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Oxide semiconductors have been considered as promising channel materials for thin-film transistors (TFTs). However, device reliability against negative-bias illumination stress (NBIS) remains a critical issue that hampers further applications. In this article, the effect of the bandgap widening on the NBIS stability of the oxide TFTs is investigated by simply incorporating the wide bandgap Ga2O3 into In2O3. It is found that there is a tradeoff between the mobility and the NBIS stability. When the Ga2O3 concentration increases from 10 wt% to 45 wt%, the mobility decreases from 22.9 to 5.5 cm2·V−1·s−1, while the ${V}_{ \mathrm{\scriptscriptstyle ON}}$ shift ( $\Delta {V}_{ \mathrm{\scriptscriptstyle ON}}$ ) under 3600 s NBIS improves from −17.8 to −1.6 V. The great improvement of the NBIS stability with increasing Ga2O3 concentration is ascribed to the bandgap widening. After incorporating a certain amount of Ga2O3 into In2O3, the energy difference between the conduction band minimum (CBM) and the ${V}_{O}$ state is larger than the maximum photon energy of the white LED, resulting in lesser sensitivity to the incident white light.

Light-emitting field-effect transistors (LETs) have drawn much attention for their special capability of combining switching and electroluminescence capacity in a single device. Herein, we report a colour-saturated, high-efficiency red quantum-dot hybrid light-emitting field-effect transistor (QD-HLET) with a solution-processed InScO/ZnO-nanoparticle heterojunction channel layer and a deep-level organic hole transport layer (HLT). The red QD-HLET exhibits a field-effect mobility of 3.1 cm2 V−1 s−1 with an on/off ratio of ∼105, a maximum brightness of 145 000 cd m−2 with a peak external quantum efficiency (EQE) of 22.8% and low efficiency roll-off (an EQE of 17.0% at a brightness of 100 000 cd m−2). In addition, the operating stability of the HLET is investigated by monitoring the time-dependent change in the brightness of the QD-HLET under various VGS, while an operational lifetime of more than 153 000 hours at 100 cd m−2 is achieved. A comprehensive study on the electrical and optical characteristics of the red QD-HLET under different operation modes is conducted, and an operation model is proposed.

Stretchable/wearable capacitive strain sensors are crucial for e-skins to detect physical and physiological signals. However, the fabrication of large-sized, undamaged uniform electrodes with high stretchability by a simple preparation process is still a challenge. In this paper, a capacitive strain sensor based on stretchable vertical graphene (VGr) electrodes is fabricated using a simple chemical peeling (CP) method. The maximum stretch of the sensor is ∼80% with a gauge factor of around 0.97. Furthermore, it exhibits a unique stress direction recognizing ability, making it capable of converting digital codes, such as the Morse code. It is found that the high stretchability of VGr stems from the zigzag cracks and bridging effect of branched VGr nanowalls.

Amorphous oxide semiconductors are promising for their use in thin-film transistor (TFT) devices due to their high carrier mobility and large-area uniformity. However, their commercialization is limited by the negative gate bias stress experienced under continuous light illumination. Here, we report an approach to improve the negative bias illumination stress (NBIS) stability of amorphous oxide semiconductors TFTs by using lanthanide-doped indium oxide semiconductors as the channel layer. The effect of different lanthanide dopants on performances of solution-processed Ln:In2O3 TFTs are investigated. All lanthanides exhibit strong suppression of oxygen vacancy, which shift the Von from −13.5 V of pure In2O3 TFT to −1~1 V of Ln:In2O3 TFTs (except Ce). However, only Pr:In2O3 and Tb:In2O3 TFTs exhibit much better NBIS stability with same ΔVon of −3.0 V, compared to much higher ΔVon of −7.9~−15.6 V for other Ln:In2O3 TFTs. Our comprehensive study reveals that praseodymium and terbium act as a blue light down-conversion medium with low charge transfer transition energy for lowing photosensitivity of oxide semiconductors.

Inkjet-printed thin-film transistors (TFTs) for active-matrix light-emitting diode display are drawing much attention for the advantages of low material waste and simple fabrication processes without vacuum deposition and photolithography steps. Herein, for the first time, solution-processed quantum-dot light-emitting diode (QLED) array displays driven with the inkjet-printed oxide TFT backplane were realized and demonstrated using a general "solvent printing" method. To suppress nanopore formation in the thick oxide films, carbon-free aqueous inks were employed for gate dielectrics. No nanopore was found in the whole 120 nm-thick gate dielectrics. However, compared to the organic inks, the aqueous inks have very low viscosity, resulting in uncontrollable ink spreading especially in transline printing. The ink easily shrinks on the low-surface-energy area and spreads on the high-surface-energy area, leading to serious uniformity problems (the upper lines even break at the top of underlying lines). To solve the problem, a "solvent printing" method was employed to form coffee-line surface-energy patterns, which were uniform without shape distortion. The surface-energy patterns can restrain the ink spreading and tune the morphology of the printed films. As a result, multilayer TFT arrays with ideal shapes were achieved. The mobilities of the printed top-gate TFTs in the backplane array were 3.13 ± 0.87 cm2 V-1 s-1 for switching TFTs and 2.22 ± 0.38 cm2 V-1 s-1 for driving TFTs. Finally, an active-matrix red QLED character display based on the printed oxide TFT backplane and solution-processed QLEDs was demonstrated. The "solvent printing" method opens a general route for inkjet-printed multilayer electronic devices.

