Scalable Polymer Composites Enhanced by Trace-Amount Polymer Semiconductor for High-Performance Capacitive Energy Storage at 250°C

High-temperature polymer dielectrics are critically needed for capacitive energy storage in next-generation power electronics operating above 200 °C, yet their practical application is severely limited by thermally activated charge transport that leads to exponentially increased conduction loss and premature breakdown. Here, we report a polymer solid-solution strategy that simultaneously preserves intrinsic insulation while elevating trap energy levels through the incorporation of an ultralow fraction of a linear semiconducting polymer. The semiconducting chains are molecularly dispersed, functioning as electronic structure modulators rather than transport pathways. The simple nitrogen-containing conjugated segments generate deep localized traps with high positive electrostatic potential, which immobilize injected electrons by increasing the high-energy-level trap density and suppressing hopping conduction at elevated temperatures. Consequently, the composite exhibits a 1940% enhancement in capacitive performance relative to the pristine polymer, while maintaining ≥90% charge–discharge efficiency. The fully organic solid-solution films simultaneously achieve a high energy density of 3.9 J cm −3 and 90% efficiency at 250 °C, together with ultrahigh long-term stability. This work establishes a distinct route for decoupling insulation from trap engineering in polymer dielectrics and provides a scalable, low-cost platform for high-temperature energy storage applications.