Zitong Liu

New Organic Semiconductors with Imide/Amide‐Containing Molecular Systems

Due to their high electron affinities, chemical and thermal stabilities, π-conjugated molecules with imide/amide frameworks have received considerable attentions as promising candidates for high-performance optoelectronic materials, particularly for organic semiconductors with high carrier mobilities. The purpose of this Research News is to give an overview of recent advances in development of high performance imide/amide based organic semiconductors for field-effect transistors. It covers naphthalene diimide-, perylene diimide- and amide-based conjugated molecules and polymers for organic semiconductors.

Significant Improvement of Semiconducting Performance of the Diketopyrrolopyrrole–Quaterthiophene Conjugated Polymer through Side-Chain Engineering via Hydrogen-Bonding

Three diketopyrrolopyrrole (DPP)-quaterthiophene conjugated polymers, pDPP4T-1, pDPP4T-2, and pDPP4T-3, in which the molar ratios of the urea-containing alkyl chains vs branching alkyl chains are 1:30, 1:20, and 1:10, respectively, were prepared and investigated. In comparison with pDPP4T without urea groups in the alkyl side chains and pDPP4T-A, pDPP4T-B, and pDPP4T-C containing both linear and branched alkyl chains, thin films of pDPP4T-1, pDPP4T-2, and pDPP4T-3 exhibit higher hole mobilities; thin-film mobility increases in the order pDPP4T-1 < pDPP4T-2 < pDPP4T-3, and hole mobility of a thin film of pDPP4T-3 can reach 13.1 cm(2) V(-1) s(-1) after thermal annealing at just 100 °C. The incorporation of urea groups in the alkyl side chains also has an interesting effect on the photovoltaic performances of DPP-quaterthiophene conjugated polymers after blending with PC71BM. Blended thin films of pDPP4T-1:PC71BM, pDPP4T-2:PC71BM, and pDPP4T-3:PC71BM exhibit higher power conversion efficiencies (PCEs) than pDPP4T:PC71BM, pDPP4T-A:PC71BM, pDPP4T-B:PC71BM, and pDPP4T-C:PC71BM. The PCE of pDPP4T-1:PC71BM reaches 6.8%. Thin films of pDPP4T-1, pDPP4T-2, and pDPP4T-3 and corresponding thin films with PC71BM were characterized with AFM, GIXRD, and STEM. The results reveal that the lamellar packing order of the alkyl chains is obviously enhanced for thin films of pDPP4T-1, pDPP4T-2, and pDPP4T-3; after thermal annealing, slight inter-chain π-π stacking emerges for pDPP4T-2 and pDPP4T-3. Blends of pDPP4T-1, pDPP4T-2, and pDPP4T-3 with PC71BM show a more pronounced micro-phase separation. These observations suggest that the presence of urea groups may further facilitate the assemblies of these conjugated polymers into nanofibers and ordered aggregation of PC71BM.

Peripherally dimethyl isophthalate-functionalized poly(benzyl ether) dendrons: a new kind of unprecedented highly efficient organogelators.

A series of poly(benzyl ether) dendrons, up to the fourth generation, decorated in their periphery with dimethyl esters were divergently synthesized and fully characterized. These dendrons were found to be unprecedented highly efficient organogelators toward various aromatic and polar organic solvents with the critical gelator concentration (CGC) approaching 2.2 mg/mL. The gelation ability was found to be highly dependent on the nature of the peripheral groups, dendron generation, and the dendritic architecture. The large monodisperse dendron G(4) with a globular shape could also form stable gels in several aromatic solvents with relatively high CGCs. A number of experiments (SEM, TEM and AFM imaging, X-ray crystal structure analysis, concentration- and temperature-dependent (1)H NMR spectroscopy, fluorescence spectroscopy, and powder X-ray diffraction) confirmed the self-aggregation of these dendrons, despite the lack of any conventional gelating motifs such as amides, long alkyl side chains, and steroidal groups. The multiple strong pi-pi stacking interactions due to the peripheral dimethyl isophthalate rings and the internal benzyl rings are found to be the key contributor in forming the self-assembled gel.

Butanol production from corncob residue using Clostridium beijerinckii NCIMB 8052

Aims:  To determine whether corncob residue (CCR) could be a good substrate for butanol production.

A facile and convenient fluorescence detection of gamma-ray radiation based on the aggregation-induced emission

A facile and convenient fluorescence detection of gamma-ray radiation is reported. This is based on the ensemble of silole 1 and polymer 2, by taking advantages of AIE (aggregation-induced emission) behavior of silole compounds and the fact that polymers with –SO2groups in the main chain can be degraded upon gamma-ray radiation. The fluorescence intensity of the ensemble of silole 1 and polymer 2 decreases gradually after exposure to increasing dose of gamma-ray radiation. The detection of gamma-ray radiation with silole 1 and polymer 2 can be performed at ambient conditions and gamma-ray radiation as low as 0.13 kGy dose can be successfully detected.

