Band Engineering and Majority Carrier Switching in Isostructural Donor-Acceptor Complexes DPTTA-F X TCNQ Crystals (X = 1, 2, 4).

Three isostructural donor-acceptor complexes DPTTA-F X TCNQ (X = 1, 2, 4) are investigated experimentally and theoretically. By tuning the number of F atoms in the acceptor molecules, the resulting complexes display a continuous down shift of the valence band maximum, conducting band minimum, and optical bandgap. The majority carriers convert from hole (DPTTA-F1TCNQ), balanced hole, and electron (DPTTA-F2TCNQ) to electron (DPTTA-F4TCNQ). This result shows that band engineering can be realized easily in the donor-acceptor complex systems by tuning the electron affinity of the acceptor. The bandgaps of these three complexes vary from 0.31 to 0.41 eV; this narrow bandgap feature is crucial for achieving high thermoelectric performance and the unintentional doping in DPTTA-F4TCNQ leads to the effective suppression of the bipolar cancelling effect on the Seebeck coefficient and the highest power factor.

Tris(S,S-dioxide)-trithiasumanene: strong fluorescence and cocrystal with 1,2,6,7,10,11-hexabutoxytriphenylene.

Thiophene rings in trithiasumanene (1) are oxidized regioselectively to form tris(S,S-dioxide)-trithiasumanene (3). Compound 3 displays strong indigo fluorescence in both solution and the solid state, and forms a 1 : 1 cocrystal with HBT to give a yellow emission in crystalline form.

Efficient ambipolar transport properties in alternate stacking donor-acceptor complexes: from experiment to theory.

Comprehensive investigations of crystal structures, electrical transport properties and theoretical simulations have been performed over a series of sulfur-bridged annulene-based donor-acceptor complexes with an alternate stacking motif. A remarkably high mobility, up to 1.57 cm(2) V(-1) s(-1) for holes and 0.47 cm(2) V(-1) s(-1) for electrons, was obtained using organic single crystal field-effect transistor devices, demonstrating the efficient ambipolar transport properties. These ambipolar properties arise from the fact that the electronic couplings for both holes and electrons have the same super-exchange nature along the alternate stacking direction. The magnitude of super-exchange coupling depends not only on the intermolecular stacking distance and pattern, but also the energy level alignments between the adjacent donor-acceptor moieties. The concluded transport mechanism and structure-property relationship from this research will provide an important guideline for the future design of organic semiconductors based on donor-acceptor complexes.

Donor-acceptor co-assembled supramolecular nanofibers with high and well-balanced ambipolar charge transport properties under ambient conditions.

Single-bundle nanofiber based OFETs were fabricated from co-assembled supramolecular nanofibers which comprise TCAT and PDI-13, using a simple gelation method. The co-assembled supramolecular nanoarchitecture was fully characterized by means of optical microscopy, TEM, SEM, 2D-GIWAXS and so on. The devices exhibited typical ambipolar charge transport characteristics with very well-balanced hole and electron mobilities as well as high photoresponsivity under ambient conditions.

Single-bundle nanofiber based OFETs fabricated from a cyclic conjugated organogelator with high field-effect mobility and high photoresponsivity.

Single-bundle nanofiber based OFETs were fabricated from a cyclic conjugated organogelator, using a simple gelation method. The devices exhibited typical p-type semiconductor properties with dominant hole transport both in the dark and upon illumination under ambient conditions.

Thiophene-Diketopyrrolopyrrole-Based Quinoidal Small Molecules as Solution-Processable and Air-Stable Organic Semiconductors: Tuning of the Length and Branching Position of the Alkyl Side Chain toward a High-Performance n-Channel Organic Field-Effect Transistor.

A series of thiophene-diketopyrrolopyrrole-based quinoidal small molecules (TDPPQ-2-TDPPQ-5) bearing branched alkyl chains with different side-chain lengths and varied branching positions are synthesized. Field-effect transistor (FET) measurement combined with thin-film characterization is utilized to systematically probe the influence of the side-chain length and branching position on the film microstructure, molecular packing, and, hence, charge-transport property. All of these TDPPQ derivatives show air-stable n-channel transporting behavior in spin-coated FET devices, which exhibit no significant decrease in mobility even after being stored in air for 2 months. Most notably, TDPPQ-3 exhibits an outstanding n-channel semiconducting property with electron mobilities up to 0.72 cm(2) V(-1) s(-1), which is an unprecedented value for spin-coated DPP-based n-type semiconducting small molecules. A balance of high crystallinity, satisfactory thickness uniformity and continuity, and strong intermolecular interaction accounts for the superior charge-transport characteristics of TDPPQ-3 films. Our study demonstrates that tuning the length and branching position of alkyl side chains of semiconducting molecules is a powerful strategy for achieving high FET performance.

Thieno[3,2-b]thiophene-diketopyrrolopyrrole-based quinoidal small molecules: synthesis, characterization, redox behavior, and n-channel organic field-effect transistors.

We report the synthesis, characterization, redox behavior, and n-channel organic field-effect (OFET) characteristics of a new class of thieno[3,2-b]thiophene-diketopyrrolopyrrole-based quinoidal small molecules 3 and 4. Under ambient atmosphere, solution-processed thin-film transistors based on 3 and 4 exhibit maximum electron mobilities up to 0.22 and 0.16 cm(2) V(-1) s(-1) , respectively, with on-off current ratios (Ion /Ioff ) of more than than 10(6) . Cyclic voltammetry analysis showed that this class of quinoidal derivatives exhibited excellent reversible two-stage reduction behavior. This property was further investigated by a stepwise reductive titration of 4, in which sequential reduction to the radical anion and then the dianion were observed.

Charge-transfer complex crystal based on extended-π-conjugated acceptor and sulfur-bridged annulene: charge-transfer interaction and remarkable high ambipolar transport characteristics.

A single crystal of a novel mixed-stack donor-acceptor complex formed by a tetracyanoquinodimethane derivative with an extended π-conjugated system and a sulfur-bridged annulene displays the highest ambipolar transport behavior among donor-acceptor complexes reported with electron and hole mobilities reaching up to 0.24 and 0.77 cm(2) V(-1) s(-1) , respectively.

Supramolecular association behavior of a strong C60 receptor with conjugated pentacene and tetrathiafulvalene moieties in solution and in the solid state.

A π-extended tetrathiafulvalene (exTTF) containing a conjugated pentacene moiety showed a large binding affinity toward C60 in solution. The crystal structure analysis of the cocrystal formed by this exTTF and C60 revealed that strong π-π interactions existed between C60 and naphthalene and 1,3-dithiol-2-ylidene units.

One-pot synthesis of core-expanded naphthalene diimides: enabling N-substituent modulation for diverse n-type organic materials.

A mild and versatile one-pot synthesis of core-expanded naphthalene diimides has been developed, which undergoes a nucleophilic aromatic substitution reaction and then an imidization reaction, allowing an easy and low-cost access to diverse n-type organic materials. Some newly synthesized compounds by this one-pot operation exhibited high electron mobility of up to 0.70 cm(2) V(-1) s(-1) in ambient conditions.