricity and further improve the electromechanical properties of existing piezoelectric materials. Moreover, further research is needed to increase the stability and flexibility of composite materials, to develop wearable and embedded flexible functional devices based on the biocompatibility of inorganic nanoparticles, and to supply power for microelectronic systems.
关键词： BaTiO3,Piezoelectric nanogenerators,Composite thin film materials,PVDF,Chemical doping,Nanostructure
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Room Temperature Synthesis of Lead-Free Sn/Ge-Based Perovskite Quantum Dots
摘要： Metal halide perovskites have received remarkable attention as photovoltaic (PV) devices. These have already achieved power conversion efficiency higher than 23% rivaling that of silicon-based PV. However, these outstanding efficiencies can only be acquired with lead-based perovskites and the devices are chemically unstable in air and moisture. Therefore, the key to the widespread deployment of perovskite-based solar cell will come down to address their “toxicity” and instability problems. We have taken the challenge to replace lead with other nontoxic or less toxic elements, e.g., Sn, and Ge. We have synthesized Cs(Sn,Ge)X3 (X=I, Br, and Cl) quantum dots (QDs) using room temperature process. The XRD data showed that the synthesized QDs were yellow hexagonal phase, which was further confirmed by the hexagonal shape of the TEM images of the crystals.
关键词： solar cell,nanoparticle,photoluminescence,doping,Lead-free perovskite
更新于2025-09-23 15:21:01