Charge Storage Elements Research Articles

EICO: Energy-Harvesting Long-Range Environmental Sensor Nodes With Energy-Information Dynamic Co-Optimization

Intensive research on energy-harvested sensor nodes has been driven by the challenges in achieving stringent design goals of battery lifetime, information accuracy, transmission distance, and cost. This challenge is further amplified by the inherent power-intensive nature of long-range communication when sensor networks are required to span vast areas, such as agricultural fields and remote terrain. Solar power is a common energy source in wireless sensor nodes, however, it is not reliable due to fluctuations in available power stemming from the changing seasons and weather conditions. This article tackles these issues by presenting a perpetually powered, energy-harvesting sensor node which utilizes a minimally sized solar cell and is capable of long-range communication by dynamically co-optimizing energy consumption and information transfer, termed as energy-information dynamic co-optimization (EICO). This energy-information intelligence is achieved by adaptive dutycycling of information transfer based on the total amount of energy available from the harvester and charge storage element to optimize the energy consumption of the sensor node, while employing in-sensor analytics (ISA) to minimize loss of information. This is the first reported sensor node < 35 cm2 in dimension, which is capable of long-range communication over >1 km at continuous information transfer rates of up to 1 packet/second which is enabled by EICO and ISA.

Multi-objective optimal energy management of storage system and distributed generations via water cycle algorithm concerning renewable resources uncertainties and pollution reduction

This paper intends to analyze micro-grid energy management optimally with consideration of renewable resources, and taking into account the objectives such as pollution decrease and uncertainty, as well as economic objective. Accordingly, the micro-grid has been optimized with assumption of resources like solar and wind energy, and the use of fuel cells, micro turbines and storage batteries with the purpose of minimization of energy consumption price accompanied by reduction of the amounts of emitted pollutants in a micro-grid. The optimization process aims to determine how to charge and discharge storage elements by considering the type of load, and to determine the amount of micro turbine production, and fuel cell usage, as well as energy exchange with the upstream network according to the daily energy price. In this study, water cycle algorithm (WCA) utilization for energy consumption smart optimization has been considered, and besides, the use of probabilistic scenarios intended for modeling the renewable resources and the load uncertainty has been taken into account. From the derived results, it can be concluded that, once economic objective is considered, the optimizer effort is to deliver the load at the minimum cost, leading to increments in the pollution emission in this case. On the other hand, in the case of considering the emission function merely, the reverse will occur. If the mentioned functions are considered concurrently, a balance can be detected between in-network production and the upstream grid received energy with the aim of maintaining the pollutants emission and the costs at a reasonable amount. As a final point, the results derived from the presented method are analyzed against the operation costs of the micro-grid, acquired via mixed-integer linear programming(MILP), genetic algorithm(GA), and particle swarm optimization(PSO), authenticating the scheme precision.

Iodide Electrolyte-Based Hybrid Supercapacitor for Compact Photo-Rechargeable Energy Storage System Utilising Silicon Solar Cells

The one of the most important issues in constructing light-harvesting photovoltaic (PV) systems with a charge storage element is its reliable and uninterrupted use in highly variable and weather-dependent conditions in everyday applications. Herein, we report the construction and applicability evaluation of a ready-to-use portable solar charger comprising a silicon solar cell and an enhanced energy hybrid supercapacitor using activated carbon electrodes and iodide-based aqueous electrolyte to stabilise the PV power under fluctuating light conditions. The optimised electrode/electrolyte combination of a supercapacitor was used for the construction of a 60 F/3 V module by a proper adjustment of the series and parallel connections between the CR2032 coin cells. The final photo-rechargeable device was tested as a potential supporting system for pulse electronic applications under various laboratory conditions (temperature of 15 and 25 °C, solar irradiation of 600 and 1000 W m−2).

Ruddlesden-Popper-Phase Hybrid Halide Perovskite/Small-Molecule Organic Blend Memory Transistors.

