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The praseodymium-doped indium zinc oxide (PrIZO) thin-film transistor (TFT) is promising for applications in flat-panel displays, due to its high carrier mobility and stability. Nevertheless, there are few studies on the mechanism of annealing on PrIZO films and the fabrication of flexible devices. In this work, we first optimized the annealing-process parameters on the glass substrate. As the annealing temperature rises, the film tends to be denser and obtains a lower surface roughness, a narrower optical-band gap and less oxygen-vacancy content. However, the μ-PCD test shows the 250 °C-annealed film obtains the least defects. And the PrIZO TFT annealed at 250 °C exhibited a desired performance with a saturation mobility (μsat) of 14.26 cm2·V−1·s−1, a subthreshold swing (SS) of 0.14 V·dec−1, an interface trap density (Dit) of 3.17 × 1011, an Ion/Ioff ratio of 1.83 × 108 and a threshold voltage (Vth) of −1.15 V. The flexible devices were prepared using the optimized parameters on the Polyimide (PI) substrate and subjected to static bending tests. After bending at a radius of 5 mm, the mobility of devices decreases slightly from 12.48 to 10.87 cm2·V−1·s−1, demonstrating the great potential of PrIZO for flexible displays.

As the competition intensifies in enhancing the integration and performance of integrated circuits, in accordance with the famous Moore’s Law, higher performance and smaller size requirements are imposed on the dielectric layers in electronic devices. Compared to vacuum methods, the production cost of preparing dielectric layers via solution methods is lower, and the preparation cycle is shorter. This paper utilizes a low-temperature self-exothermic reaction based on the solution method to prepare high-performance Al2O3 dielectric thin films that are compatible with flexible substrates. In this paper, we first established two non-self-exothermic systems: one with pure aluminum nitrate and one with pure aluminum acetylacetonate. Additionally, we set up one self-exothermic system where aluminum nitrate and aluminum acetylacetonate were mixed in a 1:1 ratio. Tests revealed that the leakage current density and dielectric constant of the self-exothermic system devices were significantly optimized compared to the two non-self-exothermic system devices, indicating that the self-exothermic reaction can effectively improve the quality of the dielectric film. This paper further established two self-exothermic systems with aluminum nitrate and aluminum acetylacetonate mixed in 2:1 and 1:2 ratios, respectively, for comparison. The results indicate that as the proportion of aluminum nitrate increases, the overall dielectric performance of the devices improves. The best overall performance occurs when aluminum nitrate and aluminum acetylacetonate are mixed in a ratio of 2:1: The film surface is smooth without cracks; the surface roughness is 0.747 ± 0.045 nm; the visible light transmittance reaches up to 98%; on the basis of this film, MIM devices were fabricated, with tested leakage current density as low as 1.08 × 10−8 A/cm2 @1 MV and a relative dielectric constant as high as 8.61 ± 0.06, demonstrating excellent electrical performance.

This article aims to explore the most optimal pulsed laser energy density when using the pulsed laser deposition (PLD) process to prepare the MoS2 films. We gradually increased the pulsed laser energy density from 70 mJ·cm−2 to 110 mJ·cm−2 and finally determined that 100 mJ·cm−2 was the best-pulsed laser energy density for MoS2 films by PLD. The surface morphology and crystallization of the MoS2 films prepared under this condition are the best. The films consist of a high-crystallized 2H-MoS2 phase with strong (002) preferential orientation, and their direct optical band gap (Eg) is 1.614 eV. At the same time, the Si/MoS2 heterojunction prepared under the optimal pulsed laser energy density shows an opening voltage of 0.61 V and a rectification ratio of 457.0.

We propose an amorphous metal oxide thin film transistor photo-capacitance model in the depletion region that takes Fermi level splitting and band-bending rearrangement into consideration. The split Fermi level is used to characterize the variation in trapped electrons under illumination. Those trapped electrons are excited by optical energy transport under the electric field induced by gate voltage, changing the charge density in the space charge and inducing the rearrangement of band bending. By comparing the data calculated from the model with the test data under three different illumination conditions, that is, 808, 635, and 520 nm, we verify the correctness of this model. Furthermore, the fitting results were in accordance with the general law: the higher the photon energy, the higher the energy level splitting.

The method of improving the electrochromic properties of tungsten oxide by doping has attracted great interest. In this study, we successfully fabricated nanostructured tungsten oxide with different copper doping concentrations by a solvothermal method using copper chloride dihydrate and tungsten hexachloride as precursors. We found that the area-specific capacitance of the films gradually increased with the increase in doping concentration. The products were characterized by x-ray photoelectron spectroscopy, x-ray diffraction, scanning electron microscopy, cyclic voltammetry, and chronoamperometry. The results show that the films we fabricated are reticular structures composed of nanowires. The doping of copper can improve the electron conductivity and shorten the ion transmission distance, thus improving energy storage properties. When the doping concentration is 7% and the annealing temperature is 200 °C, the film had the largest surface capacitance of 17.89 mF/cm2 and the capacitance retention reached 58.23%.

In this study, a KrF excimer laser with a high-absorption coefficient in metal oxide films and a wavelength of 248 nm was selected for the post-processing of a film and metal oxide thin film transistor (MOTFT). Due to the poor negative bias illumination stress (NBIS) stability of indium gallium zinc oxide thin film transistor (IGZO-TFT) devices, terbium-doped Tb:In2O3 material was selected as the target of this study. The XPS test revealed the presence of both Tb3+ and Tb4+ ions in the Tb:In2O3 film. It was hypothesized that the peak of the laser thermal effect was reduced and the action time was prolonged by the f-f jump of Tb3+ ions and the C-T jump of Tb4+ ions during the laser treatment. Studies related to the treatment of Tb:In2O3 films with different laser energy densities have been carried out. It is shown that as the laser energy density increases, the film density increases, the thickness decreases, the carrier concentration increases, and the optical band gap widens. Terbium has a low electronegativity (1.1 eV) and a high Tb-O dissociation energy (707 kJ/mol), which brings about a large lattice distortion. The Tb:In2O3 films did not show significant crystallization even under laser energy density treatment of up to 250 mJ/cm2. Compared with pure In2O3-TFT, the doping of Tb ions effectively reduces the off-state current (1.16 × 10−11 A vs. 1.66 × 10−12 A), improves the switching current ratio (1.63 × 106 vs. 1.34 × 107) and improves the NBIS stability (ΔVON = −10.4 V vs. 6.4 V) and positive bias illumination stress (PBIS) stability (ΔVON = 8 V vs. 1.6 V).

