JOURNAL OF MATERIALS CHEMISTRY, cilt.22, ss.4459-4472, 2012 (SCI İndekslerine Giren Dergi)
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 (similar to 1 eV) but negligible optical absorbance (lambda(max) 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 (mu(e)) of 10(-3) to 0.06 cm(2) 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 I-off). Core-cyanated ADIs 3 and 6 exhibit air-stable TFT device operation with electron mobilities up to 0.04 cm(2) V-1 s(-1) in air. Very high current on/off ratios of >10(7) are measured with positive threshold voltages (V-th 5-15 V) and low off currents (I-off = 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 pi-pi stacking distances of similar to 3.2 angstrom. 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 E-red1 = -0.3 to -0.4 V is estimated to stabilize n-channel transport in this family of materials.