Controlling the morphology of metal halide perovskite layers during processing is critical for the manufacturing of optoelectronics. Here, a strategy to control the microstructure of solution-processed layered Ruddlesden-Popper-phase perovskite films based on phenethylammonium lead bromide ((PEA)2 PbBr4 ) is reported. The method relies on the addition of the organic semiconductor 2,7-dioctyl[1]benzothieno[3,2-b]benzothiophene (C8 -BTBT) into the perovskite formulation, where it facilitates the formation of large, near-single-crystalline-quality platelet-like (PEA)2 PbBr4 domains overlaid by a ≈5-nm-thin C8 -BTBT layer. Transistors with (PEA)2 PbBr4 /C8 -BTBT channels exhibit an unexpectedly large hysteresis window between forward and return bias sweeps. Material and device analysis combined with theoretical calculations suggest that the C8 -BTBT-rich phase acts as the hole-transporting channel, while the quantum wells in (PEA)2 PbBr4 act as the charge storage element where carriers from the channel are injected, stored, or extracted via tunneling.When tested as a non-volatile memory, the devices exhibit a record memory window (>180V), a high erase/write channel current ratio (104 ), good data retention, and high endurance (>104 cycles). The results here highlight a new memory device concept for application in large-area electronics, while the growth technique can potentially be exploited for the development of other optoelectronic devices including solar cells, photodetectors, and light-emitting diodes.

Thermal analysis of erbium charge storage nanoparticles embedded in organic MIS structure

We report on the self-heating characteristics of fabricated organic MIS structures using rare earth erbium nanoparticle as electrical charge storage elements. The organic MIS structure consists of a semiconductive polymer synthesized by means of doping two non-conductive polymers with an ionic liquid, glycerol. SEM images revealed that the rare earth nanoparticles are charging. A Zeta analyzer was used to determine the size of the nanoparticles with an average diameter size of 92 nm. The capacitance versus voltage hysteresis loops of the MIS structure revealed large window gates with a voltage span of 33 V when a ±20 V sweep scan was performed. FLIR thermograph showed an increase in temperature of 1.3 °C of the MIS structure when connected to an AC power generator at 60 Hz. Doing so increased the time constant of the device by 47% when the device is connected the a power source for 15 min. We also assessed on the relationship of increasing the temperature of the Er nanoparticles increases the amount of charges stored in the MIS capacitor.

A Pentacene -Based Organic Mis Structures

Organic devices based on pentacene thin film are demonstrated. Gold nanoparticles were used as the charge storage elements while pentacene has been used as the active semiconductor layer of Metal-Insulator-Semiconductor (MIS) structures. Polymethylmethacrylate (PMMA) formed the gate insulator. Four devices at different evaporation rates were fabricated and characterised by the atomic force microscopy and electrical characteristics. An optimal deposition rate was identified and supporting topographical images are presented. The device performance strongly correlates with the surface morphology, and the structural properties of the organic thin films have been investigated. The Atomic Force Microscopy (AFM) investigation of very slow evaporated pentacene showed larger grain sizes. Evaporating of gold electrodes on pentacene layers proved to change the morphology of the pentacene surface. The characteristics of bottom contact structures showed much-improved pentacene structures.

4,5-Diazafluorene-Based Donor-Acceptor Small Molecules as Charge Trapping Elements for Tunable Nonvolatile Organic Transistor Memory.

Three diazafluorene derivatives triphenylamine (TPA)(PDAF)n (n = 1, 2, 3) serving as small molecular elements are designed and synthesized via concentrated sulfuric acid mediated Friedel–Crafts reaction. With highly nonplanar topological configuration, TPA(PDAF)3 shows weaker intermolecular interaction in the solid states and thus exhibits single nanomolecular behavior, which is crucial for charge stored and retained in an organic field‐effect transistor (OFET) memory device. Furthermore, diazafluorene derivatives possess a completely separate highest occupied molecular orbital/lowest unoccupied molecular orbital, which offers ideal hole and electron trapping sites. As charge storage elements, triphenylamine groups provide the hole trapping sites, while diazafluorene units provide the electron trapping sites and act as a hole blocking group to restrain the leakage of stored holes trapped in triphenylamine. The pentacene‐based OFET memory device with solution‐processing TPA(PDAF)3 shows a good hole‐trapping ability, high hole trapping density (4.55 × 1012 cm−2), fast trapping speed (<20 ms), a large memory window (89 V), and a tunable ambipolar memory behavior. The optimized device shows a large ON/OFF current ratio (2.85 × 107), good charge retention (>104 s), and reliable endurance properties. This study suggests that diazafluorene based donor–acceptor small molecular elements have great promise for high‐performance OFET memory.

