Achieving High Energy Density at 200 °C in All-organic Polyimide Dielectrics Enabled by an Ultra-low Loading Multifunctional Porphyrin Crosslinker

Abstract

High-temperature polymer dielectrics are critically needed for advanced power electronics; however, their performance is often compromised by charge-transfer complexes (CTC) in aromatic polyimides. To overcome this limitation, we introduced an ultra-low loading of 5,10,15,20-tetra(4-aminophenyl) porphyrin (TAPP) as a multifunctional crosslinker into a polyimide (PI) matrix. TAPP simultaneously establishes covalent crosslinking and trap engineering, and its amino groups form a robust network with PI chains, whereas the porphyrin cycle acts as an efficient deep-level charge trap, effectively suppressing CTC formation and charge migration. The optimized PCPI films exhibited a tunable nonmonotonic dielectric constant while maintaining a low loss. The PCPI-0.1 sample shows a significantly enhanced breakdown strength and achieves high discharge energy densities of 8.78, 6.09, and 4.97 J·cm⁻³ at 25, 150, 200 °C, respectively, while maintaining an efficiency above 85%. Remarkably, PCPI-0.1 delivered superior energy density compared to most high-temperature polymer dielectrics reported in the literature, coupled with excellent cycling stability and aging resistance. This work presents a strategy based on ultra-low-loading crosslinking that integrates structural modulation with deep-trap engineering, offering a viable pathway to high-performance all-organic dielectrics for extreme-condition applications.