Synthesis and enhanced efficiency of organic light-emitting materials

Abstract

Firstly, two novel organic-inorganic hybrid polyfluorene derivatives, PFDOPPOSS and PFT2POSS, were synthesized by the Pd-catalyzed Suzuki reaction of POSS (polyhedral oligomeric silsesquioxane) appended fluorene, dioctyl phenylene, and bithiophene moieties. Photoluminescence (PL) studies showed that the incorporation of the POSS pendant into the polyfluorene derivatives significantly enhanced the fluorescence quantum yields (ΦFL) of the polymer films, likely via a reduction in the degree of interchain interaction as well as keto formation. Additionally, the blue light emitting polyfluorene derivative PFDOPPOSS showed high thermal color stability in PL. Moreover, single-layer LED devices of configuration ITO/PEDOT:PSS/polymer/Ca/Al fabricated using PFDOPPOSS and PFT2POSS showed highly improved brightness, maximum luminescence intensity and quantum efficiency compared to devices fabricated using the corresponding pristine polymers PFDOP and PFT2. In particular, the maximum external quantum efficiency of PFT2POSS was 0.13 %, which is twice that of PFT2 (0.06 %), and the maximum current efficiency of PFT2POSS was 0.38 cd/A, which again twice that of PFT2 (0.19 cd/A). Secondly, a new series of highly bright and efficient poly(p-phenylenevinylene)s (PPV)s based on POSSs was synthesized via the Gilch polymerization. The three POSS-containing PPVs are as follows: POSS05-PPV(containing 5 mol % POSS-appended PPV units), POSS25-PPV, and POSS100-PPV. The POSS-containing PPVs exhibit higher glass transition temperatures (64-77oC) than that of MEH-PPV (58oC), indicating that electroluminescence (EL) devices fabricated with these polymers should have good thermal stabilities. As the POSS content ratio in the polymers increases, the maximum wavelengths of the UV-vis absorption and PL emission spectra are increasingly blue-shifted except for those of POSS05-PPV. The LED devices based on the POSS-containing PPVs were found to exhibit maximum EL wavelengths ranging from 577 to ...