| Two-photon absorption materials have shown great potential applications in high-density data storage, single-molecule detection, medical diagnosis, three-dimensional microfabrication and many other fields due to the unique optical response,nonlinear properties,3D processing capabilities and high spatial resolution. Therefore,to get the materials with large two-photon absorption cross section as well as strong two-photon fluorescence has become one of the most attractive topics in photoluminescence, electroluminescence, thin film transistor, chemical sensor, photovoltaic cell, and nonlinear optics .The synthesis and large two-photon absorption (TPA) properties of three novel solid red-emitting 2,5-dioctyl-1,4-diketo-3,6-diphenyl-pyrrolo[3,4-c]pyrrole (DPP) /3,6-carbazole (Cz)/terfluorene (TF) alternating copolymers with the molar ratios of DPP vs. TF (15:85 (TCP15), 25:75 (TCP25), and 50:50 (TCP50))are reported. These copolymers possess donor–π-bridge–acceptor–π-bridge–donor (Cz-DPP-Cz) and donor–π-bridge–donor (Cz-TF-Cz) motifs, which can enhance intramolecular charge transfer to endow the copolymers with large TPA cross sections (δ) and red-shifted emission. In dilute solutions, all three copolymers exhibit two distinguished one-photon absorption and emission bands, implying that the electronic states of the two components (Cz-DPP-Cz and Cz-TF-Cz) in alternating copolymers are not well mixed and the energy transfer from TF segments to DPP units is incomplete. However, in thin film states, all three copolymers are monochromatic red-emitting with the peaks at 617, 621, 631 nm for TCP15, TCP25, and TCP50, respectively, indicating that the energy transfer from TF segments to DPP units is complete and that the interchain interactions have also played an important role in the energy transfer. Two-photon properties are measured in THF by using two-photon-induced fluorescence method under femtosecond laser pulses. The copolymer solutions still exhibit two distinguished emission bands but the short-wavelength emissions are obviously decreased in comparison with one-photon excitation, which implies that Cz-TF-Cz segments is high one-photon active but low TPA active, Cz-DPP-Cz units are low one-photon active but high TPA active. Theδvalues of the copolymers increase with DPP contents and are up to 530, 770 and 850 GM per repeating unit for TCP15, TCP25 and TCP50, respectively. Moreover, all the copolymers show largeδover the range of measured wavelengths.In order to study the effects on photo-physical properties of the anthracene derivatives brought by the conjugate structures, we have synthesized 9,10-bis(3,5- dimethyl phenyl) anthracene (DPA), 9- p-tert-butyl phenyl-10-phenylethenyl anthracene (PSA) and 9,10-bis(4- tert-butyl- phenylethenyl) anthracene (DSA). We have found that the photo-physical properties of PSA are between DPA and DSA. Most organic light-emitting materials have very good luminous property in solution condition, but the luminous properties are bad in aggregative states. However, DSA has AIE (Aggregation Induced Emission) effect. This discovery provides theoretical basis for the further research in this field. |
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