Doped conductive polymers and single-walled carbon nanotubes as charge storage devices

Single-walled carbon nanotubes (SWCNTs), introduced as nano-fillers, were used as charge storage elements. Organic semiconducting polymers were produced by doping organic plasticizers with nonconductive polymers. The nano-fillers were embedded along with organic semiconducting and insulating polymers in constructing metal-insulator-semiconductor (MIS) capacitors classified as organic capacitors. The capacitors were constructed by conventional spin-coating method with metallic electrodes fabricated by means of thermal evaporation. A comparative study was investigated on two device configurations that were built. One with the use of the organic semiconducting polymers and the other with commercially available doped silicon wafer as the semiconductor. Capacitance versus voltage measurements were analyzed on the two configurations to evaluate the storage performance of the devices. The results showed that the device that contained the organic polymeric charge transport layer stored more charge in the SWCNT nano-fillers when compared with the device that contained the silicon wafer. The results also depicted that the embedded SWCNTs were responsible for storing the charge when compared with reference devices that did not contain these nano-fillers.

Charge-Storage Aromatic Amino Compounds for Nonvolatile Organic Transistor Memory Devices.

Here, charge-storage nonvolatile organic field-effect transistor (OFET) memory devices based on interfacial self-assembled molecules are proposed. The functional molecules contain various aromatic amino moieties (N-phenyl-N-pyridyl amino- (PyPN), N-phenyl amino- (PN), and N,N-diphenyl amino- (DPN)) which are linked by a propyl chain to a triethoxysilyl anchor group and act as the interface modifiers and the charge-storage elements. The PyPN-containing pentacene-based memory device (denoted as PyPN device) presents the memory window of 48.43 V, while PN and DPN devices show the memory windows of 24.88 and 8.34 V, respectively. The memory characteristic of the PyPN device can remain stable along with 150 continuous write-read-erase-read cycles. The morphology analysis confirms that three interfacial layers show aggregation due to the N atomic self-catalysis and hydrogen bonding effects. The large aggregate-covered PyPN layer has the full contact area with the pentacene molecules, leading to the high memory performance. In addition, the energy level matching between PyPN molecules and pentacene creates the smallest tunneling barrier and facilitates the injection of the hole carriers from pentacene to the PyPN layer. The experimental memory characteristics are well in agreement with the computational calculation.

Solution-Processed Wide-Bandgap Organic Semiconductor Nanostructures Arrays for Nonvolatile Organic Field-Effect Transistor Memory.

In this paper, the development of organic field-effect transistor (OFET) memory device based on isolated and ordered nanostructures (NSs) arrays of wide-bandgap (WBG) small-molecule organic semiconductor material [2-(9-(4-(octyloxy)phenyl)-9H-fluoren-2-yl)thiophene]3 (WG3 ) is reported. The WG3 NSs are prepared from phase separation by spin-coating blend solutions of WG3 /trimethylolpropane (TMP), and then introduced as charge storage elements for nonvolatile OFET memory devices. Compared to the OFET memory device with smooth WG3 film, the device based on WG3 NSs arrays exhibits significant improvements in memory performance including larger memory window (≈45 V), faster switching speed (≈1 s), stable retention capability (>104 s), and reliable switching properties. A quantitative study of the WG3 NSs morphology reveals that enhanced memory performance is attributed to the improved charge trapping/charge-exciton annihilation efficiency induced by increased contact area between the WG3 NSs and pentacene layer. This versatile solution-processing approach to preparing WG3 NSs arrays as charge trapping sites allows for fabrication of high-performance nonvolatile OFET memory devices, which could be applicable to a wide range of WBG organic semiconductor materials.

A study of selenium nanoparticles as charge storage element for flexible semi-transparent memory devices

Abstract Flexible Semi-Transparent electronic memory would be useful in coming years for integrated flexible transparent electronic devices. However, attaining such flexibility and semi-transparency leads to the boundaries in material composition. Thus, impeding processing speed and device performance. In this work, we present the use of inorganic stable selenium nanoparticles (Se-NPs) as a storage element and hydrogenated amorphous carbon (a-C:H) as an insulating layer in two terminal non-volatile physically flexible and semi-transparent capacitive memory devices (2T-NMDs). Furthermore, a-C:H films can be deposited at very low temperature (

Memory properties of Au nanoparticles prepared by tuning HAuCl4 concentration using low-temperature hydrothermal reaction

