Electronic structures of planar and nonplanar polyfluorene

Abstract

Polyfluorene is well known as an efficient blue emitter for polymer-based light-emitting diodes and is very attractive from a physical point of view because randomly twisted, regularly twisted, or planar conformations can be realized in its solid state. In this chapter, the relationship between its optical properties and the polymer conformation is discussed within the framework of the simple effective conjugation length model. The electronic structure of polyfluorene is also discussed based on the electroabsorption (EA) spectra of the three conformations. Different from other conjugated polymers, polyfluorene exhibits complicated EA spectra in its highly ordered thin films. From the analysis of these EA spectra, the similarities and differences in the electronic structure between polyfluorene and other conjugated polymers are clarified.