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We have synthesized and characterized a polyfluorene derivative composed of octyl-substituted thieno[3,2,-b]thiophene and 2,1,3-benzothiadiazole as an acceptor unit. The best power conversion efficiencies of the polymer were showed with 1.63% and 2.31% by using PCBM and PC71BM, respectively.

In this paper, we report synthesis and characterization of alkylated fullerene derivatives for solution-processable organic thin film transistors and solar cells. Their physical, thermal, and semiconducting properties have been studied. Organic thin-film transistors fabricated from C60TH-Oc exhibit electron mobilities as high as 3.2 x 10(-2) cm2 V(-1) s(-1) with 32 V of a threshold voltage. The best power conversion efficiency (PCE) was observed in a layered structure P3HT:C60TH-Oc (PCE = 0.44%), which was a twice value of P3HT:C60TH-Dd (PCE = 0.23%).

Here we report on the synthesis and characterization of anthracene derivative for solution processable organic field-effect transistors. The transistor devices with bottom-contact geometry provided a maximum field-effect mobility of 3.74 x 10(-4) cm2 V(-1) s(-1) as well as current on/off ratio of 5.05 x 10(4) and low threshold voltage. Structural information in the solid state is obtained by thermal analysis and two-dimensional wide angle X-ray scattering (2D-WAXS). From the 2D-WAXS, it is clear that the planes of anthracene rings and benzene ring of the molecule are different in solid state. We assume similar arrangement in the thin-film which limit the effective hopping and thus charge mobility.

New spirofluorene-based quadrupolar two-photon absorbing dyes having triphenylamine and N,N-dibutylaniline as electron donors at the end of molcules were designed and synthesized. The third-order nonlinear optical properties of these compounds were studied using a two-photon excited fluorescence method. They were found to have high two-photon absorption cross-section owing to extended conjugation of the spirofluorene moiety. The effect of varying the donor strength could be discerned by comparing the two compounds. They were successfully used as a photosensitizers for two-photon initiated polymerization of three-dimensional micro-objects.

Crosslinkable NLO dendrimers based on azobenzene-type chromophores were synthesized by a Diels-Alder reaction. Their thermal and optical properties were investigated before and after poling at a high temperature. We found that the dendrimers retained good thermal stability up to 260 degrees C after curing at 130 degrees C for 10 min based on thermal analysis. Through in-situ poling and curing processes, the highest NLO activity of the dendrimers was d33 = 1.7 x 10(-6) esu at 1064 nm, which was determined by a Maker fringe experiment.

A near-field scanning microwave microscope (NSMM) is used to detect sequence-specific hybridization between surface-immobilized and free DNA single strands. Hybridization between target (free) and capture (immobilized) sequences leads to changes in the reflection coefficient (S11) which are measured by the NSMM. These changes are caused by hybridization-induced modification of the dielectric constant profile of the DNA film. NSMM instrumentation does not require labeling of target sequences with fluorophores or other tagging groups. The physical basis of reflection coefficient changes underpinning the NSMM approach is discussed.

A soluble truxene derivative (TR1) attached with triphenylamine at the peripheral position was designed and synthesized. The structure and purity of TR1 were carefully characterized by 1H NMR, UV/vis and photoluminescent spectroscopy, mass spectroscopy, and thermal analyses. It exhibited good solubility in common organic solvents and good film forming properties. The maximum absorption and emission peaks in THF solution were shown at 358 nm and 415 nm, respectively. Bright blue emission was observed in both solution and solid states under UV excitation. The fluorescent quantum efficiency was 0.46. The best luminous efficiency was found to be 3.65 cd/A with CIE coordinates of (0.163, 0.260) in electroluminescence devices.

We report here the synthesis and characterization of novel diethynylbenzene-based liquid crystalline semiconductor (P1) for organic thin-film transistors (OTFTs). Compound P1 was synthesized by the Sonogashira coupling reaction between 2-bromo-5-(4-hexylthiophen-2-yl)thieno[3,2-b]thiophene and 1,4-bis(dodecyloxy)-2,5-diethynylbenzene. Top contact OTFTs were fabricated by spin casting with 2 wt% solution of P1 in chloroform and their best performance, which exhibited a hole mobility of 4.5 x 10(-5) cm2/Vs, was showed after annealing of the films at liquid crystalline temperature. Time-of-flight (TOF) mobility measured at liquid crystalline phase was observed to be 1.5 x 10(-6) cm2/Vs for both positive and negative carriers. These results indicate that the liquid crystallinity helps to improve the molecular packing and enhance charge mobility for P1. These advantages can be applicable to design and construct solution-processable OTFT materials for electronic applications.

Two- and three-photon absorption properties of the fluorene-based chromophores have been investigated. The two- and three-photon absorption cross-section are found to be increased with the strength of the electron donor groups in the order of N-ethylcarbazoyl (1), triphenylamino (2), and N,N-dibutylanilino (3) groups. This nonlinear absorption enhancement can be interpreted by the increase of intramolecular charge transfer facilitated by strong electron donors and the decreased detuning energy (deltaE). Furthermore, direct laser microfabrication by two-photon photopolymerization with compound 2 as a two-photon sensitizer was carried out. Laser exposure time-dependent lateral voxel size has also been studied.

A novel method for the fabrication of polypyrrole nanotubes (PPyNTs) possessing quantum dots (QDs) was developed for optoelectronic devices. PbSe QDs were effectively attached to the thiolated PPyNT-SH without affecting the dispersion stability of QDs and hence ensuring their homogeneous distribution in the polymer. Transmission electron microscopic images showed a large number of PbSe QDs absorbed in PPyNT-SH. The polymer nanotube composites were also investigated for the application of photovoltaic cells. An open circuit voltage (V(oc)) of 0.45 V and short-circuit photocurrent density (I(sc)) of 2.4 microA cm(-2) were found in P3HT/PPyNT-PbSe polymeric solar cells. Further optimization will be provided by changing various parameters and conditions.