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Laser transmission welding and surface modification of graphene film for flexible supercapacitor applications
摘要： When a graphene ?lm is coated onto a ?exible polymer substrate, weak adhesion can cause delamination of the ?lm under mechanical bending. Moreover, as each graphene layer restacks, the performance of the ?lm as an electrode for a supercapacitor becomes limited. In this study, facile laser welding and surface modi?cation processes are demonstrated to overcome these limitations. First, a continuous wave laser beam is applied to the interface between the coated graphene and the underlying transparent polycarbonate substrate. This welding process signi?cantly improves their adhesion and enables excellent mechanical bendability. Second, surface modi?cation of graphene is achieved under ambient conditions by irradiating the graphene ?lm surface with a nanosecond pulsed laser. Sandwich-type supercapacitors are fabricated using these surface-modi?ed graphene electrodes with a PVA-H3PO4 electrolyte. The e?ect of the laser ?uence on the performance of the supercapacitor is investigated. At an optimal laser power, an areal capacitance of 4.7 mF/cm2 is achieved.
关键词： Laser transmission welding,Graphene,Flexible device,Supercapacitor,Pulsed laser
更新于2025-11-25 10:30:42
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La-doped p-type ZnO nanowire with enhanced piezoelectric performance for flexible nanogenerators
摘要： In recent years, energy harvesting has attracted considerable attention as a promising method to convert waste energy to useful energy. In particular, piezoelectric energy harvesters are of significant interest, because they have a simple structure and can be used to harvest energy regardless of weather or other environmental conditions. In accordance with the miniaturization trend of electronic devices driven by low power, piezoelectric nanogenerators (PENGs) using various nanostructured materials are being developed. Among them, ZnO nanowires (NWs) are most widely used for the use of PENGs. However, while research on n-type ZnO NWs is extensive, studies on p-type ZnO NWs are insufficient owing to their poor stability. In this study, La-doped p-type ZnO (La:ZnO) NWs were synthesized by a hydrothermal method to expand the applications of p-type ZnO and determine their potential as PENGs. XRD analysis showed that La3+ ions was well doped without the formation of any secondary phases and caused a change in the lattice parameter when compared to that of undoped ZnO. XPS analysis was performed to investigate the surface elemental compositions of La:ZnO NWs, and the morphology of La:ZnO NWs was investigated using SEM and TEM. We further studied the piezoelectric output performance of undoped and La-doped ZnO NWs, and found that La:ZnO NWs showed improved piezoelectric output performance as a result of electron screening effect of the p-type semiconductor.
关键词： p-type ZnO,La-doping,Flexible device,ZnO nanowires,Nanogenerators
更新于2025-09-23 15:23:52
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Flexible solar blind Ga2O3 ultraviolet photodetectors with high responsivity and photo-to-dark current ratio
摘要： In this work, flexible solar blind Ga2O3 ultraviolet photodetectors with high responsivity and photo-to-dark current ratio are demonstrated. The Ga2O3 films are obtained by the RF magnetron sputtering method on flexible polyimide (PI) substrates and the results demonstrate that all the films grown under various temperatures are amorphous. When the incident light wavelength is less than 254 nm, the incident light is effectively absorbed by the Ga2O3 film. By controlling the growth temperature of the material, the responsivity and photo-to-dark current ratio of the corresponding metal-semiconductor-metal photodetectors are significantly improved. At growth temperature of 200 oC, the current under 254 nm illumination obtains 396 nA at voltage of 20 V (corresponding responsivity is 52.6 A/W), the photo-to-dark current ratio is more than 105, and the external quantum efficiency reaches 2.6×10 4 %, which is among the best reported Ga2O3 ultraviolet photodetectors including the devices on the rigid substrates. After the bending and fatigue tests, the flexible detectors have negligible performance degradation, showing excellent mechanical and electrical stability.