An organic memory device with embedded gold nanoparticles (AuNPs) as charge storage elements and polymethylsilsesquioxane (PMSSQ) as organic dielectric layer was fabricated in this work. The AuNPs were prepared using sacrificial hydrothermal reaction on Al template, and the effect of HAuCl4 on size of AuNPs was studied. Field-emission scanning electron microscopy confirmed the increase of particle size with the increase in HAuCl4 concentration. X-ray diffraction analysis confirmed the formation of AuNPs with face-centered cubic (FCC) structure. The electrical properties of the memory system were investigated using a semiconductor characterization system. Current–voltage analysis confirmed the nonvolatile electrical bistability behavior and charge transport mechanism. Capacitance–voltage measurement indicated a memory behavior with flatband voltage shift because the AuNPs trapped and stored charges in the device. The optimal memory properties of AuNPs embedded in PMSSQ were obtained for FCC-structured AuNPs grown in 0.010M HAuCl4, with a mixture of 82±5nm (area density, 1.3×1012m−2) and 42±7nm (area density, 2.7×1012m−2) grain sizes that produced the lowest switch ON voltage of 2.2V and highest flatband voltage of 2.6V.

Integrated Piezoelectric Energy Harvesting and Organic Storage System

Abstract An experimental investigation of an integrated piezo-electric based energy harvester and an organic energy storage device is performed. The energy is harvested from a vibrating composite unimorph beam. The storage device is made out of an organic semiconductor material and storage elements from synthesized nanoparticles. The semiconducting polymer is obtained by blending poly (vinyl alcohol) and poly (acrylic acid) in crystal state polymers with sorbitol acting as the plasticizer. Zinc-Oxide nanoparticles with a diameter size between 50 and 70 nm are used as charge storage elements. A piezoelectric energy generation element made out of macro-fiber composite is used to harvest the energy from the vibrating beam. The harvested energy is stored in the organic capacitor. The performance of the organic device is evaluated through its comparison with commercial capacitors. The results show that the voltage produced was high enough to store the harvested energy in the organic capacitor. The charge and energy levels of the organic capacitor are reported.

High Performance Transparent Transistor Memory Devices Using Nano-Floating Gate of Polymer/ZnO Nanocomposites.

Nano-floating gate memory devices (NFGM) using metal nanoparticles (NPs) covered with an insulating polymer have been considered as a promising electronic device for the next-generation nonvolatile organic memory applications NPs. However, the transparency of the device with metal NPs is restricted to 60~70% due to the light absorption in the visible region caused by the surface plasmon resonance effects of metal NPs. To address this issue, we demonstrate a novel NFGM using the blends of hole-trapping poly (9-(4-vinylphenyl) carbazole) (PVPK) and electron-trapping ZnO NPs as the charge storage element. The memory devices exhibited a remarkably programmable memory window up to 60 V during the program/erase operations, which was attributed to the trapping/detrapping of charge carriers in ZnO NPs/PVPK composite. Furthermore, the devices showed the long-term retention time (>105 s) and WRER test (>200 cycles), indicating excellent electrical reliability and stability. Additionally, the fabricated transistor memory devices exhibited a relatively high transparency of 90% at the wavelength of 500 nm based on the spray-coated PEDOT:PSS as electrode, suggesting high potential for transparent organic electronic memory devices.

Electrical Charging Characteristics of Palladium Nanoparticles Synthesized on Tobacco Mosaic Virus Nanotemplate for Organic Memory Device

In this study, an organic memory using palladium nanoparticles (Pd NPs) synthesized on surface of tobacco mosaic virus (TMV) as charge storage elements was demonstrated on metal-pentacene-insulator-silicon (MPIS) structure. The Pd NPs were preferentially composed on precisely spaced thiol functionalities of genetically modified TMV. Laterally dispersed and assembled Pd NPs TMV layer was acted as a platform enabling electrical charging effect for flatband voltage shift (ΔVFB) of memory capacitor derived from hysteresis of capacitance-voltage (C-V) characteristics. The synthesized Pd NPs TMV was confirmed and imaged by high resolution atomic force microscope (AFM) and electrical charging property of the Pd NPs on the TMV was analyzed by electric force microscopy (EFM) and the C-V measurement. The C-V hysteresis behavior was shown in clockwise direction and memory window of ΔVFB in the (+/−) 3 V and (+/−) 35 V range were 0.15 V and 1.14 V, respectively. This study could provide another nanotemplate example of virus application for organic memory device.

Low operating voltage ambipolar graphene oxide-floating-gate memory devices based on quantum dots

Solution processed quantum dots (QDs) were employed as semiconductor layers in low operating voltage nonvolatile memory devices where graphene oxide (GO) is embedded as a charge storage element.

