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Current Spreading Length and Injection Efficiency in ZnO/GaN-Based Light-Emitting Diodes
摘要： We report on carrier injection features in light-emitting diodes (LEDs) based on nonintentionally doped-ZnO/p-GaN heterostructures. These LEDs consist of a ZnO layer grown by chemical-bath deposition (CBD) onto a p-GaN template without using any seed layer. The ZnO layer (～1-μm thickness) consists of a dense collection of partially coalesced ZnO nanorods, organized in wurtzite phase with marked vertical orientation, whose density depends on the concentration of the solution during the CBD process. Due to the limited conductivity of the p-GaN layer, the recombination in the n-region is strongly dependent on the spreading length of the holes, Lh, coming from the p-contact. Moreover, the evaluation of Lh is not easy and generally requires the design and the fabrication of several LED test patterns. We propose a simple and effective method to calculate Lh, just based on simple considerations on I–V characteristics, and a way to improve the injection efficiency in the n region based on a noncircular electrode geometry. In particular, an interdigitated electrode structure is proved to be more efficient in terms of hole injection from n- to p-region.
关键词： zinc oxide (ZnO) nanorods,ZnO/GaN heterostructures,ZnO/GaN-based light-emitting diodes (LEDs),contact injection,current spreading length,Chemical-bath deposition (CBD)
更新于2025-09-16 10:30:52
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Enhanced photoresponse in ZnO nanorod array/p-GaN self-powered ultraviolet photodetectors via coupling with CuO nanostructures
摘要： ZnO nanorod arrays (ZnO NRAs) coupled with coral-like CuO nanostructures (CuO CLNs) were prepared by low-temperature hydrothermal method. Self-powered ultraviolet (UV) photodetectors (PDs) based on ZnO NRAs/CuO CLNs/p-GaN heterostructure were fabricated via a direct-contact method. Under UV illumination (1.46 mW cm?2), the ratios of photocurrent to dark current (Iphoto/Idark), photo-responsivity and speci?c detectivity for the ZnO NRAs/CuO CLNs/p-GaN heterojunction self-powered PD were estimated to be 1143, 1.44 mA W?1 and 5.9×1010 cm Hz1/2/W at 0 V, which were about ～187, ～104 and ～153 times greater than those of the ZnO NRAs/p-GaN self-powered PD, respectively. Moreover, the PD displayed faster response time, excellent stability and repeatability by coupling with CuO CLNs. The mechanism of the enhanced photoresponse performance was discussed through the energy band diagram.
关键词： self-powered,CuO nanostructures,ultraviolet photodetector,ZnO nanorods
更新于2025-09-16 10:30:52
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Inserting dome shape microstructure for enhancement of ultraviolet photodetector performance of n-ZnO nanorods/p-Si heterojunction
摘要： A mixed intermediate layer of silica and zinc oxide (SZO) with architecturally dome-shaped microstructure is fabricated and characterized by combining a hydrothermal method and a plasma-enhanced chemical vapor deposition technique. Our results demonstrated that 200 (cid:1)C was an optimum deposition temperature for dome shape architecture SZO layer, acting as an antire?ection layer in the ultraviolet range and buffer layer for growth ZnO nanorods (NRs) arrays. Consequently, at 2.0 V reverse bias, the photo-to-dark current ratio measured with an p-Si/n-ZnONRs photodiode employing the dome-shaped SZO layer is improved by almost three orders of magnitude in the ultraviolet range as compared to that under visible-light illumination.
关键词： ZnO nanorods,Hydrothermal growth,Plasma-enhanced chemical vapor deposition,Photodiodes
更新于2025-09-16 10:30:52
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Natural Dyes Extracted from Fruits of Phyllanthus reticulatus as Sensitizers in ZnO Nanorods Based Dye Sensitized Solar Cells
摘要： DSSCs are a promising class of photovoltaic cells with the capability of generating green energy at low production cost since no expensive equipment is required in their fabrication. Zinc oxide (ZnO) nanorods were synthesized by hydrothermal method and their perfomance as photoanodes in dye-sensitized solar cells (DSSCs) employing I-/I3- as electrolyte and the dye extracts from fruits of Phyllanthus reticulatus as sensitizers was analyzed. the structural and surface characterization of the ZnO nanorods were accomplished using X- ray diffraction (XRD) analysis and high resolution scanning electron microscopy (HRSEM). XRD results revealed that the synthesized ZnO material exhibited hexagonal crystal structure which was found to be highly stable and crystallite. The dielectric properties of the ZnO nanorods were analyzed. The dye extracts were subjected to UV-Visible absorption spectroscopy analysis. The short-circuit photocurrent, the open-circuit photovoltage, and the power conversion efficiency of DSSC were measured using J-V measurement system.
