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The impedance spectroscopy analysis is utilized to probe the modifications of charge carrier dynamics arising from interface mixing in a solution-processed organic light emitting diode.

Oxide thin-film transistors (TFTs) have attracted much attention because they can be applied to flexible and large-scaled switching devices. Especially, oxide semiconductors (OSs) have been developed as active layers of TFTs. Among them, indium-gallium-zinc oxide (IGZO) is actively used in the organic light-emitting diode display field. However, despite their superior off-state properties, IGZO TFTs are limited by low field-effect mobility, which critically affects display resolution and power consumption. Herein, we determine new working mechanisms in dual-stacked OS, and based on this, we develop a dual-stacked OS-based TFT with improved performance: high field-effect mobility (∼80 cm2/V·s), ideal threshold voltage near 0 V, high on-off current ratio (>109), and good stability at bias stress. Induced areas are formed at the interface by the band offset: band offset-induced area (BOIA) and BOIA-induced area (BIA). They connect the gate bias-induced area (GBIA) and electrode bias-induced area (EBIA), resulting in high current flow. Equivalent circuit modeling and the transmission line method are also introduced for more precise verification. By verifying current change with gate voltage in the single OS layer, the current flowing direction in the dual-stacked OS is calculated and estimated. This is powerful evidence to understand the conduction mechanism in a dual-stacked OS-based TFT, and it will provide new design rules for high-performance OS-based TFTs.

Halide perovskites have drawn considerable attention as a remarkable material in advanced optoelectronics. However, toxicity and poor stability of halide perovskites are major challenges hindering ...

The research on amorphous indium–gallium–zinc oxide (IGZO) Schottky contacts has received much attention for various electronic applications due to their high uniformity, excellent electrical prope...

Li+ electrolyte-gated transistors (EGTs) have attracted significant attention as artificial synapses because of the fast response of Li+ ion, low operating voltage, and applicability to flexible electronics. Due to the inherent nature of Li+ ion, Li+ EGTs show, however, limitations, such as poor long-term synaptic plasticity and nonlinear/nonsymmetric conductance update, which hinder the practical applications of artificial synapses. Herein, Li+ EGTs integrated with poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) ferroelectric polymer as a channel–electrolyte interlayer are presented. Owing to the polarized domains of PVDF-TrFE, the transport of Li+ ions at the channel–electrolyte interface is accelerated, and Li+ ions effectively penetrate the channel. Moreover, the self-diffusion of Li+ ions from the channel to the electrolyte is suppressed by the downward polarized domains. Li+ EGTs, therefore, successfully demonstrate synaptic characteristics, including excitatory postsynaptic current, short-/long-term synaptic plasticity, and paired-pulse facilitation. Also, conductance update in Li+ EGTs shows a dynamic range ( Gmax/ Gmin) of 92.42, high linearity, and distinct stability over 100 cycles. Based on their synaptic characteristics, inference simulations using a convolution neural network for the CIFAR-10 dataset imply that Li+ EGTs are suitable as artificial synapses with an inference accuracy of 89.13%. The new methodological approach addressing modulation of ion dynamics at the interface is introduced for developing practical synaptic devices.

Recently, metal-insulator-oxide semiconductor-metal (MIOSM) thin-film diodes (TFDs) have received attention as next-generation diodes due to their high rectification ratio and broad option on the operating voltage range. Nevertheless, precise turn-on voltage control of the MIOSM TFDs has been required for circuit design convenience. Here, we present a simple and accurate method of controlling the turn-on voltage of MIOSM TFDs. Studies on current-voltage characteristics reveal that controlling carrier injection into trap states in an insulator by oxygen vacancy variation of the oxide semiconductor plays a key role in the turn-on voltage shift of MIOSM TFDs. Moreover, by controlling the trap states in the insulator, the finely tuned turn-on voltages of the MIOSM TFDs are demonstrated for both low-voltage- and high-voltage-driving diodes. MIOSM TFDs with adjustable turn-on voltage, which can be built more efficiently and accurately, are expected to make oxide-based circuit designs more precise and straightforward.

