Synthesis, Photophysics, and Electroluminescent Performance of Stable Blue-Light-Emitting Copoly(9,9-diarylfluorene)s

A series of fluorene derivatives containing nonsymmetric and bulky aromatic groups at C-9 position were synthesized and used for the preparation of blue-light-emitting copolyfluorenes (P1-P4) by the Suzuki coupling polycondensation. The copolymers were characterized by molecular weight determination, elemental analysis, differential scanning calorimeter, thermogravimetric analysis, absorption and emission spectroscopy, cyclic voltammetry, and differential pulse voltammetry. Their decomposition temperatures and glass transition temperatures are 423-441 degrees C and > 120 degrees C, respectively. In film state, the copolyfluorenes exhibit blue photoluminescence at 425-450 nm, which remains almost unchanged after annealing at 200 degrees C in air for 60 min. Polymer light-emitting diodes [ITO/PEDOT:PSS/P1-P4/Ca(50 nm)/A(100nm).] A show stable blue-light emission under device operation with the CIE coordinates being between (0.16, 0.07) and (0.17, 0.09). The light-emitting diodes devices from P1 and P3 containing electron-deficient oxadiazole units display enhanced performance, with the maximum brightness and maximum current efficiency being (4510 cd/m(2) and 2.40 cd/A) and (2930 cd/m(2), 1.19 cd/A), respectively. (c) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2821-2834, 2009