It is difficult to implement high-resolution layer-to-layer alignment by direct inkjet printing because of the limitation of position accuracy of the common inkjet printer. The poor alignment of conventional printers generally causes large parasitic overlap capacitances between the gate and source/drain (S/D) of thin-film transistors (TFTs), which degrades device operating speeds. In this paper, a self-aligned method was proposed to minimize the parasitic overlap capacitance. In this method, a hydrophobic fluoropolymers (Cytop) coffee stripe prepared by inkjet printing was utilized to define the gate electrodes, and to dewet deposited ink droplet for self-aligned S/D electrodes. This kind of inkjet-printed self-aligned TFTs with In0.95Sc0.05Ox channel layer have a parasitic overlap capacitance as small as 0.31–0.45 pF. The TFTs in array exhibited an on/off ratio larger than $\textsf {10}^{\textsf {7}}$ and a maximum saturation mobility of $\textsf {4.63}\,\,\textsf {cm}^{\textsf {2}}\,\,\textsf {V}^{-\textsf {1}}\textsf {s}^{-\textsf {1}}$ .

The fully inkjet-printed top-gate metal–oxide thin-film transistors (TFTs) with excellent electrical performance are realized with the gate dielectric layer of scandium zirconium oxide (Sc1Zr1O x ). It is found that adding of nitrate-based scandium oxide (ScO x ) precursor into the chloride ligand-based zirconium oxide (ZrO x ) precursor will reduce the corrosivity of the mixed solution, and the incorporation of Zr ions into ScO x will suppress the hydrogen-ion migration and eliminate the acceptor-like traps in pure ScO x . The fully printed indium gallium oxide (InGaO) TFTs based on Sc1Zr1O x dielectric exhibited an average mobility of 10.8 cm $^{{2}} \text{V}^{\vphantom {R^{'}}-{1}} \cdot \text{s}^{-{1}}$ , a highest mobility of 12.9 cm $^{{2}} \cdot \text{V}^{-{1}} \cdot \text{s}^{-{1}}$ , negligible hysteresis, and excellent stability under both the negative and positive bias stresses. In addition, a resistor-loaded inverter was fabricated using a fully printed InGaO TFT, which exhibited the full swing characteristics and a maximum gain of 5 at 2 V.

Precise characterization of the mechanical properties of polymeric microneedles is crucial for their successful penetration into skin and delivery of the loaded active ingredients. However, most available strategies for this purpose are based on compression of the whole patch, which only provide the average rupture force of the needles and can not give information on the variations across individual microneedles in the patch. In this study, we determined the mechanical strength of individual microneedles of two types of hyaluronic acid microneedles with or without loaded model drugs using a micromanipulation technique. The applied force as a function of displacement of the microneedles was recorded, which was used to determine the rupture displacement, rupture force, and then to derive and calculate normal stress-deformation curve, rupture stress and Young's modulus of individual microneedles. The obtained data suggest that the molecular weight of the polymer and the loading of drug into the microneedles can significantly affect the rupture behavior and mechanical properties of the microneedles, which provides a foundation for preparing sufficiently strong microneedles for controlled drug delivery.

Light-emitting field-effect transistors (LEFETs) have attained great attention due to their special characteristics of both the switching capacity and the electroluminescence capacity. However, high-performance LEFETs with high mobility, high brightness, and high efficiency have not been realized due to the difficulty in developing high electron and hole mobility materials with suitable band structures. In this paper, quantum dot hybrid LEFETs (QD-HLEFETs) combining high-luminous-efficiency quantum dots (QDs) and a solution-processed scandium-incorporated indium oxide (Sc:In2O3) semiconductor were demonstrated. The red QD-HLEFET showed high electrical and optical performance with an electron mobility of 0.8 cm2 V–1 s–1, a maximum brightness of 13 400 cd/m2, and a maximum external quantum efficiency of 8.7%. The high performance of the QD-HLEFET is attributed to the good energy band matching between Sc:In2O3 and QDs and the balanced hole and electron injection (less exciton nonradiative recombination). In ...

Over the past decade, there have been many reports on solution-processed oxide thin-film transistors (TFTs) with high mobility (even &gt, 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.

Cu–10Ni–3Al–0.8Si alloy exhibited desirable physical and mechanical properties and wear resistance for bearing applications. An electrical conductivity of 18.1% IACS, hardness of 309.3 HV, tensile strength of 1004.2 MPa, coefficient of friction of 0.58 and volume wear rate of 4.69×10 -6 mm 3 /mm were obtained with over-aged sample. Adhesion and oxidation were observed to be the two main mechanisms under dry wear condition. The wear resistance of the experimental alloy increased with aging time until the over-aging stage due to the increment of micro-hardness. Adhesion was observed to be the dominant wear mechanism for the cold-rolled sample while tribo-oxidation dominated for the over-aged sample. The latter was attributed to the effect of precipitates on the mechanically mixed layer of the wear sample.

The design and synthesis of three n-type conjugated polymers based on a naphthalene diimide-thiophene skeleton are presented. The control polymer, PNDI-2HD, has two identical 2-hexyldecyl side chains, and the other polymers have different alkyl side chains; PNDI-EHDT has a 2-ethylhexyl and a 2-decyltetradecyl side chain, and PNDI-BOOD has a 2-butyloctyl and a 2-octyldodecyl side chain. These copolymers with different alkyl side chains exhibit higher melting and crystallization temperatures, and stronger aggregation in solution, than the control copolymer PNDI-2HD that has the same side chain. Polymer solar cells based on the electron-donating copolymer PTB7-Th and these novel copolymers exhibit nearly the same open-circuit voltage of 0.77 V. Devices based on the copolymer PNDI-BOOD with different side chains have a power-conversion efficiency of up to 6.89%, which is much higher than the 4.30% obtained with the symmetric PNDI-2HD. This improvement can be attributed to the improved charge-carrier mobility and the formation of favorable film morphology. These observations suggest that the molecular design strategy of incorporating different side chains can provide a new and promising approach to developing n-type conjugated polymers.