Electronic memory effects in diodes of zinc oxide nanoparticles in a matrix of polystyrene or poly(3-hexylthiophene)

Electronic memory effects in metal-insulator-metal devices with aluminum and poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) as electrodes and a solution processed active layer consisting of zinc oxide (ZnO) nanoparticles embedded in a matrix of poly(3-hexylthiophene) or polystyrene are investigated. After an initial forming process, the devices show a reversible change in conductivity. The forming process itself is interpreted in terms of desorption of molecular oxygen from the ZnO nanoparticle surface, induced by injection of holes via the PEDOT:PSS contact, leading to a higher n-type conductivity via interparticle ZnO contacts. The forming can also be induced with ultraviolet light and the process is studied with electron paramagnetic resonance, photoinduced absorption spectroscopy, and field effect measurements. Also, the composition of the active layer is varied and the memory effects can by influenced by changing the ZnO content and the polymer, allowing for data storage with lifetime >14h.