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Electrodeposition of photovoltaic thin films from ionic liquids in ambient atmosphere: Gallium from a chloroaluminate ionic liquid
摘要： At present time, semiconductive thin films used in photovoltaic cells can be successfully electrodeposited using ionic liquids in lab scale. However, scaling-up of this technology is hazardous due to the complexity involved to conduct electrodeposition in inert gas atmosphere. This paper reports on a novel approach for electrodeposition of gallium from a chloroaluminate ionic liquid composed of anhydrous aluminum chloride (AlCl3) and 1-ethyl-3-methylimidazolium chloride (EMIC) in ambient atmosphere, after protection with a non water-absorbable hydrocarbon layer. Cyclic voltammetry (CV) measurements were undertaken to characterize the electrodissolution and electrodeposition behavior of Ga. Potentiostatic electrodeposition experiments were conducted to deposit functional Ga layers on Pt, nickel, and mild steel substrates. SEM/EDX investigations revealed that Ga deposits have inhomogeneous microstructure developed through the progressive nucleation-growth mechanism that has been controlled by diffusion of Ga cations.
关键词： Ionic liquids,Semiconductors,Photovoltaic cells,Cyclic voltammetry,Electrodeposition,Gallium
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
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Sacrificial layer for laser lift-off process for flexible-display production
摘要： In this study, we developed a new sacrificial layer (SL) for laser transfer process. Metallic substrate i.e. invar foil was temporarily docked to a glass substrate using glass powder. To ensure successful delamination, the SL was pre-deposited between metal foil and glass substrate. For the first time, the SLs were amorphous gallium nitride and non-stoichiometric gallium oxide which were implemented for laser lift off (LLO) processes of metal foil. Bonding of metal foil to glass sheet was performed using heat treatment while debonding was achieved by LLO method. The laser wavelength was 355 nm which was the best fit for full absorption from SL layers. Transmission electron microscopy, element mapping, and energy dispersive X-ray spectroscopy analyses were performed for investigating elements’ migration and bonding-debonding mechanism.
关键词： Gallium oxide,Flexible displays,Gallium nitride,Laser lift-off,Sacrificial layer
更新于2025-09-11 14:15:04
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Microbial Approach to Low-Cost Production of Photovoltaic Nanomaterials
摘要： Photovoltaic (PV)-generated electricity can participate in renewable grid parity after meeting conditions of low-cost PV materials and economic manufacturing of solar cells. Here, we report low-cost, scalable microbial synthesis of Cu(In,Ga)Se2 (CIGSe) and Cu(In,Ga)S2 (CIGS), which are among the promising candidates to serve as light absorbing layers in solar panels. Microbial synthesis uses reducible chalcophiles and empirically stoichiometric metal components to produce CIGSe and CIGS with band gaps and intra- and intercrystallite compositional homogeneity similar to that produced with traditional techniques. Importantly, microbially produced photovoltaic materials described herein use inexpensive precursor materials at moderate temperatures (65 °C). The microbially facilitated processes do not utilize high temperature, vacuum, or toxic organic solvents. The potential to upscale microbial synthesis without loss of material quality is demonstrated here, indicating a high potential for industrial applications of this technology for production of nanomaterials for PV applications. We estimate that a 50 000 gallon fermentor could generate about 100 kg/month of CIGSe nanoparticles, which could be processed into 0.2 MW of PV cells.
关键词： inexpensive precursor materials,copper indium gallium selenide,Thermoanaerobacter,copper indium gallium sulfide,stoichiometric homogeneity
更新于2025-09-11 14:15:04
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Stronger Reductive Environment in Solvothermal Synthesis Leads to Improved Ga Doping Efficiency in ZnO Nanocrystals and Enhanced Plasmonic Absorption
摘要： The key parameter for degenerated semiconductor oxide plasmonic nanocrystals is the doping level. Hydrothermal and solvothermal approaches are considered to be less effective toward achieving high concentration of aliovalent donor dopants in a host oxide when compared to other synthesis methods that use long chain hydrocarbon solvents, fatty acids, and fatty amines as precursors. Because of this, although they have several advantages such as sustainability, ease of use, relatively inexpensive reagents and apparatus, and reduced environmental impact, they are excluded from the list of potential synthesis methods. Herein, an effective Zn2+ substitution with aliovalent Ga3+ in the ZnO host lattice is demonstrated, and it is achieved by increasing the reductive power of the solvothermal synthesis conditions by either solvent substitution or the addition of reducing agents. This increase results in an increased oxidation affinity of the medium. This in turn promotes Ga3+ incorporation into the ZnO lattice, by skewing the reaction equilibrium toward oxygen evolution.
