The preparation of uniform large-area highly crystalline organic semiconductor thin films that show outstanding carrier mobilities remains a challenge in the field of organic electronics, including organic field-effect transistors. Quantitative control over the drying speed during dip-coating permits optimization of the organic semiconductor film formation, although the kinetics of crystallization at the air–solution–substrate contact line are still not well understood. Here, we report the facile one-step growth of self-aligning, highly crystalline soluble acene crystal arrays that exhibit excellent field-effect mobilities (up to 1.5 cm V⁻¹ s⁻¹) via an optimized dip-coating process. We discover that optimized acene crystals grew at a particular substrate lifting-rate in the presence of low boiling point solvents, such as dichloromethane (b.p. of 40.0 °C) or chloroform (b.p. of 60.4 °C). Variable-temperature dip-coating experiments using various solvents and lift rates are performed to elucidate the crystallization behavior. This bottom-up study of soluble acene crystal growth during dip-coating provides conditions under which one may obtain uniform organic semiconductor crystal arrays with high crystallinity and mobilities over large substrate areas, regardless of the substrate geometry (wafer substrates or cylinder-shaped substrates).

One-, two-, and three-dimensional microstructures with dispersed silver nanoparticles are fabricated by a combination of photopatterning and thermal treatment from a silver salt containing photosensitive epoxy resin. Ultraviolet photo-irradiation and subsequent thermal treatment are combined to control the rate of silver salt reduction, the size and the arrangement of nanoparticles, as well as the reticulation of the epoxy resin. This approach allows the creation of high resolution 1-, 2-, and 3D patterns containing silver nanoparticles, with a homogeneous distribution of nanoparticles regardless of the irradiated area.

Although significant progress has been made in the development of vacuum-deposited small-molecule organic light-emitting diodes (OLEDs), one of the most desired research goals is still to produce flexible displays by low-cost solution processing. The development of solution-processed OLEDs based on small molecules could potentially be a good approach but no intensive studies on this topic have been conducted so far. To fabricate high-performance devices based on solution-processed small molecules, the underlying nature of the produced films and devices must be elucidated. Here, the distinctive characteristics of solution-processed small-molecule films and devices compared to their vacuum-deposited counterparts are reported. Solution-processed blue OLEDs show a very high luminous efficiency (of about 8.9 cd A^–1) despite their simplified structure. A better hole-blocking and electron-transporting layer is essential for achieving high-efficiency solution-processed devices because the solution-processed emitting layer gives the devices a better hole-transporting capability and more electron traps than the vacuum-deposited layer. It is found that the lower density of the solution-processed films (compared to the vacuum-deposited films) can be a major cause for the short lifetimes observed for the corresponding devices.

A novel photosensitive carbon nanotube (CNT) paste based on an acrylated single-walled carbon nanotube (ac-SWNT), a cross-linking agent, and a photoinitiator has been prepared. Unlike the conventional photosensitive CNT pastes reported to date, our photosensitive paste system does not use a polymeric binder for the photopolymerization following UV exposure because the ac-SWNT itself has cross-linkable groups. Therefore, the subsequent firing process can be performed at relatively low temperatures and the residue of the organic vehicle in the SWNT pattern is minimized after firing. The ac-SWNT was synthesized from the reaction between carboxylated SWNT (ca-SWNT) and methacryloyl chloride in the presence of base, and its structure was characterized by Fourier transform infrared, Raman, and X-ray photoelectron spectroscopy. After UV exposure and development with N,N-dimethyl formamide a pattern with a resolution of 8 µm was obtained from the photosensitive CNT paste, which was then fired at 300 °C to give a clear SWNT pattern. When the photosensitive CNT paste was used for the fabrication of a cathode emitter for field emission displays, the CNT pattern emitted electrons under an applied electrical field with emission characteristics comparable with those obtained with screen-printing from conventional CNT pastes. Therefore, such a photosensitive paste for fabricating SWNT patterns can be used in the production of field-emission displays and in future device integration requiring carbon nanotubes, because it provides large-area patterning of SWNT with high stability and uniformity.