Thin-film transistors based on amorphous oxide semiconductors have promising applications, but their stability is hampered by negative bias illumination stress. Here, a systematic study of lanthanide-doped indium oxide semiconductors reveals that Pr and Tb are most efficient in improving the photostability of devices.

The work presents a novel pixel circuit which breaks the constraint that the PWM driving method combined with internal compensating is unable to achieve a high-bit display. By adding another TFT to transform the equal division of PWM to unequally divided subfields, the bit of a 240 Hz 10-row panel is improved from 3 bits to 8 bits, which is a great breakthrough for bits improving in the fields of PWM driving and internal compensating. Furthermore, simulation results of the original 6T1C circuit and revised 7T1C circuit demonstrate that the current error ratio is almost the same, indicating that this revising 7T1C circuit is suitable for bits improving without sacrificing the circuit margin.

Abstract In this work, a low leakage current ZrO2 was fabricated for sputter indium gallium zinc oxide (IGZO) thin-film transistor using direct inkjet-printing technology. Spin-coated and direct inkjet-printed ZrO2 were prepared to investigate the film formation process and electrical performance for different process. Homogeneous ZrO2 films were observed through the high-resolution TEM images. The chemical structure of ZrO2 films were investigated by XPS measurements. The inkjet-printed ZrO2 layer upon IGZO showed a superior performance on mobility and off state current, but a large V th shift under positive bias stress. As a result, the TFT device based on inkjet-printed ZrO2 exhibited a saturation mobility of 12.4 cm2/Vs, an Ion/Ioff ratio of 106, a turn on voltage of 0 V and a 1.4-V V th shift after 1-h PBS strain. Higher density films with less oxygen vacancy were responsible for low off state current for the printed ZrO2 device. The mechanism of deteriorated performance on PBS test can be ascribed to the In-rich region formed at the back channel which easily absorbs H2O and oxygen. The absorbed H2O and oxygen capture electrons under positive bias stress, serving as acceptors in TFT device. This work demonstrates the film formation process of direct inkjet-printed and spin-coated oxide films and reveals the potential of direct inkjet-printed oxide dielectric in high-performance oxide TFT device.

The applications of thin-film transistors (TFTs) based on oxide semiconductors are limited due to instability under negative bias illumination stress (NBIS). Here, we report TFTs based on solution-processed In2O3 semiconductors doped with Pr4+ or Tb4+, which can effectively improve the NBIS stability. The differences between the Pr4+-doped In2O3 (Pr:In2O3) and Tb4+-doped In2O3 (Tb:In2O3) are investigated in detail. The undoped In2O3 TFTs with different annealing temperatures exhibit poor NBIS stability with serious turn-on voltage shift (ΔVon). After doping with Pr4+/Tb4+, the TFTs show greatly improved NBIS stability. As the annealing temperature increases, the Pr:In2O3 TFTs have poorer NBIS stability (ΔVon are −3.2, −4.8, and −4.8 V for annealing temperature of 300, 350, and 400 °C, respectively), while the Tb:In2O3 TFTs have better NBIS stability (ΔVon are −3.6, −3.6, and −1.2 V for annealing temperature of 300, 350, and 400 ℃, respectively). Further studies reveal that the improvement of the NBIS stability of the Pr4+/Tb4+:In2O3 TFTs is attributed to the absorption of the illuminated light by the Pr/Tb4fn—O2p6 to Pr/Tb 4fn+1—O2p5 charge transfer (CT) transition and downconversion of the light to nonradiative transition with a relatively short relaxation time compared to the ionization process of the oxygen vacancies. The higher NBIS stability of Tb:In2O3 TFTs compared to Pr:In2O3 TFTs is ascribed to the smaller ion radius of Tb4+ and the lower energy level of Tb 4f7 with a isotropic half-full configuration compared to that of Pr 4f1, which would make it easier for the Tb4+ to absorb the visible light than the Pr4+.

Electrochromic materials have been considered as a new way to achieve energy savings in the building sector due to their potential applications in smart windows, cars, aircrafts, etc. However, the high cost of manufacturing ECDs using the conventional manufacturing methods has limited its commercialization. It is the advantages of low cost as well as resource saving, green environment protection, flexibility and large area production that make printing electronic technology fit for manufacturing electrochromic devices. This paper reviews the progress of research on printed electrochromic devices (ECDs), detailing the preparation of ECDs by screen printing, inkjet printing and 3D printing, using the scientific properties of discrete definition printing method. Up to now, screen printing holds the largest share in the electrochromic industry due to its low cost and large ink output nature, which makes it suitable especially for printing on large surfaces. Though inkjet printing has the advantages of high precision and the highest coloration efficiency (CE) can be up to 542 ± 10 cm2C–1, it has developed smoothly, and has not shown rigid needs. Inkjet printing is suitable for the personalized printing production of high precision and small batch electronic devices. Since 3D printing is a new manufacturing technology in the 21st century, with the characteristics of integrated molding and being highly controllable, which make it suitable for customized printing of complex devices, such as all kinds of sensors, it has gained increasing attention in the past decade. Finally, the possibility of combining screen printing with inkjet printing to produce high performance ECDs is discussed.

Flexible electronic devices have received great attention in the fields of foldable electronic devices, wearable electronic devices, displays, actuators, synaptic bionics and so on. Among them, high-performance flexible memory for information storage and processing is an important part. Due to its simple structure and non-volatile characteristics, flexible resistive random access memory (RRAM) is the most likely flexible memory to achieve full commercialization. At present, the minimum bending radius of flexible RRAM can reach 2 mm and the maximum ON/OFF ratio (storage window) can reach 108. However, there are some defects in reliability and durability. In the bending process, the cracks are the main cause of device failure. The charge trap sites provided by appropriate doping or the use of amorphous nanostructures can make the conductive filaments of flexible RRAM steadier. Flexible electrodes with high conductivity and flexible dielectric with stable storage properties are the main development directions of flexible RRAM materials in the future.