Dipole Moment Effect of Cyano-Substituted Spirofluorenes on Charge Storage for Organic Transistor Memory

As a fascinating information storage device, organic transistor memory based on molecular charge storage elements (MCSEs) has attracted great research interest. However, the charge storage mechanism of MCSEs is ambiguous due to their complex charge dynamic behaviors. Herein, the dipole moment effects on the charge trapping process and the performance of transistor memory are revealed based on cruciform spiro[fluorene-9,9′-xanthene] (SFXs), incorporating cyano moieties, as the typical electron-withdrawing substitution. The characterization of electrostatic potential (ESP) calculation, UV–vis, photoluminescence, and crystallography of SFXs shows the SFXs MCSEs with weaker dipole moment through symmetrical substitution. A series of prototype transistor memories based on SFXs exhibit an erasable type feature with smart photoresponsive behavior. The weaker dipole moment ones possess larger memory window (∼40 V), higher charge trapping density (>1 × 1013 cm–2), and higher programming speed (1014–1011 cm–2 s–1)....

Electrical Characteristics of Hybrid-Organic Memory Devices Based on Au Nanoparticles

We report on the fabrication and characterization of hybrid-organic memory devices based on gold (Au) nanoparticles that utilize metal–insulator–semiconductor structure. Au nanoparticles were produced by sputtering and inert-gas condensation inside an ultrahigh-vacuum compatible system. The nanoparticles were self-assembled on a silicon dioxide (SiO2)/silicon (Si) substrate, then coated with a poly(methyl methacrylate) (PMMA) insulating layer. Aluminum (Al) electrodes were deposited by thermal evaporation on the Si substrate and the PMMA layer to create a capacitor. The nanoparticles worked as charge storage elements, while the PMMA is the capacitor insulator. The capacitance–voltage (C–V) characteristics of the fabricated devices showed a clockwise hysteresis with a memory window of 3.4 V, indicative of electron injection from the top Al electrode through the PMMA layer into Au nanoparticles. Charge retention was measured at the stress voltage, demonstrating that the devices retain 94% of the charge stored after 3 h of continuous testing.

Novel organic memory devices using Au–Pt–Ag nanoparticles as charge storage elements

The fabrication and characterization of novel organic memory devices based on Au–Pt–Ag nanoparticles, poly(methyl methacrylate) (PMMA), and poly-vinyl-alcohol/poly acrylamide co-acrylic acid with glycerol ionic liquid (PVA–PAA–glycerol) are reported in this work. The devices are fabricated based on metal–insulator–semiconductor (MIS) structure. PMMA is utilized as an organic insulator, while PVA–PAA–glycerol film functions as a semiconducting polymer where its conductivity is controlled by controlling glycerol concentration. Thermally evaporated aluminum electrodes are used as bottom and top electrodes for the fabricated devices. The fabrication process is simple and has high device production yield. Capacitance–voltage (C(V)) measurements of the fabricated devices demonstrate hysteresis widows indicating charge storage within the nanoparticles. The fabricated devices have potential to be used for applications since they retain charge for reasonable time.

Fabrication of solution processed carbon nanotube embedded polyvinyl alcohol composite film for non-volatile memory device.

Carbon nanotubes (CNTs) were synthesized by chemical vapor deposition using nickel coated stainless steel prepared by electrophoretic deposition. CNTs were embedded in polyvinyl alcohol (PVA) which acts as an organic insulator to fabricate Si/PVA/CNT/PVA/Al Metal-Insulator-Semiconductor type memory devices. The effect of CNT content in the charge storage capacity of PVA-CNT composite film was investigated. The hysteresis obtained from the capacitance-voltage (CV) measurement resulted in a memory window of 1.9 V with 3% CNT loading with the gate voltage sweep of +/- 6 V at 1 MHz under room temperature. The memory window of the devices was due to electron injection into the CNT charge storage elements from the top electrode through PVA. The extensive pi-conjugation along the CNT axis traps the electrons in the CNT network. The ON/OFF state current ratio of Si/Al/PVA-CNT/AI device with 3% CNT in PVA demonstrated significantly a lower turn-on voltage of -1 V and a higher ON/OFF state current ratio of 10(7). The non-volatile and reprogrammable switching behavior of the device demonstrated the characteristic of a rewritable memory.