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The growth of covalent organic frameworks (COFs) normally goes through a fast polymerization process, which quickly forms amorphous powder and then slowly crystallizes to obtain nanometer-sized cry...

Near-infrared organic photodetectors (NIR OPDs) own some unique properties such as tailorable optoelectronic properties, ease of processing, compatibility with flexible substrates, and operation at...

Two new diketopyrrolopyrrole-based π-conjugated copolymers (PDPP6T and PDPP7T) have been synthesized by Stille coupling polymerization of 3,6-bis(5′-bromo-[2,2′-bithiophen]-5-yl)-2,5-bis(2-octyldodecyl)pyrrolo-[3,4-c]pyrrole-1,4(2H,5H)-dione with α,α′-bis(trimethylstannyl)-bithiophene and α,α′-bis(trimethylstannyl)-terthiophene, respectively. The impressive high mobility of 3.94 cm2 V–1 s–1 for the polymer with sextetthiophene (6T) and of 2.82 cm2 V–1s–1 for polymer with septetthiophene (7T) is acquired. It is found that the introduction of longer β-unsubstituted oliogothiophene unit in DPP-based copolymers has a great influence on the molecular weight and solubility of the DPP-oligothiophene copolymers that finally affects the organic thin-film transistor (OTFT) performances, indicating that a suitable number of thiophene group in β-unsubstituted oligothiophene exists for such a kind of copolymer to exhibit the best OTFT performances. This work also reveals the significance in the design of D–A copolymer...

We report the synthesis of two novel donor–acceptor copolymers poly{[N, N′-bis(alkyl)-1,4,5,8-naphthalene diimide-2,6-diyl-alt-5,5′-di(thiophen-2-yl)-2,2′-(E)-2-(2-(thiophen-2-yl)vinyl)thiophene]} (PNVTs) based on naphthalenediimide (NDI) acceptor and (E)-2-(2-(thiophen-2-yl)vinyl)thiophene donor. The incorporations of vinyl linkages into polymer backbones maintain the energy levels of the lowest unoccupied molecular orbits at −3.90 eV, therefore facilitating the electron injection. Moreover, the energy levels of the highest occupied molecular orbits increase from −5.82 to −5.61 eV, successfully decreasing the hole injection barrier. Atomic force microscopy measurements indicate that PNVTs thin films exhibit larger polycrystalline grains compared with that of poly{[N, N′-bis(2-octyldodecyl)-1,4,5,8-naphthalene diimide-2,6-diyl]-alt- 5,5′-(2,2′-bithiophene)} [P(NDI2OD-T2)], consistent with the stronger π–π stacking measured by grazing incidence X-ray scatting. To optimize devices performance, field-effect ...

In this paper, we report the synthesis and characterization of two new D-A-D molecules (E)-5,5′-bis(5-(benzo[b]thiophen-2-yl)thiophen-2-yl)-1,1′-bis(2-ethyl- hexyl)-[3,3′-bipyrrolylidene]-2,2′(1H,1′H)-dione (BTBPD) and (E)-5,5′-bis- (5-(benzo[b]furan-2-yl)thiophen-2-yl)-1,1′-bis(2-ethylhexyl)-[3,3′-bipyrrolylidene]-2,2′(1H,1′H)-dione (BFBPD). They entail bipyrrolylidene-2,2′(1H,1′H)-dione (BPD, known as Pechmann dye) as the electron-accepting core that is flanked by two benzo[b]thiophene moieties and two benzo[b]furan moieties, respectively. Crystal structures of BTBPD and BFBPD provide solid evidence for the intermolecular donor–acceptor (D-A) interactions, which are favorable for improving charge transport performance. Organic field-effect transistors (OFETs) were prepared based on thin films of BTBPD and BFBPD through solution-processed technique. OFETs of BTBPD exhibit relatively high hole mobility up to 1.4 cm2 V–1 s–1 with high on/off ratio up to 106. In comparison, the hole mobility of OFETs with B...

