Ultraviolet photodetectors based on ZnO nanorods-seed layer effect and metal oxide modifying layer effect

Pt/ZnO nanorod (NR) and Pt/modified ZnO NR Schottky barrier ultraviolet (UV) photodetectors (PDs) were prepared with different seed layers and metal oxide modifying layer materials. In this paper, we discussed the effect of metal oxide modifying layer on the performance of UV PDs pre- and post-deposition annealing at 300°C, respectively. For Schottky barrier UV PDs with different seed layers, the MgZnO seed layer-PDs without metal oxide coating showed bigger responsivity and larger detectivity (Dλ*) than those of PDs with ZnO seed layer, and the reason was illustrated through energy band theory and the electron transport mechanism. Also the ratio of D254* to D546* was calculated above 8 × 102 for all PDs, which demonstrated that our PDs showed high selectivity for detecting UV light with less influence of light with long wavelength

Controllable synthesis of flake-like Al-doped ZnO nanostructures and its application in inverted organic solar cells

Flake-like Al-doped ZnO (AZO) nanostructures including dense AZO nanorods were obtained via a low-temperature (100°C) hydrothermal process. By doping and varying Al concentrations, the electrical conductivity (σ) and morphology of the AZO nanostructures can be readily controlled. The effect of σ and morphology of the AZO nanostructures on the performance of the inverted organic solar cells (IOSCs) was studied. It presents that the optimized power conversion efficiency of the AZO-based IOSCs is improved by approximately 58.7% compared with that of un-doped ZnO-based IOSCs. This is attributed to that the flake-like AZO nanostructures of high σ and tunable morphology not only provide a high-conduction pathway to facilitate electron transport but also lead to a large interfacial area for exciton dissociation and charge collection by electrodes

Ultraviolet photodetectors based on ZnO nanorods-seed layer effect and metal oxide modifying layer effect

<p>Abstract</p> <p>Pt/ZnO nanorod (NR) and Pt/modified ZnO NR Schottky barrier ultraviolet (UV) photodetectors (PDs) were prepared with different seed layers and metal oxide modifying layer materials. In this paper, we discussed the effect of metal oxide modifying layer on the performance of UV PDs pre- and post-deposition annealing at 300&#176;C, respectively. For Schottky barrier UV PDs with different seed layers, the MgZnO seed layer-PDs without metal oxide coating showed bigger responsivity and larger detectivity (<it>D</it>_&#955;*) than those of PDs with ZnO seed layer, and the reason was illustrated through energy band theory and the electron transport mechanism. Also the ratio of <it>D</it>₂₅₄* to <it>D</it>₅₄₆* was calculated above 8 &#215; 10²for all PDs, which demonstrated that our PDs showed high selectivity for detecting UV light with less influence of light with long wavelength.</p

A device with two kinds of functions —Ultraviolet photodetector and electroluminescence: Fabrication and carrier transport mechanism

We reported an n-ZnO/n-GaN heterojunction device in which both ultraviolet (UV) detecting and electroluminescence performances of the device are controlled by the applied forward-bias voltage. For ZnO-based UV photodetectors, our devices showed excellent photoresponse characteristics with detectivity of ∼2.80×1013 cm Hz1/2/W and responsivity of ∼276 A/W at 2 V. UV and visible electroluminescences of the device were also observed. Also, a Mn:ZnO/GaN heterojunction had been prepared and it also possessed the two functions. Furthermore, the Mn:ZnO/GaN device showed better UV detectivity and enlarged the visible emission. The reason for our devices possessing two functions had been explored through the carrier transport mechanism and the channel current formation diagram

Rational design of iron single atom anchored on nitrogen doped carbon as a high-performance electrocatalyst for all-solid-state flexible zinc-air batteries