The Li metal anode has high theoretical specific capacity and low redox potential, making it suitable as an anode material for next-generation Li ion-based batteries (LIBs); however, challenges remain due to its unstable solid electrolyte interphase (SEI). In this study, we applied graphene-coated aramid attached to an uncoated aramid separator fabricated using a simple painting method to a Li metal anode to address the issues caused by the unstable SEI via fluorinated metathesis on a conjugated carbon network (CCN). The graphene-coated surface was partially fluorinated in a specific solvent environment, and as the Li+ ions were plated, the fluorinated surface induced formation of LiF as a chemically stable SEI component. Additionally, we demonstrated the successful application of fluorinated metathesis using other CCN materials, such as carbon black and activated carbon. The experimental results indicated that the CCN materials induced LiF via fluorination, and that the negative functionalities and lattice structure of the CCN materials affected the fluorination. These results demonstrated the effectiveness of this novel method for stabilizing a Li metal surface using a graphite pencil.

An oxide thin-film diode (TFD) is required as a fundamental building block of the next-generation electronic circuit along with an oxide thin-film transistor (TFT). However, compared to recent deve...

In this article, the atmospheric pressure plasma (APP) treatment method is proposed to solve the instability problem under a long-term electrical bias stress through the semiconductor surface treatment without degrading the excellent electrical characteristics of oxide thin-film transistors (TFTs). The high-energy oxygen radicals produced by the APP without a vacuum system affect the electrical properties by quickly and easily changing the chemical state of the oxygen-related bonds in the semiconductor. Consequently, the amorphous indium gallium zinc oxide TFTs with suitable APP treatment showed excellent bias stress stability and electrical characteristics in comparison with the APP-untreated oxide TFTs. The threshold voltage shift after the negative gate bias stress and positive gate bias stress duration of 1 h significantly reduced from −9.9 to −0.7 V and from +6.7 to +0.5 V, respectively. In addition, the average field-effect mobility remarkably enhanced from 10.8 to 14.8 cm2/Vs and the hysteresis behavior reduced from 0.31 to 0.12 V while maintaining the key parameters of TFTs such as subthreshold swing, ON/OFF ratio, and ${V}_{ \mathrm{\scriptscriptstyle ON}}$ .

Recently, organic compounds are considered as promising candidates for application in next-generation energy storage systems to overcome the disadvantages of conventional inorganic cathode materials, including their low specific capacity and poor disposal systems. In particular, pillar[5]quinone (P5Q) is very effective as it provides active sites that favor Li uptake and promote a high theoretical capacity. Herein, we propose P5Q-derived cathodes, which are enveloped in multi-walled carbon nanotubes and cellulose nanofibers (CNFs), fabricated by a simple vacuum-filtering method. The designed cathode solves the issues associated with organic materials, including their high solubilities in aprotic electrolytes and low conductivities. Furthermore, CNFs are introduced as alternatives to conventional polyolefin separators. CNF separators can effectively suppress the dissolution of active materials in liquid electrolytes. In addition, CNFs improve ionic conductivity (0.88 mS cm−1), electrolyte wettability (electrolyte uptake: 333.41%, porosity: 70 ± 5%), and thermal shrinkage in contrast to conventional polyolefin separators. The Li-ion battery, assembled with the suggested P5Q cathode and CNF separator, exhibits highly stable capacity retention (76.5% after 50 cycles at a 0.2 C rate) and good rate capability, although an organic electrolyte is used.

Recently, lithium–sulfur batteries (LSBs) have been highlighted as next-generation batteries due to the high theoretical capacity of the sulfur nonmetal and Li metal. However, LSBs are difficult to be commercialized because of the continuous capacity fading phenomenon derived from the shuttle effect of lithium polysulfide. Herein, a novel organic–inorganic composite separator composed of poly(vinylidene fluoride-co-hexafluoropropylene) and anodic aluminum oxide is proposed to overcome these limitations. The proposed separator strongly reduces the dissolution issue of lithium polysulfide and considerably limits the movement of polysulfide. Moreover, it improves the stability of the lithium metal anode by evenly distributing the flux of lithium ions. Also, it shows excellent thermal stability and good electrolyte wettability. Therefore, the ionic conductivity shows a high value of more than 1 mS cm−1, and the coulombic efficiency is over 99%. The LSBs assembled with the composite separator exhibit the maintained specific capacity over of 75% after 100 cycles at 0.5C.

We verified the origin of water-infiltration-induced electricity generation by an ionovoltaic effect, specifically, ion–surface interaction induced potential asymmetry in porous structures. When 20 μl of water (NaCl, 0.1 M) infiltrates into a porous CuO nanowire film, electrical power of ∼0.45 V and ∼0.23 μA is produced for 40 minutes. Moreover, a method of proportionally amplifying electricity is presented, and the practicability is shown by turning on an LED with infiltration of eight seawater droplets.