关键词： solar blind photodetector,responsivity,photo-to-dark current ratio,Ga2O3,flexible device
更新于2025-09-19 17:13:59
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Molecular engineering of a conjugated polymer as a hole transporting layer for versatile p–i–n perovskite solar cells
摘要： Along with the development of perovskite materials, which have enormous potential for optoelectronics such as solar cells and light-emitting diode devices, numerous organic semiconductor polymers, which have been critically adopted into the hole and electron transporting layers, have been synthesized and studied. In neiep-structured perovskite solar cells, various outstanding polymer materials have been successfully applied. However, in peien-structured solar cells, the hydrophobic nature of the polymers makes the sequential deposition of a perovskite thin ?lm dif?cult. Several destructive methods have been proposed; however, a more ef?cacious and fundamental method is urgently needed. Here, we present a nondestructive polymer hole-transporting layer (HTL) thin-?lm formation process based on molecular engineering via a simple solvent process. When we used various solvents with different volatilities, perovskite ?lm formation was achieved on polymer thin ?lms formed from highly volatile solvents. In addition, we elucidated the structure and orientation of the molecules in the ?lms and revealed that the molecular structure of face-on orientation for the horizontally aligned hydrophobic alkyl groups induced a lower surface energy of the ?lm, as determined by grazing-incidence wide-angle X-ray scattering (GIWAXS) measurements. Furthermore, the tilt angle of the molecules, which was calculated from the results of quantitative near-edge X-ray absorption ?ne structure (NEXAFS) analysis, was found to correlate with the surface energy. This result provides guidance for polymer-orientation and surface-energy studies, and perovskite solar cells fabricated using the polymer HTL demonstrated good durability and ?exibility. We expect that our approach represents a new route for fabricating peien-structured solar cells and that numerous valuable p-type conjugated polymers will be developed via our proposed molecular engineering process.
关键词： Solvent process,Organic semiconductor,Flexible device,Conjugated polymer,Perovskite solar cell,Molecular engineering
更新于2025-09-19 17:13:59
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Demonstration of Solar Cell on a Graphite Sheet with Carbon Diffusion Barrier Evaluation
摘要： An amorphous Si (a-Si) solar cell with a back reflector composed of zinc oxide (ZnO) and silver (Ag) is potentially the most plausible and flexible solar cell if a graphite sheet is used as the substrate. Graphite supplies lightness, conductivity and flexibility to devices. When a graphite sheet is used as the substrate, carbon can diffuse into the Ag layer in the subsequent p-i-n process at 200–400 °C. To prevent this, we added an oxide layer as a carbon diffusion barrier between the carbon substrate and the back reflector. For the carbon diffusion barrier, silicon oxide (SiO2) or tin oxide (SnOx) was used. We evaluated the thermal stability of the back reflector of a carbon substrate using secondary-ion mass spectrometry (SIMS) to analyze the carbon diffusion barrier material. We confirmed the deposition characteristics, reflectance and prevention of carbon diffusion with and without the barrier. Finally, the structures were incorporated into the solar cell and their performances compared. The results showed that the back reflectors that were connected to a carbon diffusion barrier presented better performance, and the reflector with an SnOx layer presented the best performance.
关键词： flexible device,carbon diffusion barrier,a-Si solar cell,carbon substrate,graphite sheet
更新于2025-09-16 10:30:52
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ZnO@graphene QDs with tuned surface functionalities formed on eco-friendly keratin nanofiber textile for transparent and flexible ultraviolet photodetectors
摘要： We demonstrate the ZnO@graphene core@shell quantum dot (ZGQDs) fabricated by selectively engineering of oxygenated functional groups on the graphene shells with eco-friendly keratin textile for transparent and flexible UV photodetector devices. The ZGQDs with the octylamine (ZGQDs-OA) and the graphene sheet were employed as an active material and an electron transport channel. The functional groups on the surrounding graphene shell in ZGQDs were passivated by the OA, resulting in a good absorbance in UV light and excellent carrier transport properties. The passivation of the functional groups on the graphene shell by OA drastically enhanced the photocurrent. Optical transmittance of the ZGQDs-OA/graphene sheets/PMMA/keratin nanofiber textile composites structures was approximately 77 % at the visible spectrum range. Current–voltage (I-V) and current–time (I-t) measurements on the UV photodetector under illumination state in bending condition exhibited the excellent ON/OFF switching states and stability. The photosensitivity and responsivity of the photodetector with ZGQDs-OA were found to be around 13.10 and 68.64 μAmW-1, respectively, which is much higher than that without the passivation. The improved performance of the photodetector with ZGQDs-OA could be attributed to the efficient electron transport to the electrode by the passivation of the graphene on ZnO QDs.