Recently, tin oxide (SnO2) has been the preferred thin film material for semiconductor devices such as thin-film transistors (TFTs) due to its low cost, non-toxicity, and superior electrical performance. However, the high oxygen vacancy (VO) concentration leads to poor performance of SnO2 thin films and devices. In this paper, with tetraethyl orthosilicate (TEOS) as the Si source, which can decompose to release heat and supply energy when annealing, Si doped SnO2 (STO) films and inverted staggered STO TFTs were successfully fabricated by a solution method. An XPS analysis showed that Si doping can effectively inhibit the formation of VO, thus reducing the carrier concentration and improving the quality of SnO2 films. In addition, the heat released from TEOS can modestly lower the preparation temperature of STO films. By optimizing the annealing temperature and Si doping content, 350 °C annealed STO TFTs with 5 at.% Si exhibited the best device performance: Ioff was as low as 10−10 A, Ion/Ioff reached a magnitude of 104, and Von was 1.51 V. Utilizing TEOS as an Si source has a certain reference significance for solution-processed metal oxide thin films in the future.

For making full use of the discoloration function of electrochromic (EC) devices and better show the charge and discharge states of supercapacitors (SCs), electrochromic supercapacitors (ECSCs) have attracted much attention and expectations in recent years. The research progress of tungsten-oxide-based electrochromic supercapacitors (ECSCs) in recent years is reviewed in this paper. Nanostructured tungsten oxide is widely used to facilitate ion implantation/extraction and increase the porosity of the electrode. The low-dimensional nanostructured tungsten oxide was compared in four respects: material scale, electrode life, coloring efficiency, and specific capacitance. Due to the mechanics and ductility of nano-tungsten oxide electrodes, they are very suitable for the preparation of flexible ECSCs. With the application of an organic protective layer and metal nanowire conductive electrode, the device has higher coloring efficiency and a lower activation voltage. Finally, this paper indicates that in the future, WO3-based ECSCs will develop in the direction of self-supporting power supply to meet the needs of use.

Capacitors play an increasingly important role in hybrid integrated circuits, while the MIM capacitors with high capacitance density and small thickness can meet the needs of high integration. Generally speaking, the films prepared with a single metal oxide dielectric often achieve a breakthrough in one aspect of performance, but dielectric layers are required to be improved to get better performance in leakage current, capacitance density, and transmittance simultaneously in modern electronic devices. Therefore, we optimized the performance of the dielectric layers by using multiple metal oxides. We combined zirconia, yttria, magnesium oxide, alumina, and hafnium oxide with the solution method to find the best combination of these five metal oxides. The physical properties of the multi-component films were measured by atomic force microscopy (AFM), ultraviolet-visible spectrophotometer, and other instruments. The results show that the films prepared by multi-component metal oxides have good transmittance and low roughness. The thicknesses of all films in our experiment are less than 100 nm. Then, metal–insulator–metal (MIM) devices were fabricated. In addition, we characterized the electrical properties of MIM devices. We find that multi-component oxide films can achieve good performances in several aspects. The aluminum-magnesium-yttrium-zirconium-oxide (AMYZOx) group of 0.6 M has the lowest leakage current density, which is 5.03 × 10−8 A/cm2 @ 1.0 MV/cm. The hafnium-magnesium-yttrium-zirconium-oxide (HMYZOx) group of 0.8 M has a maximum capacitance density of 208 nF/cm2. The films with a small thickness and a high capacitance density are very conducive to high integration. Therefore, we believe that multi-component films have potential in the process of dielectric layers and great application prospects in highly integrated electronic devices.

Flexible thin-film transistors with high current-driven capability are of great significance for the next-generation new display technology. The effect of a Cu-Cr-Zr (CCZ) copper alloy source/drain (S/D) electrode on flexible amorphous neodymium-doped indium-zinc-oxide thin-film transistors (NdIZO-TFTs) was investigated. Compared with pure copper (Cu) and aluminum (Al) S/D electrodes, the CCZ S/D electrode changes the TFT working mode from depletion mode to enhancement mode, which is ascribed to the alloy-assisted interface layer besides work function matching. X-ray photoelectron spectroscopy (XPS) depth profile analysis was conducted to examine the chemical states of the contact interface, and the result suggested that chromium (Cr) oxide and zirconium (Zr) oxide aggregate at the interface between the S/D electrode and the active layer, acting as a potential barrier against residual free electron carriers. The optimal NdIZO-TFT exhibited a desired performance with a saturation mobility (μsat) of 40.3 cm2·V-1·s-1, an Ion/Ioff ratio of 1.24×108, a subthreshold swing (SS) value of 0.12 V·decade-1, and a threshold voltage (Vth) of 0.83 V. This work is anticipated to provide a novel approach to the realization of high-performance flexible NdIZO-TFTs working in enhancement mode.

Solution-processed oxide dielectrics are widely studied as alternatives to SiO2, SiNx in thin film transistors for high capacitance and low energy consuming. However, it's still a challenge to achieve high quality of solution-processed oxide dielectrics TFT by low-temperature post-treatment. Here, an effective strategy is proposed to evaluate low temperature solution-processed ZrO2 TFT in terms of uniformity, film density and electrical performance by employing TG/DSC, drop analyzer, XRR and a novel μ-PCD measurement. Particularly, μ-PCD measurement provides valuable information on homogeneity and defect level. The optimized device with ZrNO3 as dielectric precursor and ethyl alcohol as solvent through spin coating process annealed at 200°C shows a saturation mobility of 8.6 cm2V-1S-1, Ion/Ioff ratio about 1.1×106, subthreshold swing about 334 mV/decade with a low leakage current density of 5×10-5 A/cm2 at 10V. This article offers a convenient way for precursor optimization towards low leakage current and high homogeneity solution-processed oxide dielectrics for TFT devices.

