Flash-Memory Effect for Polyfluorenes with On-Chain Iridium(III) Complexes

Polyfluorenes containing Ir(III) complexes in the main chain are demonstrated to have promising application in a polymer memory device. A flash-memory device is shown whereby a polymer solution is spin-coated as the active layer and is sandwiched between an aluminum electrode and an indium tin oxide electrode. This device exhibits very good memory performance, such as low reading, writing, and erasing voltages and a high ON/OFF current ratio of more than 10(5). Both ON and OFF states are stable under a constant voltage stress of -1.0 V and survive up to 10(8) read cycles at a read voltage of -1.0 V. Charge transfer and traps in polymers are probably responsible for the conductance-switching behavior and the memory effect. The fluorene moieties act as an electron donor and Ir(III) complex units as the electron acceptor. Furthermore, through the modification of ligand structures of Ir(III) complex units, the resulting polymers also exhibit excellent memory behavior. Alteration of ligands can change the threshold voltage of the device. Hence, conjugated polymers containing Ir(III) complexes, which have been successfully applied in light-emitting devices, show very promising application in polymer memory devices.