Molecular Trap Engineering Enables Superior High-Temperature Capacitive Energy Storage Performance in All-Organic Composite at 200 degrees C

Dielectric capacitors are essential components of advanced high-power electrical and electronic systems for electrical energy storage. The drastic reductions in the energy density and the charge-discharge efficiency of dielectric polymers at elevated temperatures, owing to sharply increased electrical conduction, remain a major challenge. While substantial progress has been made in enhancing the high-temperature capacitive performance of dielectric polymers, the improvement has been rather limited when the temperature exceeds 150 degrees C. Here, a universal approach to the control of the energy level of charge traps in all-organic polymer composites by substituent engineering of organic semiconductors, leading to significantly suppressed high-field high-temperature conduction loss and improved capacitive performance is reported. At 200 degrees C, the polymer/organic semiconductor composite delivers ultrahigh energy densities of 3.4 and 5.0 J cm(-3) with an efficiency >90% at 10 and 100 Hz, respectively, outperforming the current dielectric polymers and composites. The underlying mechanism of the improved performance is revealed experimentally and confirmed computationally. Moreover, excellent cyclability and the ability to be fabricated into large-area high-quality films with uniform performance, along with an ultralow filler loading, further demonstrate the potential of molecularly engineered organic semiconductors for dielectric polymer composites operating under extreme conditions.