Abstract We first verify the critical impact of evaporation on the formation of zigzag hollow cracks by regulating the drying micro-environment of silver nanoparticle film. Uneven evaporation and component segregation contributes to the flows along the surface and inside of droplets. Asymmetric vapor concentration distribution is capable of weakening the surface flow of droplets, thus suppressing the inner compressive stress of nanoparticles and leading to a surface morphology with less cracks. Although defect-free and surface smooth nanoparticle film deposited by a solution-based method remains a big challenge, our work has referential significance to optimize high-quality nanoparticle film with appropriate deposition and curing processes. Moreover, an optimization possibility through the drying micro-environment should be considered in high-end applications due to its enhanced effect on high-resolution patterns.

Over the past few decades, electrohydrodynamic (EHD) printing has proved to be an environmentally friendly, cost-effective and powerful tool in manufacturing electronic devices with a wire width of less than 50 μm. In particular, EHD printing is highly valued for the printing of ultrafine wire-width silver electrodes, which is important in manufacturing large-area, high-resolution micron-scale or even nanoscale structures. In this paper, we compare two methods of surface modification of glass substrate: UV treatment and oxygen plasma treatment. We found that oxygen plasma was better than UV treatment in terms of wettability and uniformity. Secondly, we optimized the annealing temperature parameter, and found that the conductivity of the electrode was the highest at 200 °C due to the smoothing silver electrode and the oxidation-free internal microstructure. Thirdly, we used EHD printing to fabricate silver electrodes on the glass substrate. Due to the decrease of conductivity as a result of the skin effect and the decrease of silver content, we found that driving voltage dropped, line width decreased, and the conductivity of silver line decreased. After the optimization of the EHD printing process, Ag electrode line width and conductivity reached 19.42 ± 0.24 μm and 6.01 × 106 S/m, demonstrating the potential of electro-hydraulic printing in the manufacturing of flexible, wearable, high-density, low-power-consumption electronics.

Flexible and fully transparent thin film transistors (TFT) were fabricated via room temperature processes. The fabricated TFT on the PEN exhibited excellent performance, including a saturation mobility (μsat) of 7.9 cm2/V·s, an Ion/Ioff ratio of 4.58 × 106, a subthreshold swing (SS) of 0.248 V/dec, a transparency of 87.8% at 550 nm, as well as relatively good stability under negative bias stress (NBS) and bending stress, which shows great potential in smart, portable flexible display, and wearable device applications.

Inkjet printing is a non-vacuum, non-contact, low-cost, and direct patterning thin film deposition technique. Compared to traditional processes, it demands less materials and energy, simplifies processing steps and is compatible with the fast fabrication of flexible and large-size devices, thus potential in the application of thin film transistors. In this paper, we have compared the main techniques of inkjet printing, and discussed the formulation of conductive inks, the deposition of high quality electrodes, and the obtaining of high resolution and high performance thin film transistors. Moreover, the faced problems and corresponding solving methods of inkjet printed thin film transistor with low sintering temperature, small line width, short channel, high mobility, and designed structure are summarized by the understanding of the interaction among inkjet printing devices, materials, processes, and the fabrication of transistors, which providing referential significance of the following research effort.

In this paper, we present a high mobility amorphous indium-zinc-oxide (a-IZO) thin film transistor (TFT) based on copper (Cu) source/drain electrodes (S/D) and aluminum oxide (Al2O3) passivation layer (PVL). The mechanism of high mobility for the a-IZO TFT based on Cu S/D with Al2O3 PVL was proposed and experimentally demonstrated. The sputtering of Al2O3 PVL induced a highly conductive channel layer due to the formation of In-rich layer on the back channel. Also, Cu S/D presented Schottky contact behavior compared with Mo S/D which behaved like Ohmic contact. Because the Schottky contact can block leakage current and the highly conductive channel achieved high on-current, the a-IZO TFT based on Cu S/D and Al2O3 PVL performed remarkable saturation mobility up to 412.7 cm2/Vs. This paper presents a feasible way to implement high mobility TFT arrays with Cu electrodes.

Silver nanowire (AgNW) conductive film fabricated by solution processing was investigated as an alternative to indium tin oxide (ITO) in flexible transparent electrodes. In this paper, we studied a facile and effective method by electrodepositing Al2O3 on the surface of AgNWs. As a result, flexible transparent electrodes with improved stability could be obtained by electrodepositing Al2O3. It was found that, as the annealing temperature rises, the Al2O3 coating layer can be transformed from Al2O3·H2O into a denser amorphous state at 150 °C. By studying the increase of electrodeposition temperature, it was observed that the transmittance of the AgNW–Al2O3 composite films first rose to the maximum at 70 °C and then decreased. With the increase of the electrodeposition time, the figure of merit (FoM) of the composite films increased and reached the maximum when the time was 40 s. Through optimizing the experimental parameters, a high-stability AgNW flexible transparent electrode using polyimide (PI) as a substrate was prepared without sacrificing optical and electrical performance by electrodepositing at −1.1 V and 70 °C for 40 s with 0.1 mol/L Al(NO3)3 as the electrolyte, which can withstand a high temperature of 250 °C or 250,000 bending cycles with a bending radius of 4 mm.

Optical detection is of great significance in various fields such as industry, military, and medical treatment, especially ultraviolet (UV) photodetectors. Moreover, as the demand for wearable devices continues to increase, the UV photodetector, which is one of the most important sensors, has put forward higher requirements for bending resistance, durability, and transparency. Tin oxide (SnO2) has a wide band gap, high ultraviolet exciton gain, etc., and is considered to be an ideal material for preparing UV photodetectors. At present, SnO2-based UV photodetectors have a transparency of more than 70% in the visible light region and also have excellent flexibility of 160% tensile strain. Focusing on SnO2 nanostructures, the article mainly summarizes the progress of SnO2 UV photodetectors in flexibility and transparency in recent years and proposes feasible optimization directions and difficulties.

