Synthesis and WORM Memory Effect of a Donor Acceptor Polymer with an Integrated Fluorene and Triphenylamine Backbone

A novel highly soluble donor acceptor polymer, poly［4,4′-(4.4′ (9H fluorene 9,9 diyl)bis(4,1- phenylene))bis(oxy)diphthalonitrile］［triphenylamine］［9,9-dioctyl 9H fluorene］(PFTD), was designed and synthesized through the Suzuki coupling reaction. The fluorescence intensity of PFTD decreased as the solvent polarity increased. Its emission band was observed to get broader and red shifted (λ=426 nm (toluene), 432 nm (THF), 442 nm(PhCN) and 445 nm (DMF)). The absolute fluorescence quantum yield of PFTD changed from 47.8% for a dilute THF solution to 5.5% for a thin film due to the existence of a strong fluorescence quenching effect in the solid state. The HOMO, LUMO, band gap, IP and EA values experimentally estimated from the onset of the redox potentials were -5.43, -2.62, 2.81, 5.69, 2.88 eV, respectively. The PFTD film was attached to aluminum and indium tin oxide contacts to fabricate a memory device with typical bistable electrical switching, non volatile write once read many times (WORM) memory performance, a turn on voltage of approximately -1.5 V and an ON/OFF ratio of more than 104.