Anthracenedicarboximide-based semiconductors for air-stable, n-channel organic thin-film transistors: materials design, synthesis, and structural characterization?

Journal of Materials Chemistry Pub Date: 2011-12-22 DOI: 10.1039/C1JM14713G

Abstract

A family of six n-channel organic semiconductors (1–6) based on the N,N′-dialkyl-2,3:6,7-anthracenedicarboximide (ADI) core was synthesized and characterized. These new semiconductors are functionalized with n-octyl (-n-C8H17), 1H,1H-perfluorobutyl (-n-CH2C3F7), cyano (–CN), and bromo (–Br) substituents, which results in wide HOMO and LUMO energy variations (～1 eV) but negligible optical absorbance (λmax = 418–436 nm) in the visible region of the solar spectrum. Organic thin-film transistors (OTFTs) were fabricated via semiconductor vapor-deposition, and the resulting devices exhibit exclusively electron transport with good carrier mobilities (μe) of 10?3 to 0.06 cm2 V?1 s?1. Within this semiconductor family, cyano core-substitution plays a critical role in properly tuning the LUMO energy to enable good electron transport in ambient conditions while maintaining a low level of ambient doping (i.e., low Ioff). Core-cyanated ADIs 3 and 6 exhibit air-stable TFT device operation with electron mobilities up to 0.04 cm2 V?1 s?1 in air. Very high current on/off ratios of >107 are measured with positive threshold voltages (Vth = 5–15 V) and low off currents (Ioff = 10?9 to 10?12 A). Single-crystal structures of N,N′-1H,1H-perfluorobutyl ADIs 5 and 6 exhibit slipped-stack cofacial crystal packing with close π–π stacking distances of ～3.2 ?. Additionally, close intermolecular interactions between imide-carbonyl oxygen and anthracene core-hydrogen are identified, which lead to the assembly of highly planar lamellar layers. Analysis of the air-stability of 1–6 thin films suggests that air-stability is mainly controlled by the LUMO energetics, and an electrochemical threshold of Ered1 = ?0.3 to ?0.4 V is estimated to stabilize n-channel transport in this family of materials.

Graphical abstract: Anthracenedicarboximide-based semiconductors for air-stable, n-channel organic thin-film transistors: materials design, synthesis, and structural characterization
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