Improved Capacitive Energy Storage at High Temperature via Constructing Physical Cross-Link and Electron–Hole Pairs Based on P-Type Semiconductive Polymer Filler

In this work, p-type polymer semiconductor poly(2-((3,6,7,10,11-pentakis (hexyloxy) triphenylene-2-yl)oxy)ethyl methacrylate) (PMHT) is added into polyetherimide (PEI). Benefiting from the electrostatic interaction between strong electrophilic charged phenyls of the PEI matrix and strong electronegative benzophenanthrene unit of the PMHT filler, the physical cross-linked networks are formed in polymer blends. Meanwhile, the lowest unoccupied molecular orbital level of PEI is close to the highest occupied molecular orbital level of PMHT, which is easy to establish electron–hole pair by Coulomb force. Thus, the carrier trap is constructed in the heterojunction region between PMHT filler and PEI matrix. Both physically cross-linked networks and electron–hole pairs can promote breakdown strength (E_b) of PEI and decrease energy loss. Importantly, PMHT filler can improve the dielectric constant of PEI. As a result, 0.75 wt% PMHT/PEI delivers an ultrahigh discharge energy density (U_d) of 10.7 J cm⁻³ at an E_b of 680 MV m⁻¹ and at room temperature, and maintains a charge and discharge efficiency of above 90%. In addition, a superior U_d of 5.1 and 3.3 J cm⁻³ is achieved at 150 and 200 °C, respectively. This paper creates a new perspective for preparing high-properties polymer dielectrics by combining the advantages of cross-linking and electron–hole pairs.