A new diketopyrrolopyrrole-based π-conjugated copolymer (PDPP5T) with high molecular weight has been synthesized by Stille coupling polymerization of 3,6-bis(5-bromothiophen-2-yl)-2,5-bis(2-octyldodecyl)pyrrolo-[3,4-c]pyrrole-1,4(2H,5H)-dione with α,α′-bis(trimethylstannyl)-terthiophene. Its hole mobility without thermal annealing reaches 1.08 cm2 V–1 s–1, and a higher hole mobility of 3.46 cm2 V–1 s–1 is obtained annealed at 200 °C directly in an air atmosphere. This indicates that introducing a longer β-unsubstituted quinquethiophene (5T) unit into the main-chain of DPP-oligothiophene copolymer produces much pronounced p-type behavior and also reduces the steric hindrance of the bulk side-chain groups, which is favorable to enhance the molecular ordering capability at low temperatures and improve the organic thin-film transistors (OTFT) performances. This work demonstrates that PDPP5T is a promising material that can be applied to the cost-effective and large-scale production of OTFTs.

Four families of core-expanded naphthalene diimide (NDI) derivatives were designed and synthesized, namely, NDI-DTYM2 (1−7, of which 1 and 2 were previously reported), NDI-DTDCN2 (8 and 9), NDI-DTYCA2 (10 and 11), and NDI-DCT2 (12), where the NDI core fuses two 2-(1,3-dithiol-2-ylidene)malonitrile (DTYM) groups, two 1,4-dithiine-2,3-dicarbonitrile (DTDCN) groups, two alkyl 2-(1,3-dithiol-2-ylidene)cyanoacetate (DTYCA) groups, and two 2,3-dicyanothiophenes (DCT), respectively. The NDI cores of the present compounds bear the branched N-alkyl substituents with the carbon atom numbers from 12 to 24, which guarantees good material solubility. The solution-processed, bottom-gate organic thin film transistors based on new compounds 3−12 operate well in air with the electron mobility ranging from ∼10−6 to 0.26 cm2 V−1 s−1, depending on the nature of the branched N-alkyl substituent and the π-backbone structure.

One-dimensional (1D) nanostructures of the wide band gap semiconductors are promising building blocks for photoelectric nanodevices. However, some problems like strong 1D confinement largely hamper their applications. To avoid these problems, here, we provide another 1D configuration, in which an inner-wire coaxial Schottky junction exists, thus effectively avoiding the recombination of the photoexcited carriers. As an example, we produce ZnS/carbon nanotube nanocables with uniform morphologies by a two-step vapor deposition method and find that they have good conductance, obvious light response, and ohmic contacts with electrodes, avoiding the limitations of both the pristine nanomaterials. We believe that this configuration would be valuable for applying the 1D nanomaterials in photoelectronics.

The patterning of an organic layer, a big challenge for organic field-effect transistors (OFETs), have recently received considerable attention. By using copper tetracyanoquinodimethane (Cu-TCNQ) modified copper electrodes with nanostructure, selective polycrystalline growth of organic semiconductors is achieved. For different organic semiconductors, varied ways for crystal growth are observed. The OFETs based on selectively deposited tetracyanoquinodimethane (TCNQ), rubrene, and copper phthalocyanine crystals are fabricated and exhibit good device performance. Rubrene devices exhibit maximum field-effect mobility up to 4.6 cm2/(V·s) which is comparable to that of corresponding single crystal device. In addition, an organic inverter made of patterned rubrene and TCNQ exhibits a gain of 23. These results offer a general approach to the fabrication of high performance OFETs and organic circuits.

Two novel wide-energy-gap molecules, 1,3-bis(9-phenyl-9H-fluoren-9-yl)benzene (mDPFB) and 1,4-bis(9-phenyl-9H-fluoren-9-yl)benzene (pDPFB), suitable for blue phosphorescent host materials, were designed and prepared. The thermal, photophysical, and electrochemical properties as well as electroluminescence characteristics were fully investigated. Both mDPFB and pDPFB possess high singlet (4.0 eV) and triplet (2.8 eV) energies, well energy-matched with the deep-blue phosphorescent dopant, iridium(III) bis(4′,6′-difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate (FIr6). The single crystals of the newly synthesized compounds mDPFB and pDPFB were grown, and their crystal structures were determined by X-ray diffraction. Both molecules adopt a rigid twisted tetrahedral crystallographic conformation, and no facial to facial π−π stacking exists in the solid state. The substituents at the 1,4-positions of benzene enhance the twisted degree of the fluorenyl rings and have predominant influence on the thermal and m...

