New copolyfluorenes (PFDO.5-50) of 9,9-1-dihexylfluorene and 2-(2,6-bis(4-(2-phenyl-2-cyanovinyl)-2,5-bis(hexyloxy)styryl)-4// -pyran-4-ylidene)malononitrile (DCM) were synthesized by the Suzuki coupling reaction. They were characterized by molecular weight determination, elemental analysis, FT-IR spectroscopy, DSC, TGA, absorption and emission spectroscopy, and cyclic voltammetry (CV). The copolymer films showed absorption peaks at 383-397 and 481-496 nm, and PL peaks at 421-424 and 560-596 nm originated from fluorene and DCM segments, respectively. The longer wavelength PL peak red-shifted gradually from 560 to 596 nm with increasing DCM contents (0.83%-49.8%). The LUMO energy levels lowered as the content of DCM units increased ( - 2.75 eV→ - 3.70 eV), whereas the HOMO levels remained almost unchanged (-5.68 eV→ - 5.64 eV). Electroluminescent devices, ITO/PEDOT:PSS/polymer/Ca(50 nm)/Al(150 nm), were fabricated to investigate the influence of DCM contents on emission characteristics. The maximum brightness and current efficiency of the PFD0.5 device (1719 cd/m2 and 0.25 cd/A) surpassed those of the PF device (1012 cd/m2 0.17 cd/A). With an increase in DCM content, the current efficiency was further increased to 0.30 cd/A at about 5% DCM units. The EL emission of PFD5-PFD50 was exclusively originated from DCM fluorophores (>550 nm) due to rampant energy transfer. However, simultaneous emission of PF and DCM segments was readily obtained by lowering DCM contents (PFD0.5, PFDl, or by blending PFD0.5 with PF).
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry