A germafluorene-fluorene copolymer was successfully obtained via Suzuki polymerization. The germanium containing copolymer has an efficient blue light emission under the ultraviolet irradiation and its single layer EL device showed the highest brightness of 2630 cd/m 2 at 7.8 V and the highest efficiency of 0.301 lm/W at 6.2 V. The copolymer can also serve as the host material for phosphorescent metal complexes with the maximum brightness of 15600 cd/m 2 and the quantum efficiency of 8.5%. The results are quite promising and promise that as its analogs of fluorene and silafluorene, germafluorene is an excellent building block for blue light-emitting polymers and host materials.

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Vinylsilafluorene (VSiF) was successfully synthesized and copolymerized with vinylcarbazole and methyl methacrylate via free radical copolymerization for the first time. The synthesis, photophysical properties, computational modeling studies, and organic light-emitting devices of the VSiF copolymers were presented. The good coordinated photoluminescent (PL) spectra with the absorption of blue light-emitting materials and the high energy band-gap of the VSiF copolymers were observed. Higher triplet band gap ( 3 E g ) to host the blue phosphorescent emitters and better HOMO and LUMO than PVK for electron and hole injection and transportation of the VSiF model compounds were revealed by density functional theory (DFT) calculations. The preliminary device results in applications of these copolymers as host materials for green phosphorescent emitters demonstrate the copolymers of VSiF and vinylcarbazole have comparable device performance of polyvinylcarazole (PVK), suggesting a bright future of VSiF as building blocks for host materials. vinylsilafluorene, host materials, polyvinylsilafluorene

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The electronic structures and optical properties of oligothiophene substituted spirofluorenes are investigated theoretically with semi-empirical quantum chemical calculations. A theoretical investigation of the interaction between two perpendicular -systems of various oligothiophene substituted spirofluorenes is conducted. The results demonstrate that the interaction between two perpendicular branches is reduced by oligothiophene substitutions. Photoexcitation induced relaxation is mainly located on one of the equivalent branches or the branch with longer conjugation length. In addition to these benefits brought by 9,9-spirobifluorene center, the specific oligothiophene moieties linked to the spiro center also have properties of significant merit, such as the ability to tune energy levels and emission colors by controlling the conjugation length. spirofluorene, OLEDs, AM1, thiophene