The active layer of metal oxide semiconductor thin film transistor (MOS-TFT) prepared by solution method, with the advantages of being a low cost and simple preparation process, usually needs heat treatment to improve its performance. Laser treatment has the advantages of high energy, fast speed, less damage to the substrate and controllable treatment area, which is more suitable for flexible and large-scale roll-to-roll preparation than thermal treatment. This paper mainly introduces the basic principle of active layer thin films prepared by laser treatment solution, including laser photochemical cracking of metastable bonds, laser thermal effect, photoactivation effect and laser sintering of nanoparticles. In addition, the application of laser treatment in the regulation of MOS-TFT performance is also described, including the effects of laser energy density, treatment atmosphere, laser wavelength and other factors on the performance of active layer thin films and MOS-TFT devices. Finally, the problems and future development trends of laser treatment technology in the application of metal oxide semiconductor thin films prepared by solution method and MOS-TFT are summarized.

Abstract Inkjet-printed silver gate electrode with low electrical resistivity was fabricated by UV curing method. By adjusting the UV curing time and the distance between the samples and UV lamp, the effects of UV curing conditions on the electrical resistivity of the silver films were studied, and the lowest electrical resistivity of 6.69 × 10−8 Ω·m was obtained. Besides, the UV-cured silver films have good adhesion to the glass substrates, with adhesion strength of 4B (ASTM international standard). Our work offered an easy and low temperature approach to fabricate inkjet-printed silver electrodes with low electrical resistivity.

The effect of Si concentration on the electronic and optical properties of Si incorporated SnO2 was investigated by density functional theory. SnO2 maintained the direct bandgap after Si incorporation, and the value of bandgap enlarged as the Si concentration increased. The formation of the Si–O covalent bond could reduce electron losses of Sn atoms that resulted in the decrease of electron concentration of SnO2 through the density of states and charge density analysis. On the basis of the calculation results of the optical properties including the dielectric function, refractive index, reflectivity, absorption, and electron energy-loss spectrum, the values of these parameters were reduced at a low energy region and these curves gradually shifted toward high energy as the Si concentration increased. It suggested that the optical properties of SnO2 could be improved by the Si atom over the infrared and visible spectra.

Amorphous metal oxide has been a popular choice for thin film material in recent years due to its high uniformity. The dielectric layer is one of the core materials of the thin film transistor (TFT), and it affects the ability of charges storage in TFT. There is a conflict between a high relative dielectric constant and a wide band gap, so we solved this problem by using multiple metals to increase the entropy of the system. In this paper, we prepared zirconium-yttrium-aluminum-magnesium-oxide (ZYAMO) dielectric layers with a high relative dielectric constant using the solution method. The basic properties of ZYAMO films were measured by an atomic force microscope (AFM), an ultraviolet-visible spectrophotometer (UV-VIS), etc. It was observed that ZYAMO thin films had a larger optical band when the annealing temperature increased. Then, metal-insulator-metal (MIM) devices were fabricated to measure the electrical properties. We found that the leakage current density of the device is relatively lower and the ZYAMO thin film had a higher relative dielectric constant as the concentration went up. Finally, it reached a high relative dielectric constant of 56.09, while the leakage current density was no higher than 1.63 × 10−6 A/cm2@ 0.5 MV/cm at 1.0 M and 400 °C. Therefore, the amorphous ZYAMO thin films has a great application in the field of high permittivity request devices in the future.

The praseodymium-doped indium-zinc-oxide (PrIZO) thin film transistor (TFT) shows broad application prospects in the new generation of display technologies due to its high performance and high stability. However, traditional device performance evaluation methods need to be carried out after the end of the entire preparation process, which leads to the high-performance device preparation process that takes a lot of time and costs. Therefore, there is a lack of effective methods to optimize the device preparation process. In this paper, the effect of sputtering oxygen partial pressure on the properties of PrIZO thin film was studied, and the quality of PrIZO thin film was quickly evaluated by the microwave photoconductivity decay (µ-PCD) method. The μ-PCD results show that as the oxygen partial pressure increases, the peak first increases and then decreases, while the D value shows the opposite trend. The quality of PrIZO thin film prepared under 10% oxygen partial pressure is optimal due to its low localized defect states. The electric performance of PrIZO TFTs prepared under different oxygen partial pressures is consistent with the μ-PCD results. The optimal PrIZO TFT prepared under 10% oxygen partial pressure exhibits good electric performance with a threshold voltage (Vth) of 1.9 V, a mobility (µsat) of 24.4 cm2·V−1·s−1, an Ion/Ioff ratio of 2.03 × 107, and a subthreshold swing (SS) of 0.14 V·dec−1.

We report the effects of ultraviolet (UV) irradiation and storage on the performance of ZnO-based inverted quantum-dot light-emitting diodes (QLEDs). The effects of UV irradiation on the electrical properties of ZnO nanoparticles (NPs) were investigated. We demonstrate that the charge balance was enhanced by improving the electron injection. The maximum external quantum efficiency (EQE) and power efficiency (PE) of QLEDs were increased by 26% and 143% after UV irradiation for 15 min. In addition, we investigated the storage stabilities of the inverted QLEDs. During the storage period, the electron current from ZnO gradually decreased, causing a reduction in the device current. However, the QLEDs demonstrated improvements in maximum EQE by 20.7% after two days of storage. Our analysis indicates that the suppression of exciton quenching at the interface of ZnO and quantum dots (QDs) during the storage period could result in the enhancement of EQE. This study provides a comprehension of the generally neglected factors, which could be conducive to the realization of high-efficiency and highly storage-stable practical applications.

With the rapid development of flexible electronic devices (especially flexible LCD/OLED), flexible transparent electrodes (FTEs) with high light transmittance, high electrical conductivity, and excellent stretchability have attracted extensive attention from researchers and businesses. FTEs serve as an important part of display devices (touch screen and display), energy storage devices (solar cells and super capacitors), and wearable medical devices (electronic skin). In this paper, we review the recent progress in the field of FTEs, with special emphasis on metal materials, carbon-based materials, conductive polymers (CPs), and composite materials, which are good alternatives to the traditional commercial transparent electrode (i.e., indium tin oxide, ITO). With respect to production methods, this article provides a detailed discussion on the performance differences and practical applications of different materials. Furthermore, major challenges and future developments of FTEs are also discussed.