Owing to its high theoretical capacity (3860 mA h g−1), Li metal is emerging as a next-generation anode material. However, its volume expansion is a major obstacle in its commercialization because it causes the collapse of the solid electrolyte interphase layer and lowers the coulombic efficiency of the battery. Moreover, it induces dendrite formation, which causes internal short circuits. To overcome this obstacle, we propose the use of a cross-linked poly(ethylene glycol) dimethacrylate (c-PEGDMA) film containing ethylene oxide units as a protective layer for the metal surface. We prepared the c-PEGDMA by using a simple solventless process. It was coated on the surface of Li metal for a short time and thermally cured. The film was found to inhibit the volume expansion of Li metal during cycling, thereby reducing coulombic efficiency degradation and dendrite growth. The proposed surface stabilization technique is expected to be effective for Li metal batteries.

Lithium metal is considered the most promising anode material because of its highest theoretical capacity and lowest electrode potential among the candidate materials. However, Li metal batteries have not been commercialized yet owing to their poor cycle stability. To solve this problem, many studies have reported that the addition of chemically stable LiF to the artificial solid electrolyte interphase (SEI) layer can effectively inhibit the low irreversibility of and dendrite growth on Li metal. However, this measure is inadequate for achieving the desired performance, and it introduces difficulties in the fabrication process. This study employs an in situ LiF protective layer (PL) to stabilize the surface of Li metal. This artificial SEI layer that includes LiF can be fabricated simply through thermal curing of an F-rich material on the surface of Li metal. This “in situ LiF PL” effectively prevents volume expansion of Li metal, resulting in a capacity retention of 52.1% after 1000 cycles at 5.0C. The proposed artificial SEI layer design offers an alternative strategy for stabilizing the surface of Li metal.

An ionovoltaic device with an electrolyte–insulator–semiconductor structure is drawing much attention due to the electrical energy which can be generated by the movement of a water droplet. Herein,...

Li metal is an ideal anode material for batteries based on Li ion because of its high theoretical specific capacity and low redox potential. However, the repeated formation and collapse of solid el...

Evaporation-induced electricity generation, harnessing natural vaporization of water, is spotlighted as a promising energy conversion system with showing off remarkable characteristics such as cont...

Transferring charge carriers through an insulator film between two metal electrodes is a major issue in various electronic devices, including metal/insulator/metal (MIM) diodes and resistive switch...

In a MIS (Metal/Insulator/Semiconductor) structure consisting of two terminals, a systematic analysis of the electrical charge transport mechanism through an insulator is essential for advanced electronic application devices such as next-generation memories based on resistance differences. Herein, we have verified the charge transfer phenomenon in MIOS (Metal/Insulator/Oxide Semiconductor) diodes through a defect engineering of the insulator. By selectively generating the oxygen vacancies in the insulator (Al2O3), the MIOS diode rectification of the P++-Si anode/Al2O3/IGZO cathode reached 107 at 1.8 V and considerably suppressed the leakage current. Studying the current-voltage characteristics of MIOS diodes shows that the charge carrier transport mechanism can vary depending on the defect density as well as the difference between the CBM (conduction band minimum) of the semiconductor and the oxygen vacancy energy level of the insulator.

An ionovoltaic device that generates electric energy by the ad/desorption of ions on a solid–liquid interface, as water droplets move on a solid surface, has a unique operation mechanism. Here, we ...

Various efforts have been made to fabricate oxide thin-film diodes (TFDs) that will be applied to next-generation electronics to ensure thin, lightweight, and reliable operation. However, p–n-junct...

Urea detection has been studied extensively because urea is an important indicator in medical, environmental and industrial fields. Despite the considerable body of research in this area, limitations such as the need for an external power source and the complex operation of electrochemical flow cells remain. Herein, we introduce a novel urea sensing method that accomplishes urea detection with a single droplet of an analyte using a pH-sensitive ionovoltaic transducer and an enzyme attached glass probe. An ionovoltaic transducer converts ion dynamic phenomena at the solid-liquid interface directly into electrical signals without an external power source or additional electrochemical flow cells. With a single droplet of an analyte containing urea (140 μL), the output voltage is inverted within two minutes by surface potential changes induced by the urea decomposition depending on urea concentration in the range of 1–50 mM. Furthermore, in a selective experiment with various biomolecules such as glucose, ascorbic acid, and lactic acid, the inversion of the output voltage occurred selectively only in the urea containing analyte, which confirmed the feasibility of the proposed unique biosensor. We believe that the combination of the ionovoltaic transducer and the enzyme attached probe will greatly broaden the scope of applications of this novel biosensor.

