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

In situ TEM observation of crystal structure transformation in InAs nanowires on atomic scale

In situ transmission electron microscopy investigation of structural transformation in III-V nanowires is essential for providing direct insight into the structural stability of III-V nanowires under elevated temperature. In this study, through in situ heating investigation in a transmission electron microscope, the detailed structural transformation of InAs nanowires from wurtzite structure to zinc-blende structure at the catalyst/nanowire interface is witnessed on the atomic level. Through detailed structural and dynamic analysis, it was found that the nucleation site of each new layer of InAs and catalyst surface energy play a decisive role in the growth of the zinc-blende structure. This study provides new insights into the growth mechanism of zinc-blende-structured III-V nanowires

MXene‐enhanced environmentally stable organohydrogel ionic diode toward harvesting ultralow‐frequency mechanical energy and moisture energy

Abstract With the accelerating advancement of distributed sensors and portable electronic devices in the era of big data, harvesting energy from the surrounding environment to power electrical devices has become increasingly attractive. However, most mechanical energy harvesters often require high operating frequencies to function properly. Moreover, for practical applications, the survivability of devices in harsh operating environments is a vital issue which must be addressed. Besides, the single‐stimulus responsiveness limits their further applications in complex external environments. Here, a pressure and moisture dual‐responsive ionic diode consisting of two organohydrogels with opposite charges as an energy harvester is proposed. The organohydrogel ionic diode utilizes the migration of cations and anions to form the depletion zone and followed by an enhancement of the built‐in potential along the depletion zone as a result of mechanical stress or humidity, converting ultralow‐frequency mechanical energy or moisture energy into electrical energy. Meanwhile, this mechanism is further confirmed by the finite element analysis. With the increased rectification ratio due to the introduction of MXene, the ionic diode exhibits a relatively large output current (∼10.10 μA cm−2) and power density (∼0.10 μW cm−2) at a mechanical pressure of 0.01 Hz, outperforming most currently available mechanical energy harvesters. More impressively, the incorporation of ethylene glycol provides the hydrogel ionic diode with excellent temperature tolerance and long‐term environmental stability. The organohydrogel ionic diode can also be applied as a moisture‐driven power generator and self‐powered humidity sensor. This study presents promising prospects for the efficient collection of renewable and sustainable energy and the practical application of hydrogel‐based energy harvesters in extreme environments

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

<p>Abstract</p> <p>Flake-like Al-doped ZnO (AZO) nanostructures including dense AZO nanorods were obtained via a low-temperature (100&#176;C) hydrothermal process. By doping and varying Al concentrations, the electrical conductivity (<it>&#963;</it>) and morphology of the AZO nanostructures can be readily controlled. The effect of <it>&#963; </it>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 &#963; 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.</p

Highly Stretchable and Self-Healable Supercapacitor with Reduced Graphene Oxide Based Fiber Springs

In large-scale applications of portable and wearable electronic devices, high-performance supercapacitors are important energy supply sources. However, since the reliability and stability of supercapacitors are generally destroyed by mechanical deformation and damage during practical applications, the stretchability and self-healability must be exploited for the supercapacitors. Preparing the highly stretchable and self-healable electrodes is still a challenge. Here, we report reduced graphene oxide fiber based springs as electrodes for stretchable and self-healable supercapacitors. The fiber springs (diameters of 295 μm) are thick enough to reconnect the broken electrodes accurately by visual inspection. By wrapping fiber springs with a self-healing polymer outer shell, a stretchable and self-healable supercapacitor is successfully realized. The supercapacitor has 82.4% capacitance retention after a large stretch (100%), and 54.2% capacitance retention after the third healing. This work gave an essential strategy for designing and fabricating stretchable and self-healable supercapacitors in next-generation multifunctional electronic devices