Dithiazole-fused naphthalene diimides toward new n-type semiconductors

A simple synthetic approach to dithiazole-fused naphthalene diimides 1 and 2 from 2,6-dibromoNDI (2BrNDI) was described. Note that the synthesis did not involve any metallic catalysts. Based on their cyclic voltammograms, the LUMO energies of 1 and 2 were estimated to be −3.99 eV and −3.98 eV, respectively, being lower than that of unsubstituted NDI. Thin films of 1 and 2 show n-type semiconducting behaviors. OFETs of 1 exhibit electron mobility up to 0.15 cm2 V−1 s−1 with high on/off ratio (under ambient conditions) after annealing.

Solution-processed core-extended naphthalene diimides toward organic n-type and ambipolar semiconductors

In this paper, we report four new core-extended NDI molecules 1, 2, 3 and 4. 1 and 2 entail two benzene rings and two naphthalene rings, respectively; 3 and 4 contain benzene and naphthalene rings as well as 2-(1,3-dithiol-2-ylidene)malonitrile groups. All of them can be easily synthesized with acceptable yields. HOMO/LUMO energies of 1, 2, 3 and 4 were −5.66 eV/−3.93 eV, −5.73 eV/−3.91 eV, −5.88 eV/−4.22 eV and −5.89 eV/−4.23 eV, respectively. OFETs with thin-films of 1, 2, 3 and 4 were successfully fabricated with conventional techniques. Thin-films of 1 and 2 exhibit ambipolar semiconducting properties under N2 atmosphere with relatively balanced hole and electron mobilities, which can further increase after annealing; hole and electron mobilities reach 0.047 and 0.016 cm2 V−1 s−1, respectively for the thin-film of 2 after annealing at 140 °C. Moreover, two identical ambipolar transistors with thin films of 2 were combined into an inverter circuit with a gain of 11. 3 and 4 behave as n-type semiconductors in air, and the electron mobility can reach 0.22 cm2 V−1 s−1 for the thin-film of 3 with an Ion/off of 106 after annealing at 120 °C. XRD and AFM studies are also presented for understanding the variation of carrier mobilities of thin-films of 1, 2, 3 and 4 after annealing at different temperatures.

New π-conjugated polymers as acceptors designed for all polymer solar cells based on imide/amide-derivatives

In this paper we report two n-type polymeric acceptors P1 and P2 based on imide/amide-derivatives (PDI, NDI and DPP). P1 and P2 exhibit very different optical properties which may be related to the different molecular configuration and polymeric crystallinity. All polymer solar cells were fabricated with conventional configuration based on polymeric donor PBDTTT-C-T and P1/P2. Results reveal that devices based on P1 show the best performance with a PCE of 2.01%, a V-OC of 0.68 V, a J(SC) of 7.06 mA cm 2 and a FF of 41.78%, which is attributed to the appropriate energy levels, relatively high electron mobility and preferable micro-phase separation. The poor performance for P2 ( PCE = 0.30%) was mainly ascribed to its extremely low J(SC) which was probably caused by the small HOMO energy level difference between donor and P2.

New dithienyl-diketopyrrolopyrrole-based conjugated molecules entailing electron withdrawing moieties for organic ambipolar semiconductors and photovoltaic materials

In this paper we report two DPP-based conjugated molecules DPPBT and DPPTT in which the respective electron withdrawing moieties 2,1,3-benzothiadiazole and thiazolo[5,4-d]thiazole are flanked by two DPP moieties. For comparison, DPPBZ containing 1,4-diethynylbenzene and two DPP moieties were synthesized. HOMO/LUMO energies of DPPBT, DPPTT and DPPBZ were estimated on the basis of cyclic voltammetric data. Owing to the fact that LUMO energies of DPPBT and DPPTT were lowered to ca. −3.5 eV, thin films of both DPPBT and DPPTT exhibit ambipolar semiconducting properties under N2 atmosphere with hole and electron mobilities up to 0.25 cm2 V−1 s−1 and 0.09 cm2 V−1 s−1, respectively. In comparison, thin film of DPPBZ just shows p-type semiconducting property. Notably, ambipolar semiconductors with relatively high carrier mobility are rarely reported for DPP-containing small conjugated molecules. Alternatively, both DPPBT and DPPTT can function as electron donors for photovoltaic materials. Thin films of DPPTT:PC71BM and DPPBT:PC71BM at a weight ratio of 1 : 1 exhibit PCEs of 4.18% and 2.44%, respectively, with VOC higher than 0.95 V.

Fluorescent polymeric micelles with tetraphenylethylene moieties and their application for the selective detection of glucose.

By linking TPE moieties that exhibit aggregation-induced (enhanced) emission to the amphiphilic copolymer 1, fluorescent micelles are prepared and characterized. The polymeric micelles exhibit relatively strong fluorescence which can be tuned by heating and cooling. By combining cascaded enzymatic (oxidation of D-glucose with GOx) and chemical (oxidation of I(-) by H(2) O(2) ) reactions, the fluorescent micelles of copolymer 1 are successfully utilized for the selective detection of D-glucose in aqueous solution. The influences of proteins (e.g., bovine serum albumin) and reductants (e.g., ascorbic acid) on this fluorescence detection of D-glucose are also discussed.