The stability and control of copper (Cu) electrode application in oxide semiconductor indium gallium zinc oxide (IGZO) can improve the resistance–capacitance (RC) delay, which is greatly critical f...

Until now, development of conventional electronic devices has mainly focused on performance, and e-waste disposal has been neglected. To alleviate e-waste disposal problems, the use of naturally degradable materials as electronic components has been studied. While most research on such materials has focused on the substrate, other components such as dielectric insulators have not been widely studied. Here, we developed a poly-methacrylated tannic acid (PMTA) naturally degradable dielectric material with good electrical breakdown strength (5.4 MV cm−1), good long-term stability in ambient, and a stable surface. Pentacene thin-film transistors (TFTs) with a PMTA dielectric insulator layer showed reasonable field effect mobility of 0.2 cm2 V−1 s−1 at −20 V of gate voltage (Vg). In addition, the pentacene TFTs with a PMTA dielectric insulator layer and a polyvinyl alcohol substrate show a good degradability in natural; the TFTs were fully decomposed within 8 days in phosphate buffered saline (PBS buffer solution). Also, the TFTs with a PMTA dielectric insulator layer were fully decomposed within 19 days in 3.5 wt% sodium chloride solution, similar to seawater, which has a good potential for reduction of e-waste.

In current nanoscale semiconductor fabrications, high dielectric materials and ultrathin multilayers have been selected to improve the performance of the devices. Thus, interface effects between films and the quantification of surface information are becoming key issues for determining the performance of the semiconductor devices. In this paper, we developed an easy, accurate, and nondestructive diagnosis to investigate the interface effect of hafnium oxide ultrathin films. A roughness scaling method that artificially modified silicon surfaces with a maximum peak-to-valley roughness range of a few nanometers was introduced to examine the effect on the underlayer roughness. The critical overlayer roughness was be defined by the transition of RMS roughness which was 0.18 nm for the 3 nm thick hafnium oxide film. Subsequently, for the inline diagnostic application of semiconductor fabrication, the roughness of a mass produced hafnium film was investigated. Finally, we confirmed that the result was below the threshold set by our critical roughness. The RMS roughness of the mass produced hafnium oxide film was 0.11 nm at a 500 nm field of view. Therefore, we expect that the quantified and standardized critical roughness managements will contribute to improvement of the production yield.

An all-inorganic heterojunction phototransistor using a highly stable perovskite (CsPbIxBr3−x) and amorphous In–Ga–Zn–O (IGZO) double-layer is introduced to enhance the sensing performance of optoelectronic devices and to expand their detecting range from the ultraviolet to the visible light region. Despite the high-performance photoelectric properties of CsPbI3 perovskites retaining the α-phase, actual applications of the perovskite film are considerably hindered by the phase instability under ambient conditions. Here, in order to improve the long-term stability of the α-phase perovskite, we propose a multiple anion strategy in the perovskite structure. The developed CsPbIxBr3−x film is applied with bi-anion IxBr3−x instead of I3 by adding CsBr and PbBr2 in the CsPbI3 precursor solution. Using the optimized CsPbIxBr3−x film with 12 wt% of the additives CsBr and PbBr2 in the CsPbI3 precursor solution, we demonstrate an all-inorganic visible light detector based on a heterojunction phototransistor with a p++-Si/SiO2/IGZO/CsPbIxBr3−x/Ti–Al–Ti structure, in which IGZO and CsPbIxBr3−x are used as a charge transport layer and a light absorption layer, respectively. The phototransistor exhibits a responsivity of 26.48 A W−1, a detectivity of 8.42 × 1014 Jones, and an external quantum efficiency of 51% under visible light illumination (635 nm). In particular, it shows excellent stability over 1 month under ambient conditions.

