Synthesis of Poly(9,9-diallylfluorene) and the Mechanism of Its Single Green Emission

Abstract

Poly(9,9-diallylfluorene) (PAF) with single green emission was synthesized through polymerization of allyl substituted 2,7-dibromofluorene in the presence of NiCl2 as the catalyst. PAF shows deep blue fluorescence at 403 nm in solution and 456 nm in solid film state. The organic electroluminescence device (OLED) gives a green emission with the peak at 532 nm by using PAF as the emitter with a structure of ITO/PEDOT:PSS/PAF/LiF/Al (ITO: indium tin oxides; PEDOT: poly(3,4- ethylenedioxythiophene); PSS: poly(styrenesulfonate)). The photoluminescence (PL) of the PAF film red- shifted after thermal anealing, the original peak of blue emission decreased and a new peak of green emissioin increased. However, there is no change in the chemical structure based on the Fourier transform infrared (FT-IR) spectra of PAF after thermal annealing under vacuum. Moreover, there is no change on the PL spectra of PAF before and after the evaporation of metal cathode. It can be deduced that the single green emisson of PAF based OLED is original from the inter-chain aggregation which can be confirmed from their atomic force microscopy (AFM) images.