关键词： Phyllanthus reticulatus,DSSC,XRD,HRSEM,ZnO nanorods
更新于2025-09-16 10:30:52
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ZnO nanorods array as light absorption antenna for high-gain UV photodetectors
摘要： Hydrothermal method provides the advantages of simple, low-temperature growth conditions, low cost and large surface areas for the samples. Also, exciton dissociation can be enhanced by surface plasmon resonance (SPR) due to the plasmonic absorption enhancement of incident light. In this paper, high-gain ultraviolet (UV) photodetectors based on vertically aligned ZnO nanorods (ZnO-NRs) array as light absorption antenna were presented, in which ZnO-NRs array was prepared by hydrothermal method. Our experimental data showed that the device performance of the UV photodetector Au/ZnO(ZnO-NRs:Au-NPs)/Au can be further enhanced after the gaps of ZnO-NRs array were filled with Au nanoparticles (Au-NPs). The photo-to-dark current ratio and the specific detectivity of the UV photodetector Au/ZnO(ZnO-NRs:Au-NPs)/Au reached to 1×105 and 1.84×1013 Jones at 2 V under 100 μW/cm2 365 nm illumination, respectively. The physical mechanism for the enhanced performance of the UV photodetectors is discussed.
关键词： Surface plasmon resonance (SPR),ZnO nanorods (ZnO-NRs) array,Ultraviolet (UV) photodetectors,Hydrothermal method,Schottky contact
更新于2025-09-12 10:27:22
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Three-dimensional ZnO nanorods growth on ZnO nanorods seed layer for high responsivity UV photodetector
摘要： Three-dimensional ZnO nanorods (NRs) were synthesized by hydrothermal method on ZnO seed layer including horizontal ZnO NRs. The ZnO seed layers consist of different values of NRs were synthesized by spin-coating. The different seed layers and ZnO nanorods arrays were characterized using field emission scanning electron microscopy, X-ray diffraction. Horizontally dispersed NRs on the substrate formed an overlapping junction structure into seed layer as ZnO NRs network. NRs grown on the seed layer including horizontal NRs were oriented in different directions to form three-dimensional ZnO NRs in flower shape. The electrical resistance of sensors based NRs array decreased dramatically with increasing NRs added to ZnO seed layer. Results show that ultraviolet photocurrent increased from 1.7 to 23 μA which is suitable for fabrication of practical photodevices.
关键词： UV photodetector,ZnO nanorods,seed layer,photocurrent,hydrothermal method
更新于2025-09-12 10:27:22
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Effects of precursor concentration on hydrothermally grown ZnO nanorods as electron transporting layer in perovskite solar cells
摘要： Electron transporting later (ETL) with nanorod structure provides a special passage for which free electrons can easily travel through the layer. ETL also helps to prevent the recombination and to enhance the attaching ability of the perovskite layer and thus improving the conversion efficiency of the perovskite solar cell. In this work, the investigation on the hydrothermal process of n-type ZnO nanorods (ZnO NRs) layer is carried out at the temperature below 100 oC and under the atmospheric pressure. Four concentrations of aqueous precursor solution consisting of zinc nitrate hexahydrate and hexamethylenetetramine are used in the experiment (25 mM, 50 mM, 75 mM and 100 mM). Subsequently, the perovskite solar cells, with normal structure of FTO- glass/ZnO dense layer/ZnO NRs/PCBM/Perovskite/P3HT/Ag, are fabricated. The optimum power conversion efficiency of 2.26% was obtained from the device prepared with 100 mM precursor solution. The concentration of solution used in the hydrothermal process affects the size and density of ZnO NRs and, in turn, affects the conversion efficiency of the cells.