An environment-friendly inverted indium phosphide red quantum dot light-emitting diode (InP QLED) was fabricated using Mg-doped zinc oxide (ZnMgO) as the electron transport layer (ETL). The effects of ZnMgO ETL on the performance of InP QLED were investigated. X-ray diffraction (XRD) analysis indicated that ZnMgO film has an amorphous structure, which is similar to zinc oxide (ZnO) film. Comparison of morphology between ZnO film and ZnMgO film demonstrated that Mg-doped ZnO film remains a high-quality surface (root mean square roughness: 0.86 nm) as smooth as ZnO film. The optical band gap and ultraviolet photoelectron spectroscopy (UPS) analysis revealed that the conduction band of ZnO shifts to a more matched position with InP quantum dot after Mg-doping, resulting in the decrease in turn-on voltage from 2.51 to 2.32 V. In addition, the ratio of irradiation recombination of QLED increases from 7% to 25% using ZnMgO ETL, which can be attributed to reduction in trap state by introducing Mg ions into ZnO lattices. As a result, ZnMgO is a promising material to enhance the performance of inverted InP QLED. This work suggests that ZnMgO has the potential to improve the performance of QLED, which consists of the ITO/ETL/InP QDs/TCTA/MoO3/Al, and Mg-doping strategy is an efficient route to directionally regulate ZnO conduction bands.

Over the past decade, there have been many reports on solution-processed oxide thin-film transistors (TFTs) with high mobility (even >100 cm2 V−1s−1). However, the capacitance uncertainty of the solution-processed oxide gate dielectrics leads to serious overestimation of the mobility. Here, solution-processed AlOx dielectrics are investigated systematically, and the effect of mobile ions on the frequency-dependent capacitance of the solution-processed AlOx dielectrics is also studied. It was found that the capacitance of the AlOx depends on the frequency seriously when the annealing temperature is lower than 300 °C, and the water treatment causes more seriously frequency-dependent capacitance. The strong frequency-dependent capacitance of the AlOx annealed at 250 or 300 °C is attributed to relaxation polarization of the weakly bound ions in the incompletely decomposed AlOx films. The water treatment introduces a large number of protons (H+) that would migrate to the ITO/AlOx interface under a certain electric field and form an electric double layer (EDL) that has ultrahigh capacitance at low frequency.

High-performance amorphous oxide semiconductor thin film transistors (AOS-TFT) with copper (Cu) electrodes are of great significance for next-generation large-size, high-refresh rate and high-resolution panel display technology. In this work, using rare earth dopant, neodymium-doped indium-zinc-oxide (NdIZO) film was optimized as the active layer of TFT with Cu source and drain (S/D) electrodes. Under the guidance of the Taguchi orthogonal design method from Minitab software, the semiconductor characteristics were evaluated by microwave photoconductivity decay (μ-PCD) measurement. The results show that moderate oxygen concentration (~5%), low sputtering pressure (≤5 mTorr) and annealing temperature (≤300 °C) are conducive to reducing the shallow localized states of NdIZO film. The optimized annealing temperature of this device configuration is as low as 250 °C, and the contact resistance (RC) is modulated by gate voltage (VG) instead of a constant value when annealed at 300 °C. It is believed that the adjustable RC with VG is the key to keeping both high mobility and compensation of the threshold voltage (Vth). The optimal device performance was obtained at 250 °C with an Ion/Ioff ratio of 2.89 × 107, a saturation mobility (μsat) of 24.48 cm2/(V·s) and Vth of 2.32 V.

In this work, we performed a systematic study of the physical properties of amorphous Indium–Gallium–Zinc Oxide (a-IGZO) films prepared under various deposition pressures, O2/(Ar+O2) flow ratios, and annealing temperatures. X-ray reflectivity (XRR) and microwave photoconductivity decay (μ-PCD) measurements were conducted to evaluate the quality of a-IGZO films. The results showed that the process conditions have a substantial impact on the film densities and defect states, which in turn affect the performance of the final thin-film transistors (TFT) device. By optimizing the IGZO film deposition conditions, high-performance TFT was able to be demonstrated, with a saturation mobility of 8.4 cm2/Vs, a threshold voltage of 0.9 V, and a subthreshold swing of 0.16 V/dec.

Nickel oxide (NiO) is a wide band gap semiconductor material that is used as an electrochromic layer or an ion storage layer in electrochromic devices. In this work, the effect of annealing temperature on sol-gel NiO films was investigated. Fourier transform infrared spectroscopy (FTIR) showed that the formation of NiO via decomposition of the precursor nickel acetate occurred at about 300 °C. Meanwhile, an increase in roughness was observed by Atomic force microscope (AFM), and precipitation of a large number of crystallites was observed at 500 °C. X-ray Diffraction (XRD) showed that the NiO film obtained at such a temperature showed a degree of crystallinity. The film crystallinity and crystallite size also increased with increasing annealing temperature. An ultraviolet spectrophotometer was used to investigate the optical band gap of the colored NiO films, and it was found that the band gap increased from 3.65 eV to 3.74 eV with the increase in annealing temperature. An electrochromic test further showed that optical modulation density and coloring efficiency decreased with the increase in crystallite size. The electrochromic reaction of the nickel oxide film is more likely to occur at the crystal interface and is closely related to the change of the optical band gap. An NiO film with smaller crystallite size is more conducive to ion implantation and the films treated at 300 °C exhibit optimum electrochromic behavior.

In this paper, the effects of annealing temperature and other process parameters on spin-coated indium oxide thin film transistors (In2O3-TFTs) were studied. The research shows that plasma pretreatment of glass substrate can improve the hydrophilicity of glass substrate and stability of the spin-coating process. With Fourier transform infrared (FT-IR) and X-ray diffraction (XRD) analysis, it is found that In2O3 thin films prepared by the spin coating method are amorphous, and have little organic residue when the annealing temperature ranges from 200 to 300 °C. After optimizing process conditions with the spin-coated rotating speed of 4000 rpm and the annealing temperature of 275 °C, the performance of In2O3-TFTs is best (average mobility of 1.288 cm2·V−1·s−1, Ion/Ioff of 5.93 × 106, and SS of 0.84 V·dec−1). Finally, the stability of In2O3-TFTs prepared at different annealing temperatures was analyzed by energy band theory, and we identified that the elimination of residual hydroxyl groups was the key influencing factor. Our results provide a useful reference for high-performance metal oxide semiconductor TFTs prepared by the solution method.

