Morphological Regulation of Printed Low-Temperature Conductive Ink.

The unbalanced evaporation of solvents in low-temperature sintered inks for printed electronics leads to a series of problems in the actual printing process, including printed pattern distortion, surface cracking, and the coffee ring effect, which has become a serious obstacle to this technique. Here, we present a comprehensive investigation of the influence of the solvent composition, environmental, and sintering conditions on the complicated pattern formation process of reactive silver inks. The results first showed that only inks with a certain wettability of solvents could form well-defined patterns. Then, the solvent composition and ambient humidity can be adjusted to balance the nonequilibrium evaporative flow within the liquid and thus to obtain a flat liquid film. Combined with the rapid UV sintering process, the particle size, porosity, and roughness could be controlled to produce dense and homogeneous silver films. Finally, we successfully printed silver electrodes with a smooth and dense surface (Rqs ∼ 21 nm in 0.8 × 0.8 mm2 area and less than 1% porosity) under an optimized relative humidity (RH) of 50-60% at room temperature with the solvent composition of IPA (isopropanol)/2,3-BD (2,3-butanediol) = 8:2. In addition, we also demonstrated high-performance Pr-IZO (praseodymium-doped indium-zinc oxide) thin film transistors (TFTs) with a mobility (µsat) of 2.14 cm2/V/s and Ion/Ioff ratio of over 107 using source-drain electrodes printed under optimized conditions.

High-Stability Silver Nanowire-Al2O3 Composite Flexible Transparent Electrodes Prepared by Electrodeposition.

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.