Charge trapping in the films blended with polystyrene and different cyano-substituted spirofluorenes organic small molecules

We investigated the charges trapping and retention processes of the blend electret films of polystyrene and different cyano-substituted spirofluorenes organic small molecular material (PS/SFXs) by using atomic force microscopy and Kelvin probe force microscopy technologies. The series of blend films present a promising charge storage property and a potential application in the charge trapping memory devices. We focused on the influences of the prepared parameters and the storage conditions for the samples on their charge storage properties. We found that water molecules in the films will influence the injection and retention processes of the trapped charges in the blend PS/SFXs films. The enhanced localization ability of the trapped charges is observed in the film prepared with high annealing temperature. The thicknesses of the films have an obvious effect on the charge injection process while having no discernible effect on the retention process. These results are very important for the studies of PS/SFXs in memory devices. The results show that the polarization and net charge transfer coexist for charge trapping in PS/SFXs films, while the symmetry of molecular structure of SFXs plays an important role in trapped charges stability.