Developing a cheap and high-efficiency oxygen reduction reaction (ORR) catalyst is vitally important for high-performance metal-air and full cell batteries. Non-noble iron-nitrogen-carbon materials (Fe-N-C) are reported with outstanding ORR property. However, most of them needs complex acid etching procedure during the fabrication process. Herein, we report a simple route to obtain a cost-effective Fe-N-C electrocatalyst via a facile two-step polymerization-pyrolysis process, and no acid etching is involved. Through a conjunction process of phthalocyanine iron (FePc) with polypyrrole (PPy) and a followed pyrolysis step, atomically evenly dispersed Fe-N-C species on nitrogen doped carbon can be easily obtained. Predictably, the obtained optimal catalyst delivers a half-wave potential of 0.83 V vs reversible hydrogen electrode (RHE) and better stability toward ORR test. Based on the optimal Fe single atomic catalyst as air cathode, an all-solid-state flexible Zn-air battery delivers a high open circuit voltage of 1.42 V, a high energy density of 833 Wh kg−1 and a high power density of 70 mW cm−2. The superior electrochemical energy storage properties demonstrated by the Fe-N-C electrocatalyst show a bright window for reasonable construction of cost-effective non-noble Fe single atom electrocatalysts for next-generation flexible energy storage devices.The work was supported by the Science and Technology Department of Hubei Province (No. 2019AAA020)

Metal–Organic Framework Template Derived Porous CoSe₂ Nanosheet Arrays for Energy Conversion and Storage

Porous CoSe₂ on carbon cloth is prepared from a cobalt-based metal organic framework template with etching and selenization reaction, which has both a larger specific surface area and outstanding electrical conductivity. As the catalyst for oxygen evolution reaction, the porous CoSe₂ achieves a lower onset potential of 1.48 V versus the reversible hydrogen electrode (RHE) and a small potential of 1.52 V (vs RHE) at an anodic current density of 10 mA cm^–2. Especially, the linear sweep voltammogram curve of the porous CoSe₂ is in consist with the initial curve after durability test for 24 h. When tested as an electrode for supercapacitor, it can deliver a specific capacitance of 713.9 F g^–1 at current density of 1 mA cm^–2 and exhibit excellent cycling stability in that a capacitance retention of 92.4% can be maintained after 5000 charge–discharge cycles at 5 mA cm^–2. Our work presents a novel strategy for construction of electrochemical electrode

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Structural and Optical Characterization of ZnO/Mg_<i>x</i>Zn_1–<i>x</i>O Multiple Quantum Wells Based Random Laser Diodes

Two kinds of laser diodes (LDs) comprised of ZnO/Mg_<i>x</i>Zn_1–<i>x</i>O (ZnO/MZO) multiple quantum wells (MQWs) grown on GaN (MQWs/GaN) and Si (MQWs/Si) substrates, respectively, have been constructed. The LD with MQWs/GaN exhibits ultraviolet random lasing under electrical excitation, while that with MQWs/Si does not. In the MQWs/Si, ZnO/MZO MQWs consist of nanoscaled crystallites, and the MZO layers undergo a phase separation of cubic MgO and hexagonal ZnO. Moreover, the Mg atom predominantly locates in the MZO layers along with a significant aggregation at the ZnO/MZO interfaces; in sharp contrast, the ZnO/MZO MQWs in the MQWs/GaN show a well-crystallized structure with epitaxial relationships among GaN, MZO, and ZnO. Notably, Mg is observed to diffuse into the ZnO well layers. The structure–optical property relationship of these two LDs is further discussed

High-Performance Photodetectors Based on Single All-Inorganic CsPbBr₃ Perovskite Microwire

In recent years, hybrid organic–inorganic perovskites have emerged as promising photosensing materials for next-generation solution-processed photodetectors, achieving high responsivity, fast speed, and large linear dynamic range. In particular, perovskite photoresistors possess low-cost fabrication and easy integration with low dimensional structures. However, a relatively large dark current is still limiting the further development of perovskite photoresistors. Herein, we introduce full-inorganic perovskite polycrystalline microwires for high-performance photodetection, in order to enhance the device stability. Furthermore, dark current and noise can be effectively suppressed by tuning the contacts. All-inorganic CsPbBr₃ microwires with a number of nanocrystals on the wire surface are prepared by a simple, low-cost, two-step, solution-processed method at room temperature. Photodetectors based on this CsPbBr₃ polycrystalline single microwire are assembled on indium tin oxide electrodes and demonstrate a decent responsivity up to 118 A/W and a fast response within 40 ms. In addition, such optimized photoresistors possess a fairly tiny dark current and noise, which result in an improved detectivity of >10¹² Jones and demonstrate excellent characteristics to detect weak light

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