Zinc(II)-2-(2-hydroxyphenyl)benzothiazolate complex is an excellent white-light-emitting material. Despite some studies devoted to this complex, no information on the real origin of the unusually broad electroluminescent (EL) emission is available. Therefore, we investigate photoluminescent and EL properties of the zinc complex. Orange phosphorescent emission at 580 nm was observed for the complex in thin film at 77 K, whereas only fluorescent emission was obtained at room temperature. Molecular orbitals, excitation energy, and emission energy of the complex were investigated using quantum chemical calculations. We fabricated the device with a structure of ITO/F16CuPc(5.5 nm)/Zn-complex/Al, where F16CuPc is hexadecafluoro copper phthalocyanine. The EL spectra varied strongly with the thickness of the emissive layer. We observed a significant change in the emission spectra with the viewing angles. Optical interference effects and light emission originating both from fluorescence and from phosphorescence ca...

The novel perylene bisimides functionalized with oligothiophene substituents in the bay position of the perylene core N,N‘-di(2-ethylhexyl)-1,7-di(thiophen-2-yl)perylene-3,4,9,10-tetracarboxylic acid bisimide (2a), N,N‘-di(2-ethylhexyl)-1,7-di[(2,2‘)bithiophen-5-yl]perylene-3,4,9,10-tetracarboxylic acid bisimide (2b), and N,N‘-di(2-ethylhexyl)-1,7-di[(2,2‘;5‘,2‘ ‘)terthiophen-5-yl]perylene-3,4,9,10-tetracarboxylic acid bisimide (2c) have been synthesized and fully characterized. As compared to the unsubstituted perylene bisimide (3), the UV−vis absorptions of 2a−c undergo a bathochromic shift along with considerable band broadening and a less pronounced vibronic fine structure. Moreover, efficient intramolecular electron transfer between the oligothiophene-donor and perylene-acceptor leads to remarkable fluorescence quenching of the perylene core. Cyclic voltammetry measurements of these compounds were performed and corresponding polymers from the monomers 2b and 2c were prepared by electrochemical polyme...

A novel series of conjugated copolymers having fluorene and binaphthyl moieties in the main chain and based on cyanostilbene were synthesized in good yields by a palladium-catalyzed Suzuki coupling reaction, a new approach different from the traditional Knoevenagel condensation polymerization. Through controllable modification of the main chain structures, not only were the thermal, electronic, and optical properties of the polymers tuned, but also the structure−property relationships were studied. All these polymers possess excellent thermal stability with glass-transition temperatures of 60−159 °C and onset decomposition temperatures of 411−417 °C. Cyclic voltammetry studies reveal that these copolymers have low-lying LUMO energy levels ranging from −2.92 to −3.08 eV and low-lying HOMO energy levels ranging from −6.01 to −6.13 eV, and they may be promising candidates for electron-transporting or hole-blocking materials in light-emitting diodes (LEDs). The polymers in thin films emit strong blue luminanc...

A novel donor−acceptor conjugated copolymer consisting of the electron-accepting moiety 2,7-diethynylfluorene and the electron-donating moiety tetraphenyldiaminobiphenyl (TPD), i.e., poly{(2,7-diethynyl-9,9-di-2-ethylhexylfluorene)-alt-co-[N,N‘-diphenyl-N,N‘-bis(4-phenyl)-1,1‘-biphenyl-4,4‘-diamine]} (TPD-PFE), and its cousins without the alkyne or TPD segments, namely, poly{(9,9-di-2-ethylhexyl-2,7-fluorene)-alt-co-[N,N‘-diphenyl-N,N‘-bis(4-phenyl)-1,1‘-biphenyl-4,4‘-diamine]} (TPD-PF) and poly(2,7-9,9-di-2-ethylhexylfluorenyleneethynylene) (PFE), were synthesized via Pd-catalyzed coupling reactions. The third-order nonlinear optical (NLO) properties of these polymers were characterized using a femtosecond time-resolved optical Kerr effect technique. The ultrafast second-order hyperpolarizability of TPD-PFE was estimated to be as large as 4.5 × 10-30 esu in the nonresonant region, larger than those of its counterparts. The electronic transitions of the fluorene-based polymers can be readily tuned by vary...

