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The photoluminescence (PL) property of two push-pull oligomers named C2B and DC2B, comprising of carbazole and difluoroboron β-diketonate units, were probed by many optical tests. A comparison of the PL property of C2B and DC2B indicated that the introduction of carbazole unit red shifted the spectral feature and accelerated PL relaxation rate. Meanwhile, it also accelerated the rate of intramolecular charge transfer (ICT), the reorganization of excited state and relaxation from the ICT state to the ground state, based on the global analysis of transient absorption data. Finally, C2B and DC2B were mixed together and engineered into white light emitting diode test, showing a correlated color temperatures (CCT) value of 4687 K, indicating their potential in the organic displaying devices. [ABSTRACT FROM AUTHOR]

The photo-physical properties of oligo(fluorene-vinylene) functionalized anthracene linear oligomers (An-OFVn (n=1-4)) have been systemically investigated through experimental and theoretical methods. The steady-state spectral measurement shows that the increasing of fluorene-vinylene (FV) group could lead to the red shift of absorption spectra and restrain the excimer formation between oligomers. Quantum chemical calculations exhibit that the energy levels of HOMO, LUMO, and the band gap gradually converge to a constant in accompany with the increasing of FV unit. Meanwhile, the electronic cloud which distributes on the branch arms, also gradually enhances and makes the absorption spectral shape of oligomers become similar to that of branch arms step by step. The time-resolved fluorescence tests exhibits that the lifetime of excimer emission would be almost invariable after the number of FV group in oligomer is ≥2. In nonlinear optical test, the two-photon photoluminescence efficiency and two-photon absorption cross-section will both gradually enhance and be close to an extremum after the number of FV unit is equal to 4. These results will provide a guideline for the design of novel photo-electronic materials. [ABSTRACT FROM AUTHOR]

We investigate the fluorene-vinylene unit dependent photo-physical properties of multi-branched truxene based oligomers (Tr-OFVn, n=1-4) employing steady-state absorption and emission spectroscopy, transient absorption spectroscopy, two-photon fluorescence, and z-scan technique. The results show that the increasing of fluorene-vinylene unit leads to a red-shift in the spectra of absorption and fluorescence, and shortens the excited state lifetime. Meanwhile, two-photon fluorescence efficiency and two-photon absorption cross section of truxene based oligomers gradually enhance in company with the extension of π-conjugated length. In addition, the values of two-photon absorption cross section modeled on the sum-over-state approach agree well with the experimental ones. The results indicate multi-branched truxene based oligomers bearing oligo(fluorene-vinylene) arms are promising organic materials for two-photon applications. [ABSTRACT FROM AUTHOR]