Role of Polymorphism and Thin-Film Morphology in Organic Semiconductors Processed by Solution Shearing

Abstract

Organic semiconductors (OSCs) are promising materials for cost-effective production of electronic devices because they can be processed from solution employing high-throughput techniques. However, small-molecule OSCs are prone to structural modifications because of the presence of weak van der Waals intermolecular interactions. Hence, controlling the crystallization in these materials is pivotal to achieve high device reproducibility. In this perspective article, we focus on controlling polymorphism and morphology in small-molecule organic semiconducting thin films deposited by solution-shearing techniques compatible with roll-to-roll systems. Special attention is paid to the influence that the different experimental deposition parameters can have on thin films. Further, the main characterization techniques for thin-film structures are reviewed, highlighting the in situ characterization tools that can provide crucial insights into the crystallization mechanisms.

Addition of the Lewis Acid Zn(C6F5)2 Enables Organic Transistors with a Maximum Hole Mobility in Excess of 20 cm2 V−1 s−1

“…The in‐plane anisotropic variation can be used to estimate the distortion in the ab ‐plane and the change in intermolecular arrangement; Zn(C 6 F 5 ) 2 is found to increase the lattice parameter along [010] b ‐axis and, in order to keep constant (11L) spacing, decrease the lattice parameter along [100] a ‐axis, compressing the a ‐axis in‐plane lattice by ≈1%. Because the C 8 ‐BTBT herringbone motif—similar to rubrene—prefers charge transport between π‐stacking along the a ‐axis, we conclude that such compression may shorten the π–π spacing and benefit charge transport (Figure S8, Supporting Information) . Similar minor changes introducing in‐plane structure polymorphs have been previously reported .…”

Recent Advances in the Bias Stress Stability of Organic Transistors

“…Solution‐processed OSC films typically have inferior molecular ordering and a large number of grain boundaries, which can both generate a higher density of deep localized states when compared to single‐crystalline semiconductor films . Kalb et al compared the bias stress stabilities of small‐molecule OSC films with various crystalline morphologies, i.e., single crystals grown via physical vapor deposition and polycrystalline films grown via thermal evaporation ( Figure a,b) .…”

On the Role of Contact Resistance and Electrode Modification in Organic Electrochemical Transistors

“…Furthermore, improved electrode wetting in the Au:MBT:P‐90 devices likely corresponds to the improved thin‐film formation in the channel (Figure S6, Supporting Information), thereby contributing to overall improvement in MBT‐treated OECTs. Additionally, the improved surface wetting may also impact OSC crystallinity . We therefore used X‐ray diffraction (XRD) to investigate the Au:P‐90, Au:MBT:P‐90, and Au:PFBT:P‐90 thin‐films.…”