Organic Deep-Trap Fillers Enable 250 °C Polymer Capacitors
Polymer capacitors are essential for modern power electronics, but their operation is limited by poor energy density at elevated temperatures. Biaxially oriented polypropylene (BOPP), the industry standard, fails above ~105 °C. This highlight discusses a breakthrough by Yang et al. that uses a generative machine-learning pipeline to discover organic fillers with both wide bandgap (Eg) and high electron affinity (Ea), properties typically mutually exclusive. The model screened over fifty thousand structures to identify more than two hundred high-scoring candidates. Two representatives, 4,6-dinitrobenzene-1,3-dicarbonitrile and 2,4,6-tricyano-1,3,5-triazine, were synthesized, exhibiting Eg ≈ 5.5 eV and Ea ≈ 4.5 eV. Dispersed in a polyimide host, these fillers create deep electron traps that suppress leakage current and delay avalanche breakdown. Composite films achieved an energy density of 5.1 J cm−3 at 250 °C with 90% efficiency, outperforming conventional polymers. The team scaled production using a roll-to-roll line, producing kilometer-scale films with uniform dispersion. This work demonstrates a viable path to high-temperature polymer capacitors for traction inverters and DC-link applications.