Synaptic devices that mimic biological neurons have attracted much attention for brain-inspired neuromorphic computing. Especially, synaptic thin-film transistors (TFTs) have emerged with simultaneous signal processing and information storage advantages. However, the analysis of excitatory postsynaptic current (EPSC) relies on an empirical model such as a serial RC circuit, which limits a systematic and in-depth study of synaptic devices in terms of material and electrical properties. Herein, the single-pulse-driven synaptic EPSC (SPSE) model, including capacitive effect and information of the synaptic window, is analytically proposed. The SPSE model can simulate EPSC of synaptic devices at given TFT-operating conditions. EPSC with the SPSE model can be characterized with quantified parameters for the capacitive effects and the synaptic windows, which also depend on the electrical condition applied to TFTs. Various kinds of synaptic-TFTs with different gate insulators (e.g., SiO2 and ion-gel) are used to confirm the performance of the SPSE model. For example, the SPSE model can capture the long-term robustness of ion-gel-based TFTs with specific quantified parameters. In addition, the SPSE model enables the estimation of energy consumption, which can potentially be leveraged to compare the energy cost of EPSC fairly. The SPSE model can provide a guideline to understand the physical properties of synaptic TFTs.

Recently, aqueous method has attracted lots of attention because it enables the solution-processed metal oxide thin film with high electrical properties in low temperature fabrication condition to various flexible devices. Focusing the development of aqueous route, many researchers are only focused on metal oxide materials. However, for expansive application of the aqueous-based metal oxide films, the systematic study of performance change with process variables for the development of aqueous-based metal oxide insulator film is urgently required. Here, we propose importance of process variables to achieve high electrical-performance metal oxide insulator based on the aqueous method. We found that the significant process variables including precursor solution temperature and humidity during the spin-coating process strongly affect chemical, physical, and electrical properties of AlOx insulators. Through the optimization of significant variables in process, an AlOx insulator with a leakage current value approximately 105 times smaller and a breakdown voltage value approximately 2–3 times greater than un-optimized AlOx was realized. Finally, by introducing the optimized AlOx insulators to solution-processed InOx TFTs, we successfully achieved InOx/AlOx TFTs with remarkably high average field-effect mobility of ∼52 cm2 V−1 s−1 and on/off current ratio of 106 at fabrication temperature of 250 °C.

Metal oxide semiconductors doped with additional inorganic cations have insufficient electron mobility for next-generation electronic devices so strategies to realize the semiconductors exhibiting stability and high performance are required. To overcome the limitations of conventional inorganic cation doping to improve the electrical characteristics and stability of metal oxide semiconductors, we propose solution-processed high-performance metal oxide thin-film transistors (TFTs) by incorporating polyaniline (PANI), a conductive polymer, in a metal oxide matrix. The chemical interaction between the metal oxide and PANI demonstrated that the defect sites and crystallinity of the semiconductor layer are controllable. In addition, the change in oxygen-related chemical bonding of PANI-doped indium oxide (InOx) TFTs induces superior electrical characteristics compared to pristine InOx TFTs, even though trace amounts of PANI are doped in the semiconductor. In particular, the average field-effect mobility remarkably enhanced from 15.02 to 26.58 cm2 V-1 s-1, the on/off current ratio improved from 108 to 109, and the threshold voltage became close to 0 V actually from -7.9 to -1.4 V.

The change in electrical properties of electrodes by adsorption or desorption at interfaces is a well-known phenomenon required for signal production in electrically transduced sensing technologies. Furthermore, in terms of electrolyte-insulator-semiconductor (EIS) structure, several studies of energy conversion techniques focused on ion-adsorption at the solid-liquid interface have suggested that the electric signal is generated by ionovoltaic phenomena. However, finding substantial clues for the ion-adsorption phenomena in the EIS structure is still a difficult task because direct evidence for carrier accumulation in semiconductors by Coulomb interactions is insufficient. Here, a sophisticated Hall measurement system is demonstrated to quantitatively analyze accumulated electron density-change inside the semiconductor depending on the ion-adsorption at the solid-liquid interface. Also, an enhanced EIS-structured device is designed in an aqueous-soaked system that works with the ionovoltaic principle to monitor the ion-dynamics in liquid electrolyte media, interestingly confirming ion-concentration dependence and ion-specificity by generated peak voltages. This newly introduced peculiar method contributes to an in-depth understanding of the ionovoltaic phenomena in terms of carrier actions in the semiconductors and ionic behaviors in the aqueous-bulk phases, providing informative analysis about interfacial adsorptions that can expand the scope of ion-sensing platforms.