Enhanced energy density at elevated temperature in polyetherimide based all-organic dielectrics via UV irradiation

The rapid development of electrostatic capacitors puts forward more stringent requirements for the use of polymer dielectrics, that is, to maintain high energy storage density and efficiency under extreme environments of high temperature and high electric field. In this work, all-organic composites comprising polyetherimide (PEI) blended with high-electron-affinity polymer dots (PDs) have been fabricated and modified by UV irradiation. It is found that the UV irradiated all-organic composites exhibit high energy density (4.1 J cm−3), far outperforming pristine PEI. The energy level diagram and electric conduction results prove that PDs capture free electrons via electrostatic attraction and the wide bandgap forms a barrier to electron transport, which inhibits the electric conduction, leading to the substantial performance improvements. This work demonstrates an effective modification method for the improvement of high-temperature electronics and energy storage devices.