关键词： concentrations,hydrothermal process,normal structure,perovskite solar cells,ZnO nanorods
更新于2025-09-12 10:27:22
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ZnO@TiO2 Core Shell Nanorod Arrays with Tailored Structural, Electrical, and Optical Properties for Photovoltaic Application
摘要： ZnO has prominent electron transport and optical properties, beneficial for photovoltaic application, but its surface is prone to the formation of defects. To overcome this problem, we deposited nanostructured TiO2 thin film on ZnO nanorods to form a stable shell. ZnO nanorods synthesized by wet-chemistry are single crystals. Three different procedures for deposition of TiO2 were applied. The influence of preparation methods and parameters on the structure, morphology, electrical and optical properties were studied. Nanostructured TiO2 shells show different morphologies dependent on deposition methods: (1) separated nanoparticles (by pulsed laser deposition (PLD) in Ar), (2) a layer with nonhomogeneous thickness (by PLD in vacuum or DC reactive magnetron sputtering), and (3) a homogenous thin layer along the nanorods (by chemical deposition). Based on the structural study, we chose the preparation parameters to obtain an anatase structure of the TiO2 shell. Impedance spectroscopy shows pure electron conductivity that was considerably better in all the ZnO@TiO2 than in bare ZnO nanorods or TiO2 layers. The best conductivity among the studied samples and the lowest activation energy was observed for the sample with a chemically deposited TiO2 shell. Higher transparency in the visible part of spectrum was achieved for the sample with a homogenous TiO2 layer along the nanorods, then in the samples with a layer of varying thickness.
关键词： TiO2 thin film,optical properties,ZnO nanorods,chemical deposition,DC reactive magnetron sputtering,pulsed laser deposition,electrical properties,core–shell
更新于2025-09-12 10:27:22
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p-GaN/n-ZnO Nanorod/CsPbBr <sub/>3</sub> Quantum Dots Decorated with ZnO Nanoseeds for Light-Emitting Diodes
摘要： In this paper, we report the dual-wavelength green-light emission from zinc oxide (ZnO)-nanoseed-decorated p-GaN (gallium nitride)/n-ZnO nanorod/CsPbBr3 quantum dots (QDs) light-emitting diodes (LEDs). At the same time, the effect of ZnO nanoseeds on the p-GaN/n-ZnO nanorod/CsPbBr3 QDs LED performance is deeply studied. ZnO nanoseeds were fabricated by magnetron sputtering and the sol?gel method; then ZnO nanorods were obtained on GaN by hydrothermal treatment to form the p-GaN/n-ZnO nanorod heterojunction, and green CsPbBr3 QDs were further deposited on ZnO nanorod arrays to realize LEDs. The results show that magnetron-sputtering ZnO nanoseeds can induce regular vertical ZnO nanorod arrays, and the corresponding device presents a better electroluminescence (EL) performance. The X-ray diffraction, atomic force microscopy, and EL mechanisms indicate that the p-GaN/n-ZnO nanorod with magnetron-sputtering ZnO nanoseeds has a better crystalline interface. Our results indicate that the p-GaN/n-ZnO nanorod/CsPbBr3 QDs heterojunction structure can be served as dual-wavelength LEDs, and magnetron-sputtering ZnO nanoseeds can give rise to a better EL performance.
关键词： CsPbBr3 quantum dots,electroluminescence,ZnO nanoseeds,ZnO nanorods,light-emitting diodes
更新于2025-09-11 14:15:04
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The effect of indium doping on photovoltaic properties of chemically synthesized zinc oxide thin-film electrodes
摘要： Photovoltaic (PV) performance of chemically synthesized indium-doped zinc oxide (IZO) nanorod electrodes has been investigated by photocurrent density-voltage (J-V). The indium (In) concentration was varied from 2 to 6 at.% for IZO. The J-V measurements as performed under a dark condition and a simulated white light of 80 mW/cm2 confirmed increase in PV performance with the IZO electrodes, making a peak with the 4 at.% In concentration. The investigated properties of the synthesized In-doped ZnO nanorod electrodes (structural and optical) strongly agreed with the PV results and well support the enhanced PV performance of the IZO electrodes. This clearly indicates that IZO electrodes would be preferred against undoped ones in PV solar cell application.
关键词： IZO electrodes,Photovoltaic performance,In concentration,Wurtzite crystal structure,ZnO nanorods
更新于2025-09-11 14:15:04