关键词： ZnO@graphene QDs,flexible device,photodetector,Eco-friendly,Textile
更新于2025-09-12 10:27:22
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Flexible piezoelectric ultrasonic energy harvester array for bio-implantable wireless generator
摘要： Ultrasonic driven wireless charging technology has recently attracted much attention in the next generation bio-implantable systems; however, most developed ultrasonic energy harvesters are bulky and rigid and cannot be applied to general complex surfaces. Here, a flexible piezoelectric ultrasonic energy harvester (PUEH) array was designed and fabricated by integrating a large number of piezoelectric active elements with multilayered flexible electrodes in an elastomer membrane. The developed flexible PUEH device can be driven by the ultrasonic wave to produce continuous voltage and current outputs on both planar and curved surfaces, reaching output signals of more than 2 Vpp and 4 μA, respectively. Potential applications of using the flexible PUEH to charge energy-storage devices and power commercial electronics were demonstrated. Its low attenuation performance was also evaluated using the in vitro test of transmitting power through pork tissue, demonstrating its potential use in the next generation of wirelessly powered bio-implantable micro-devices.
关键词： piezoelectric,ultrasonic energy harvester,wireless generator.,flexible device
更新于2025-09-10 09:29:36
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All solution-based heterogeneous material formation for p-n junction diodes
摘要： All solution-based devices have potential as the next class of macroscale and multifunctional electronics on versatile amorphous substrates. Different methods and materials have been studied to control the formation of p-type and n-type semiconducting materials because forming active materials for transistors and sensors remains challenge. This study proposes an approach for solution-based devices in which a p-n junction diode is fabricated using a solution-based InZnO (IZO) thin film for the n-type semiconductor and a carbon nanotube (CNT) network film for the p-type semiconductor. Additionally, the barrier height (~160 meV) is extracted and a p-n junction diode on a plastic film is demonstrated. Although the performance requires further improvements by modifying the interfaces, this printing method may be an interesting approach for all-printed electronics, which can replace conventional Si electronics.
关键词： flexible device,hetero-junction,diode,InZnO,carbon nanotube
更新于2025-09-10 09:29:36
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Microdroplet electrowetting actuation on flexible paper-based lab on a chip
摘要： This paper presents the microdroplets electrowetting causing by the voltage actuation on the ?exible lab on a chip. The electrode is made of a thin Aluminium (Al) ?lm while the lab on a chip substrate is made from the cellulose paper, which is ?exible. Consistently in this work the microdroplet samples of 5 μl from Potassium Chloride (KCl) is experimented on top of the electrodes. It is shown that the ?exible paper-based lab on a EW chip has ful?lled the Lippmann’s equation where the higher the voltage supply, the lesser the interfacial tension of droplet. Moreover, the droplet has e?ciently trailed along the track of activated electrodes when using the olive oil as the dielectric layer. The olive oil with dielectric permittivity of 3.2 has given the best displacement and high velocity of the droplet transportation. The best low voltage to move the microdroplet between the two planar electrodes is 12 Vpp under the frequency of 10 Hz.
关键词： Paper-based chip,Flexible device,Aluminium electrode,Electrowetting,Microdroplet
更新于2025-09-09 09:28:46