关键词： plasmonic resonance,semiconductor nanocrystals,gallium-doped zinc oxide,degenerated oxide semiconductor nanocrystals
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Waikoloa Village, HI (2018.6.10-2018.6.15)] 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Opto-electrical Properties of GaN/Si Nanoheterostructure Array Device
摘要： A GaN/Si nanoheterostructure array was synthesized using the functional substrate of silicon nanoporous pillar array (Si-NPA) by CVD method. An n-GaN nanocolumnar/p-Si nanocrystalline nanoheterojuction array solar cell was fabricated and the GaN nanocolumnar grew along the [0001] direction. The device has an average integrated reflection of ~4.79% at the range of 300-1200 nm. The solar cell showed a Voc of 0.82 V, a Jsc of 23.21 mA, a FF of 38.3% and a maximum power conversion efficiency of 7.29%. The results provide a new conception of mass-nanoheterojuctions for photovoltaic filed.
关键词： Solar cells,Gallium nitride (GaN),Nanoheterostructure array,Silicon nanoporous pillar array (Si-NPA)
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Optically Driven Attosecond Electron Dynamics in III-V Semiconductors
摘要： A fundamental understanding of ultrafast electron dynamics in solids induced by light is of great interest for future high-speed electro-optical devices operating in the petahertz frequency regime. In the last years, a number of publications demonstrated the possibility to resolve and control carrier dynamics in semiconductors and dielectrics on the few- to sub-femtosecond time scale using attosecond transient absorption spectroscopy (ATAS). These experiments were performed with a non-resonant pump pulse, i.e. pump photon energies smaller than the corresponding band gap. Here in contrast, we resolve for the first time the attosecond carrier dynamics induced by a resonant intense laser pulse. We study the attosecond electronic response in gallium arsenide (GaAs), a technologically important narrow band gap semiconductor.
关键词： gallium arsenide,III-V semiconductors,attosecond transient absorption spectroscopy,ultrafast electron dynamics,attosecond electron dynamics
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Temperature Dependence of Magnetic Permeability and Optical Polarization Rotation of Gallium-Terbium Garnet Crystals
摘要： Faraday isolators (IF) are widely used in high-power fiber lasers in order to eliminate the detrimental influence of back reflections during the laser operation. One of the most widespread materials used for IF is a gallium-terbium garnet (TGG) crystal due to its appropriate magneto-optical properties. However, heating of magneto-optical crystals due to absorption of laser radiation deteriorates IF properties. Non-uniform heating leads to mechanical stresses and, therefore, to non-uniform polarization distortions. Values of optical absorption coefficients of TGG greatly depend on a crystal growth technology. Determination of the temperature dependence of optical absorption of TGG crystal was also one of the goals of this research. Optical absorption coefficient of cylindrical TGG sample (diameter d = 0.4 cm, length l = 2 cm) at 1060 nm wavelength was measured using laser calorimetry, i.e. by measuring the temperature of the crystal heated by transmitting laser radiation. Dependence of the crystal heating on transmitted optical power was 1.1±0.1 K/W. Absorption coefficient was calculated by solving the heat balance equation. Its value has increased from 1.6*10-3 cm-1 to 1.9*10-3 cm-1 as a result of heating from 22 oC to 43 oC. Also the contribution of the temperature dependent magnetic permeability μ(T) of TGG on the polarization rotation angle β was experimentally estimated. Temperature dependence of the magnetic permeability of TGG crystal was experimentally measured using resonant impedance spectroscopy. The value of TGG magnetic permeability was about 1.008 at room temperature (20 oC) and has decreased by Δμ = ? 1.2*10-4 when the crystal was heated to 80 oC. The temperature dependences of the polarization axis rotation angle change Δβ were measured in the cases of the uniform heating of TGG sample in a furnace and its nonuniform heating by transmitting linearly polarized laser radiation up to 30 W of optical power (1064 nm wavelength, 2 mm beam diameter). Applied magnetic field strength was 0,4 T, full angle of polarization axis rotation – 17,5 deg. Taking into account the measurement errors Δβ(T) ? (5 ± 0.25)*10-2 deg/ oC for both cases. It should be noticed that narrower laser beams can lead to greater differences due to the presence of larger temperature gradients. Consideration of the measurement results of μ(T) and β(T) revealed that the contribution of magnetic permeability variation with temperature to an overall polarization rotation angle change is almost 90 times lower than the thermally induced change of Verdet constant. Nevertheless, μ(T) influence should be considered if a precise control of polarization axis angle is required.
