Study Of Photophysical Properties Of Distyrylbenzene Derivatives

In recent year, the development of organic optoelectronic functional materials has been one of the most exciting and vigorous fields of science research, because of the extremely unique electronic structure and the performance. Along with the vigorous development of the scienc and technology of suparmolecular chemisty, optoelectronic and nanotechnology and so on, the organic optoelectronic functional materials have shown great application potentials in organic light-emitting diodes (OLED), organic field effect transistor (OFET), organic solar cell, organic solid laser, chemical sensors, three-dimensional optical data storage, biological imaging and photodynamic therapy, etc.In the field of organic materials, people have gradually formed a consensus that the properties of solid-state materials closely related to their own molecular structure and aggregation state structure. The understanding of the relationship of molecular structure and properties is most important factor which is achieve the high-performance organic light-emitting materials. The experimental and theoretical researches gradually applied to understanding several classical materials between the molecular aggregation structure and the optoelectrnic properties. There have also formed some methods and ways in designed molecular and the regulative stack structure aspect. This had the important guiding to the material design and the synthesis, but the systematic and thorough understanding of the relations between the structure and the performance of organic luminescent material, and the establishment of luminescence theory system of organic material, still had the massive thorough system work. On?the other hand, organic two-photon absorption materials are being more and more attentions, because they not only have a high optical nonlinear response coefficient and ultra-fast response speed, but also easy to modifity molecular structure and control their optical properties, and very suitable for preparing high-quality optics devices. Thus, the development of two-photon absorption materials with large cross-section, high fluorescence quantum efficiency, and the investigation of the relationship between molecular structure and nonlinear optical properties are one of many common problems in the same field. Therefore, we investigated the relationship of molecule structure and performance of distyrylbenzene derivatives.The crystal structures and photophysical properties of three 9,10- distyrylanthracene (DSA) derivatives were investigated. Their crystal structures exhibit nonplanar conformations due to the supramolecular interactions resulting in rigid molecules and relative tight stacking. The three DSA derivatives (DSA, BMSA and BMOSA) possess a typical aggregation-induced emission (AIE) property, i.e., they exhibit faint emission in their solutions but intense emission in their crystals as a result of the dominant nonradiative decay by free intramolecular torsion in the solution and the restricted torsional motion by supramolecular interaction in the crystal. The investigation of the relationship between the crystal structures and AIE properties of the four DSA derivatives indicates that DSA moiety is the key factor of AIE property because of the restricted intramolecular torsion between the 9,10-anthrylene core and the vinylene moiety. The ASE from the high-quality large single crystal of BMSA with high photoluminescence efficiency was observed. The FWHM of the narrowed spectra can reach 10 nm and the threshold of ASE is about 10μJ/pulse. The observation of ASE with low threshold value indicates that the BMSA crystals are good candidates for the organic solid state laser.An unusual luminescence properties of ?-conjugated dendrimers An-G0, An-G1 and An-G2, in which 9,10-anthrylene was served as the core and triphenylamine connected by alkene as the branching moieties. The synthetic strategy for the preparation of triphenylamine-based dendrons developed through a facile convergent iterative procedure without any protection-deprotection chemistry. These dendrimers have shown an unusual fluorescence behavior, that is, weak fluorescence in a dilute solution, but enhanced fluorescence in nanoaggregated dispersions or solid state. The theoretical and experimental evidences demonstrated the enhanced fluorescence owing to the restricted motions of intramolecular torsional core. These dendrimers showed excellent solid-state luminescence efficiency, 32.6% for An-G2, which are promising good candidates as emissive materials for optoelectronic devices.The linear photophysical properties, two-photon absorption (TPA), and optical limiting behavior of three ?-conjugated dendrimers (Ph-G0, Ph-G1 and Ph-G2) were investigated in solution at room temperature. Linear absorption and emission spectra revealed a bathochromic shift and decreased fluorescence quantum yields with increasing dendrimer generation. A strong cooperative effect in the TPA absorption of these dendrimers was observed. The TPA cross-sections increase gradually with the proportion of triphenylamine units and the maximum value of the TPA cross-section can reach 5690 GM for Ph-G2. These triphenylamine-based dendrimers exhibited efficient two-photon optical limiting under femtosecond excitation. Two-photon induced amplified spontaneous emission (ASE) characteristics of a needle like crystal of Ph-G0 were studied. The FWHM of the two-photon excited fluorescence can reach 6.5nm and ASE threshold reached 0.29 mJ·pulse-1·cm-2 for the crystal pumped with femtosecond laser. Under two-photon excitation, the up-converted light emission was confined within the crystal and self-waveguided along the needle axis then radiated from the tips of the needles. The needlelike crystal of Ph-G0 is shown to be a promising candidate for frequency up-converted organic semiconductor laser.