Copolyfluorenes Containing Bridged Triphenylamine or Triphenylamine: Synthesis, Characterization, and Optoelectronic Properties

A novel aryl-bridged triphenylamine derivative, 7-t-butyl-5,5,9,9-tetraaryl-13b-aza-naphtho[3,2,1-de]anthracene (ABTPA) was designed and synthesized. The alternating copolymers of ABTPA/dihexylfluorene (P1) and triphenylamine (TPA)/dihexylfluorene (P2) were synthesized by Suzuki coupling reaction. P1 shows excellent thermal stability with a decomposition temperature of 440 degrees C and a glass-transition temperature of 326 degrees C. The HOMO energy levels of the two polymers are very close (-5.15 eV for P1 and -5.13 eV for P2). The maximum absorption peak of P1 is red shifted by 23 nm with respect to P2, because the incorporation of ABTPA units into the PF backbone enhances the electronic conjugation degree compared with the case of TPA units. The rigidity and the steric hindrance of the ABTPA in P1 result in a small Stokes shift and almost the same emission spectra of P1 between its film and solution. A PLED with simple configurations of ITO/PI/TNS (tetranaphthalen-2-yl-silane)/Alq(3) (tris(8-hydroxyquinolinolato)aluminum)/Al emits a blue light with emission peak at 436 nm, and exhibits a maximum current efficiency of 1.89 cd/A and a maximum luminance of 4183 cd/m(2), which is superior to the device with P2 as emissive layer under the identical conditions. These results indicate that ABTPA unit could be a very promising candidate to replace TPA unit and find widely application in organic/polymeric optoelectronic materials. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3651-3661, 2009