Modulated intermolecular electrostatic interaction and morphology transition in squarylium dyes based organic field-effect transistors

A series of indolium squarine dyes were studied as air-stable semiconductors in organic field-effect transistors. By modulating substituted groups and structural rigidity, a mobility of 4.8 × 10−3 cm2/Vs was achieved in solution processed device and the highest mobility of 0.2 cm2/Vs was obtained in single crystal devices. By structural analysis and theoretical calculation, crystal packing mode was found to be associated with the electrostatic attraction and repulsion between positive and negative charge centers of the molecule. This electrostatic interaction drove the spontaneous intermolecular ordering in the film, and resulted in performance enhancement for ISQ transistors. Quantitative research between mobility and the area of polycrystalline regions revealed the dependence of transport ability on the continuity and uniformity of the crystalline phase.

Graphical abstractThe intermolecular electrostatic interaction and transistor of ISQ compounds.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We fabricated air-stable field-effect transistors based on a series of indolium squarine dyes. ► Packing configuration in crystal was affected by intermolecular electrostatic interaction. ► Increased device performance was observed accompanied with the crystallization of film after annealing. ► The highest mobility is 0.2 cm2/Vs. ► The morphology and performance could be modulated by the design of side groups.