关键词： gallium-terbium garnet,Faraday isolators,TGG,magnetic permeability,temperature dependence,optical polarization rotation
更新于2025-09-11 14:15:04
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Effects of Zn <sup>2+</sup> and Ga <sup>3+</sup> doping on the quantum yield of cluster-derived InP quantum dots
摘要： As the commercial display market grows, the demand for low-toxicity, highly emissive, and size-tunable semiconducting nanoparticles has increased. Indium phosphide quantum dots represent a promising solution to these challenges; unfortunately, they typically suffer from low inherent emissivity resulting from charge carrier trapping. Strategies to improve the emissive characteristics of indium phosphide often involve zinc incorporation into or onto the core itself and the fabrication of core/shell heterostructures. InP clusters are high fidelity platforms for studying processes such as cation exchange and surface doping with exogenous ions since these clusters are used as single-source precursors for quantum dot synthesis. Here, we examined the incorporation of zinc and gallium ions in InP clusters and the use of the resultant doped clusters as single-source precursors to emissive heterostructured nanoparticles. Zinc ions were observed to readily react with InP clusters, resulting in partial cation exchange, whereas gallium resisted cluster incorporation. Zinc-doped clusters effectively converted to emissive nanoparticles, with quantum yields strongly correlated with zinc content. On the other hand, gallium-doped clusters failed to demonstrate improvements in quantum dot emission. These results indicate stark differences in the mechanisms associated with aliovalent and isovalent doping and provide insight into the use of doped clusters to make emissive quantum dots.
关键词： Indium phosphide,core/shell heterostructures,quantum yield,gallium doping,quantum dots,zinc doping
更新于2025-09-11 14:15:04
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An advanced approach to control the electro-optical properties of LT-GaAs-based terahertz photoconductive antenna
摘要： This work reports on an advanced approach to the design of THz photoconductive antenna (PCA). The LT-GaAs thin films used for the PCA fabrication were synthesized by MBE method on GaAs (100) substrate by adjusting the As pressure, As/Ga fluxes ratio, growth/annealing temperatures and annealing time. These parameters crucially affect electro-optical properties of the PCA samples as evidenced by the THz radiation power and time-domain spectroscopy measurements. The annealing temperature of 670 °C was found to be optimal for constructing a PCA possessing high amplitude of the THz radiation over the spectral range up to 1 THz at the resonance of 0.1 THz. The comparison of this PCA with the reference ZnTe crystal reveals a 2-fold increase in THz power. Furthermore, this antenna attains a 1.5-, 3-, and 2-fold increase in THz power, photocurrent efficiency, and actuating dc BV, as compared with the commercial ZOMEGA antenna. These results pave the way towards the creation of highly efficient LT-GaAs-based PCAs.
关键词： THz-antenna,Terahertz (THz) radiation,Photoconductive antenna (PCA),Low temperature-grown gallium arsenide (LT-GaAs),THz-spectroscopy
更新于2025-09-11 14:15:04