The advanced persistent distributed denial-of-service (APDDoS) attack does a serious harm to cyber security. Establishing a mathematical model to accurately predict APDDoS attack on networks is still an important problem that needs to be solved. Therefore, to help us understand the attack mechanisms of APDDoS on networks, this paper first puts forward a novel dynamical model of APDDoS attack on networks. A systematic analysis of this new model shows that the maximum eigenvalue of the networks is a vital factor that determines the success or failure of the attack. What is more, a new sufficient condition for the global stability of attack-free equilibrium is obtained. The global attractivity of attacked equilibrium has also been proved. Eventually, this paper gives some numerical simulations to show the main results.

Tungsten trioxide (WO3) is a wide band gap semiconductor material, which is commonly not only used, but also investigated as a significant electrochromic layer in electrochromic devices. WO3 films have been prepared by inorganic and sol-gel free ammonium tungstate ((NH4)2WO4), with the modification of glycerol using the spin coating technique. The surface tension, the contact angle and the dynamic viscosity of the precursor solutions demonstrated that the sample solution with a 25% volume fraction of glycerol was optimal, which was equipped to facilitate the growth of WO3 films. The thermal gravimetric and differential scanning calorimetry (TG-DSC) analysis represented that the optimal sample solution transformed into the WO3 range from 220 °C to 300 °C, and the transformation of the phase structure of WO3 was taken above 300 °C. Fourier transform infrared spectroscopy (FT-IR) spectra analysis indicated that the composition within the film was WO3 above the 300 °C annealing temperature, and the component content of WO3 was increased with the increase in the annealing temperature. The X-ray diffraction (XRD) pattern revealed that WO3 films were available for the formation of the cubic and monoclinic crystal structure at 400 °C, and were preferential for growing monoclinic WO3 when annealed at 500 °C. Atomic force microscope (AFM) images showed that WO3 films prepared using ammonium tungstate with modification of the glycerol possessed less rough surface roughness in comparison with the sol-gel-prepared films. An ultraviolet spectrophotometer (UV) demonstrated that the sample solution which had been annealed at 400 °C obtained a high electrochromic modulation ability roughly 40% at 700 nm wavelength, as well as the optical band gap (Eg) of the WO3 films ranged from 3.48 eV to 3.37 eV with the annealing temperature increasing.

The urgent demand for transparent flexible electrodes applied in wide bandgap devices has promoted the development of new materials. Silver nanoring (AgNR), known as a special structure of silver nanowire (AgNW), exhibits attractive potential in the field of wearable electronics. In this work, an environmentally friendly glycerol-based cosolvent polyol method was investigated. The Taguchi design was utilized to ascertain the factors that affect the yield and ring diameter of AgNRs. Structural characterization showed that AgNR seeds grew at a certain angle during the early nucleation period. The results indicated that the yield and ring diameter of AgNRs were significantly affected by the ratio of cosolvent. Besides, the ring diameter of AgNRs was also tightly related to the concentration of polyvinylpyrrolidone (PVP). The difference of reducibility between glycerol, water, and ethylene glycol leads to the selective growth of (111) plane and is probably the main reason AgNRs are formed. As a result, AgNRs with a ring diameter range from 7.17 to 42.94 μm were synthesized, and the quantity was increased significantly under the optimal level of factors.

Abstract A very-high color rendering index white organic light-emitting diode (WOLED) based on a simple structure was successfully fabricated. The optimized device exhibits a maximum total efficiency of 13.1 and 5.4 lm/W at 1,000 cd/m2. A peak color rendering index of 90 and a relatively stable color during a wide range of luminance were obtained. In addition, it was demonstrated that the 4,4′,4″-tri(9-carbazoyl) triphenylamine host influenced strongly the performance of this WOLED. These results may be beneficial to the design of both material and device architecture for high-performance WOLED.

Inkjet printing has been proved to be a powerful tool in the cost-effective ambient deposition of functional materials for the fabrication of electronic devices in the past decades. However, restricted by equipment and inks, the feature size of printed dots or lines with conventional inkjet printing is usually limited to several tens of micrometers, which could not fit the requirements for the fabrication of large-area, high-resolution microscale, even nanoscale, structures. Therefore, various technical means were developed for breaking the equipment limits. Here, we report a strategy for realizing ultrashort channels and homogeneous microstructures arrays by a conventional piezoelectric inkjet printing technique without any additional pre-mask process on the substrate. This strategy extends application of piezoelectric inkjet printing technique to biological and technological areas.

In this work, transparent, stable coplanar top-gate thin film transistors (TFTs) with an active layer of neodymium-doped indium oxide and zinc oxide (Nd-IZO) were successfully fabricated on a glass substrate by all sputtering processes. The devices with a post-annealing temperature of 400 °C exhibited good electrical performances with a saturation mobility (μsat) of 4.25 cm2·V−1·S−1, Ion/Ioff ratio about 106, Vth of −0.97 V and SS about 0.34 V/decade. Furthermore, the devices exhibited excellent negative and positive bias stability (NBS, PBS) of only a ΔVth shift of about −0.04 V and 0.05 V after 1 h, respectively. In addition, the devices showed high transparency about 96% over the visible-light region of 400–700 nm, which indicates a great potential in transparent displays.

Tungsten trioxide (WO3) is a wide band gap semiconductor material that is used as an important electrochromic layer in electrochromic devices. In this work, the effects of the annealing temperature on the optical band gap of sol-gel WO3 films were investigated. X-ray Diffraction (XRD) showed that WO3 films were amorphous after being annealed at 100 °C, 200 °C and 300 °C, respectively, but became crystallized at 400 °C and 500 °C. An atomic force microscope (AFM) showed that the crystalline WO3 films were rougher than the amorphous WO3 films (annealed at 200 °C and 300 °C). An ultraviolet spectrophotometer showed that the optical band gap of the WO3 films decreased from 3.62 eV to 3.30 eV with the increase in the annealing temperature. When the Li+ was injected into WO3 film in the electrochromic reaction, the optical band gap of the WO3 films decreased. The correlation between the optical band gap and the electrical properties of the WO3 films was found in the electrochromic test by analyzing the change in the response time and the current density. The decrease in the optical band gap demonstrates that the conductivity increases with the corresponding increase in the annealing temperature.

