Enhanced Dielectric Properties of Polyetherimide‐Based Nanocomposite Films With Doped Semiconductor Traps

ABSTRACT The emerging electronic devices demand dielectric polymer films with high energy storage density over a wide temperature range. However, the mobility of charge carriers leads to unsatisfactory dielectric performance even for heat‐resistant dielectric polymers such as polyetherimide (PEI). Therefore, to enhance the energy storage density of polymer dielectrics, it is critical to concurrently focus on increasing the dielectric constant and improving the breakdown strength by hindering the migration of electrons, which is highly correlated with the intrinsic bandgap structures of dielectrics. Inspired by the tunable bandgap structure of doped semiconductors, this work is aimed at strengthening the trapping of charge carriers depending on the construction of electron traps and the formation of electron–hole pairs, that is, to tailor the bandgap of ZnS 1−x O x via oxygen doping and the band structure at the ZnS 1−x O x /PEI interface region, thereby significantly enhancing the breakdown strength of the composite films. At room temperature and 450 kV mm −1 , the energy density ( U d ) of 0.4 vol% ZnS 0.7 O 0.3 /PEI reaches 5.7 J cm −3 with a charge–discharge efficiency ( η ) of 96.6%, which is 2.3 times that of pure PEI (2.5 J cm −3 , η = 86.2%). Moreover, the composite film exhibits excellent dielectric stability at high temperatures. At 150°C and 350 kV mm −1 , the U d remains 3.4 J cm −3 , with a high η of 89.1%, significantly higher than that of pure PEI (1.5 J cm −3 , η = 80.6%). This work provides a novel perspective for the design of high‐performance dielectric composite films via interfacial engineering.