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

ABSTRACT 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.