Origins and effects of deep traps in functional group grafted polymeric dielectric materials

Abstract

Introducing deep traps by grafting functional groups on molecular chains of polymeric dielectric materials has been proved as an effective way to improve their electrical properties, especially suppressing the space charge injection and accumulation. However, the underlying physical mechanism of the origins and effects of deep traps on the electrical properties of polymeric dielectrics has not been fully understood. In order to explore the origins and effects of deep traps in grafted polymers, both simulations of electronic band structures as well as 3D electric potential distributions at molecular level and experiments on the macroscopic trap level distributions are carried out. The simulation and experiment results reveal that the deep traps in grafted polymers originate from the different electronic band structures of the grafted polymer compared with the pristine polymer. The deep traps would capture charge carriers and inhibit the charge transport, which leads to decreased conduction current and suppressed space charge injection and accumulation. This work provides a deep understanding of the origins of deep traps in grafted polymers and their effects on the electrical properties, which may guide the rational design of high-performance polymeric dielectric and insulation materials.

Graftable voltage stabilizer for enhancing insulation performance of crosslinked polyethylene

“…Meanwhile, grafted MDVS can introduce local states as trap capture charges in XLPE. 18,44 In order to further verify the origin of deep traps in XLPEg-MDVS from the perspective of chemical structure, the 3D potential distribution of XLPE and XLPE-g-MDVS is established and illustrated in Figure 14. The color blue represents positive electrostatic potential, which can attract holes and act as hole traps.…”

“…It can be seen that grafted MDVS significantly changed the electronic band structure of XLPE, the lowest unoccupied molecular orbital (LUMO) decreased from 2.39 to −2.41 eV, the highest occupied molecular orbital (HOMO) increased from −7.57 to −6.68 eV, and energy gap ( E g ) decreased from 9.96 to 4.27 eV, indicating that XLPE‐g‐MDVS has smaller E g and is easier to be excited and captured electrons. Meanwhile, grafted MDVS can introduce local states as trap capture charges in XLPE 18,44 …”

Dielectric polymers for high-temperature capacitive energy storage

“…21a-c), which can effectively immobilize the injected and excited electrons via strong electrostatic attraction even under high temperatures and high applied fields. 208 The immobilized injected electrons near the electrode/dielectric interface would establish a built-in electric field opposite to the direction of the applied electric field, 209 which suppresses the further charge injection and decreases the Schottky emission conduction current (Fig. 21d-f).…”

Influence of organic additives with electron‐withdrawing and electron‐donating groups on insulation properties of cross‐linked polyethylene at high temperatures for HVDC cable applications

“…The red color reflects the negative electrostatic potential and acts as hole traps. 25 The 4-n-propylbenzoic acid exhibits a more symmetric electrostatic potential distribution and a more concentrated distribution of electron traps and hole traps. Hence, it has a strong ability to trap the charge carriers, resulting in localized deep traps.…”