Highly Crystalline Soluble Acene Crystal Arrays for Organic Transistors: Mechanism of Crystal Growth During Dip‐Coating

Abstract

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).

Organic Field-Effect Transistor: Device Physics, Materials, and Process

“…Under appropriate rates of solution supply and solvent evaporation, a stationary gradient of concentration is formed within the meniscus, which gives rise to directional crystallization [58]. Dip-coating is another technique to give a better thin-film alignment in solution-processed devices [59,60]. This process can be controlled by the substrate lift rate, solvent evaporation, and capillary flow.…”

Determination of crystal orientation in organic thin films using optical microscopy

“…Meniscus guided techniques such as zone casting [24], dipcoating [25], or modified edge casting [10] allow to grow single crystalline layers of organic semiconductors. PLM, however, fails to identify their in-plane crystal orientation.…”

Few‐Volt Operation of Printed Organic Ferroelectric Capacitor

“…Single crystals of organic semiconductor thin fi lms composed of small molecules have been obtained by several sophisticated techniques, such as dip coating, [ 14,15 ] inkjet printing, [ 16 ] and solution shearing. [ 17 ] Note that solution shearing differs from similar methods [ 18 ] such as blade coating, which is used to fabricate amorphous fi lms composed of ferroelectric [ 19 ] or organic light-emitting diode materials.…”