A new
organic small-molecule family comprising tetracyanoquinodimethane-substituted
quinoidal dithioalky(SR)terthiophenes (DSTQs) (DSTQ-6 (1); SR = SC6H13, DSTQ-10 (2); SR = SC10H21, DSTQ-14 (3); SR = SC10H21) was synthesized and contrasted with a nonthioalkylated
analogue (DRTQ-14 (4); R = C14H29). The physical, electrochemical, and electrical properties
of these new compounds are thoroughly investigated. Optimized geometries
obtained from density functional theory calculations and single-crystal
X-ray diffraction reveal the planarity of the SR-containing DSTQ core. DSTQs pack in a slipped π–π
stacked two-dimensional arrangement, with a short intermolecular stacking distance
of 3.55 Å and short intermolecular S···N contacts
of 3.56 Å. Thin-film morphological analysis by grazing incident
X-ray diffraction reveals that all DSTQ molecules are
packed in an edge-on fashion on the substrate. The favorable molecular
packing, the high core planarity, and very low lowest unoccupied molecular
orbital (LUMO) energy level (−4.2 eV) suggest that DSTQs could be electron-transporting semiconductors. Organic field-effect
transistors based on solution-sheared DSTQ-14 exhibit
the highest electron mobility of 0.77 cm2 V–1 s–1 with good ambient stability, which is the
highest value reported to date for such a solution process terthiophene-based
small molecular semiconductor. These results demonstrate that the
device performance of solution-sheared DSTQs can be improved
by side chain engineering.
Four soluble dialkylated tetrathienoacene (TTAR)-based small molecular semiconductors featuring the combination of a TTAR central core, π-conjugated spacers comprising bithiophene (bT) or thiophene (T), and with/without cyanoacrylate (CA) end-capping moieties are synthesized and characterized. The molecule DbT-TTAR exhibits a promising hole mobility up to 0.36 cm 2 V −1 s −1 due to the enhanced crystallinity of the microribbon-like films. Binary blends of the p-type DbT-TTAR and the n-type dicyanomethylene substituted dithienothiophene-quinoid (DTTQ-11) are investigated in terms of film morphology, microstructure, and organic field-effect transistor (OFET) performance. The data indicate that as the DbT-TTAR content in the blend film increases, the charge transport characteristics vary from unipolar (electron-only) to ambipolar and then back to unipolar (hole-only). With a 1:1 weight ratio of DbT-TTAR/DTTQ-11 in the blend, well-defined pathways for both charge carriers are achieved and resulted in ambipolar transport with high hole and electron mobilities of 0.83 and 0.37 cm 2 V −1 s −1 , respectively. This study provides a viable way for tuning microstructure and charge carrier transport in small molecules and their blends to achieve high-performance solution-processable OFETs.
A nanocomposite comprising FePt nanoparticles and hollow mesoporous silica nanospheres has been fabricated for MRI, NIR photothermal therapy and combined chemo-/thermotherapy.
Three new solution‐processable organic semiconductors (1–3) are synthesized and characterized for p‐type organic field effect transistors (OFETs). The backbone of these small molecules is modified by expanding the central core conjugation from thienothiophene (TT) to dithienothiophene (DTT) and tetrathienoacene (TTA), which are end‐capped with soluble β‐substituted alkyl chains dithienothiophenes (DTTR) to generate DTTR‐TT (1), DTTR‐DTT (2), and DTTR‐TTA (3). The highest mobility of 0.016 cm2 V−1 s−1 is achieved using solution‐sheared DTTR‐TTA film due to the extended conjugated TTA core, which enhances the intermolecular interaction and generates an efficient percolation for the OFET channel. Solution blending of crystalline DTTR‐TT small molecules with oriented‐packing polymer dithienothiophene‐thioalkylbithiophene (PDTT‐SBT) polymer leads to significantly enhanced mobilities from 0.0009 up to 0.22 cm2 V−1 s−1, occurring at an optimized 30% DTTR‐TT composition in the blend. Hole mobility of 30% DTTR‐TT blend is 0.22 cm2 V−1 s−1 which is higher than pristine small molecule DTTR‐TT (0.0009 cm2 V−1 s−1) and polymer PDTT‐SBT (0.067 cm2 V−1 s−1), respectively. An efficient strategy to enhance the mobility of small molecule DTTR‐TT by blending with easily synthesizable PDTT‐SBT polymer is reported.
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