New luminescent polymers that contain both electron-withdrawing cyano groups and electron-rich moieties, triphenylamine (TPA) or tetraphenyldiaminobiphenyl (TPD), were synthesized by Knoevenagel condensation of 1,4-bis(cyanomethyl)-2-[(2-ethylhexyl)oxy]-5-methoxybenzene with the dialdehyde of TPA or TPD, respectively. The polymers were characterized by NMR, FT-IR, microanalysis, GPC, DSC, and TGA. Efficient orange photoluminescence was observed with an absolute quantum efficiency of 48% for the TPA incorporated polymer (TPA-CNPPV). Cyclic voltammetry investigation showed that the polymers presented reversible oxidation and reduction with relatively low potentials, which suggested that the polymers have both good electron and hole injection abilities. We demonstrated an effective approach to synthesize polymers with the triad properties of efficient photoluminescence, good hole injection and high electron-affinity properties, which are highly desirable for application in light-emitting devices. This point ...

An asymmetric heteroacene compound anthra[2,3-b]benzo[d]thiophene has been facilely synthesized. FETs fabricated with the compound exhibit a mobility as high as 0.41 cm2 V−1 s−1 at room temperature. High mobility and good stability suggest that exploration of asymmetric organic semiconductors would be extremely promising for the application in organic electronics.

A new electroluminescent copolymer incorporating both a highly efficient hole-transporting moiety, tetraphenyldiaminobiphenyl (TPD), and a light-emitting moiety, 2-(2‘-ethylhexyloxy)-5-methoxy-1,4-...

Novel regioregular polythiophene derivatives with conjugated bridges as linking chains, PT-VTVTV2 and PT-VTVTV4, can be used as the semiconductors in organic field-effect transistors (OFETs) and show excellent FET characteristics with a field-effect mobility of 3.8 × 10-3 cm2 V-1 s-1 and a current on/off ratio of 104.

A series of CuTCNQ (TCNQ = 7,7,8,8-tetracyano-p-quinodimethane) thin-film materials were prepared by different methods or under different conditions and characterized by scanning electron microscopic analyses, infrared, Raman, and UV−vis spectral analyses, and current−voltage characteristic measurements. All of the spectral analyses were compared with those of chemically synthesized pure CuTCNQ powder produced by the metathetical reaction of CuI and TCNQ. The effects of the preparation methods or growth parameters upon the morphology of the film materials and their physical properties were discussed.

The rare-earth coordination compound (E)-N-hexadecyl-4-(2-(4-(dimethylamino)phenyl)-ethenyl)pyridinium tetrakis(1-phenyl-3-methyl-4-benzoyl-5-pyrazolonato)dysprosium(III) was synthesized. The LB films were prepared and characterized by UV-vis, IR, X-ray photoelectron spectroscopy, and low-angle X-ray diffraction. High-quality LB films up to 50 layers on the hydrophilic substrates of quartz, calcium fluoride, and glass were obtained. From the second-harmonic generation measurement, second-order molecular hyperpolarizability {beta} of the dysprosium complex was estimated to be about (6.6-9.3) x 10{sup {minus}28} esu. 14 refs., 6 figs., 1 tab.

A conjugated light-emitting polymer based on the binaphthyl structure was synthesized via the Wittig−Horner condensation reaction. By introducing a twisted, noncoplanar binaphthyl unit, it provides an effective approach for tailoring the spectral characteristics and solubility of the polymer. The polymer has a very high glass transition temperature (Tg) of 225 °C and good solubility in common organic solvents. A single layer light-emitting diode with a configuration of (ITO/polymer/Al) showed a respectable external quantum efficiency of 0.1%.