A‐D‐A Structured Molecular Fillers for Boosting High‐Temperature Insulation of Polymer Dielectrics

The rational design of polymer dielectrics capable of robust insulation under extreme electric fields and elevated temperatures remains a formidable challenge for advanced electronic and power systems. Here, we present a class of all‐organic composites incorporating small organic molecules (SOMs) featuring a symmetric acceptor‐donor‐acceptor (A‐D‐A) structure and halogenated end groups. This molecular design promotes strong Coulomb interactions that effectively localize free charges, while pronounced intramolecular charge transfer between excited and ground states enables efficient dissipation of UV energy. Notably, the competition between the ultra‐narrow bandgap and deep charge trapping capacity of the SOMs endows the composites with unique interfacial charge injection suppression at the electrode interface. As a result, the optimized all‐organic composites exhibit a remarkable increase in breakdown strength by 48.72% at room temperature and 78.48% at 120°C, even at ultralow additive concentrations (0.01 wt.%). Both experimental and computational results further validate the long‐term stability of the all‐organic composites under extreme thermal and electrical stress. These findings establish a new molecular design paradigm for high‐performance molecular fillers and open promising avenues for advanced insulation applications in extreme environments.