Ultra-high definition displays have become a trend for the current flat plane displays. In this study, the contact properties of amorphous silicon–tin oxide thin-film transistors (a-STO TFTs) employed with source/drain (S/D) electrodes were analyzed. Ohmic contact with a good device performance was achieved when a-STO was matched with indium-tin-oxide (ITO) or Mo electrodes. The acceptor-like densities of trap states (DOS) of a-STO TFTs were further investigated by using low-frequency capacitance–voltage (C–V) characteristics to understand the impact of the electrode on the device performance. The reason of the distinct electrical performances of the devices with ITO and Mo contacts was attributed to different DOS caused by the generation of local defect states near the electrodes, which distorted the electric field distribution and formed an electrical potential barrier hindering the flow of electrons. It is of significant importance for circuit designers to design reliable integrated circuits with SnO2-based devices applied in flat panel displays.

In this paper, a high-k metal-oxide film (ZrO2) was successfully prepared by a solution-phase method, and whose physical properties were measured by X-ray diffraction (XRD), X-ray reflectivity (XRR) and atomic force microscopy (AFM). Furthermore, indium–gallium–zinc oxide thin-film transistors (IGZO-TFTs) with high-k ZrO2 dielectric layers were demonstrated, and the electrical performance and bias stability were investigated in detail. By spin-coating 0.3 M precursor six times, a dense ZrO2 film, with smoother surface and fewer defects, was fabricated. The TFT devices with optimal ZrO2 dielectric exhibit a saturation mobility up to 12.7 cm2 V−1 s−1, and an on/off ratio as high as 7.6 × 105. The offset of the threshold voltage was less than 0.6 V under positive and negative bias stress for 3600 s.

In this work, we fabricated a high-mobility amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) based on alumina oxide (Al 2 O 3 ) passivation layer (PVL) and copper (Cu) source/drain electrodes (S/D). The mechanism of the high mobility for a-IGZO TFT was proposed and experimentally demonstrated. The conductivity of the channel layer was significantly improved due to the formation of metallic In nanoparticles on the back channel during Al 2 O 3 PVL sputtering. In addition, Ar atmosphere annealing induced the Schottky contact formation between the Cu S/D and the channel layer caused by Cu diffusion. In conjunction with high conductivity channel and Schottky contact, the a-IGZO TFT based on Cu S/D and Al 2 O 3 PVL exhibited remarkable mobility of 33.5–220.1 cm 2 /Vs when channel length varies from 60 to 560 μ m. This work presents a feasible way to implement high mobility and Cu electrodes in a-IGZO TFT, simultaneously.

In this paper, an alumina-zirconia (Al2O3-ZrO2) nanolaminate dielectric was fabricated by spin-coating and the performance was investigated. It was found that the properties of the dielectric can be adjusted by changing the content of Al2O3/ZrO2 in nanolaminates: when the content of Al2O3 was higher than 50%, the properties of nanolaminates, such as the optical energy gap, dielectric strength (Vds), capacitance density, and relative permittivity were relatively stable, while the change of these properties became larger when the content of Al2O3 was less than 50%. With the content of ZrO2 varying from 50% to 100%, the variation of these properties was up to 0.482 eV, 2.12 MV/cm, 135.35 nF/cm2, and 11.64, respectively. Furthermore, it was demonstrated that the dielectric strength of nanolaminates were influenced significantly by the number (n) of bilayers. Every increment of one Al2O3-ZrO2 bilayer will enhance the dielectric strength by around 0.39 MV/cm (Vds ≈ 0.86 + 0.39n). This could be contributed to the amorphous alumina which interrupted the grain boundaries of zirconia.

The characteristics of Cu alloy (0.3 wt. % Cr, 0.2 wt. % Zr) thin film deposited by direct current (DC) magnetron sputtering deposition were investigated. The conductivity and adhesion of the Cu-0.3%Cr-0.2%Zr films were optimized by increasing the sputter power to 150 W and reducing the sputter pressure to 2 mTorr. With an annealing process (at 300 °C for 1 h in argon ambient atmosphere), the resistivity of the alloy film decreased from 4.80 to 2.96 μΩ·cm, and the adhesion classification increased from 2B to 4B on glass substrate. X-ray photoelectron spectroscopy (XPS) analysis showed that Cr aggregated toward the surface of the film and formed a self-protection layer in the annealing process. Transmission electron microscopy (TEM) indicated the aggregation and migration of Cr in the annealing process. A further X-ray diffraction (XRD) analysis showed that Cu2O appeared when the annealing temperature reached above 350 °C, which accounts for the increase of the resistivity. Based on Al2O3 and SiO2 substrate surfaces, the Cu-0.3%Cr-0.2%Zr film also showed high conductivity and adhesion, which has a potential in the application of Cu gate electrodes for thin film transistor (TFT).

Recently, amorphous indium-gallium-zinc-oxide thin film transistors (a-IGZO TFTs) with inkjet printing silver source/drain electrodes have attracted great attention, especially for large area and flexible electronics applications. The silver ink could be divided into two types: one is based on silver nanoparticles, and the other is silver salt ink. Organic materials are essential in the formulation of nanoparticle ink as a strong disperse stabilizer to prevent agglomeration of silver particles, but will introduce contact problems between the silver electrodes and the a-IGZO active layer after annealing, which is difficult to eliminate and leads to poor device properties. Our experiment is aimed to reduce this effect by using a silver salt ink without stabilizer component. With optimized inkjet printing conditions, the high performance of a-IGZO TFT was obtained with a mobility of 4.28 cm2/V·s and an on/off current ratio over 106. The results have demonstrated a significant improvement for a-IGZO TFTs with directly printed silver electrodes. This work presents a promising platform for future printed electronic applications.