Scalable Ultrathin All‐Organic Polymer Dielectric Films for High‐Temperature Capacitive Energy Storage

Abstract The miniaturization of electronic devices and power systems for capacitive energy storage under harsh environments requires scalable high‐quality ultrathin high‐temperature dielectric films. To meet the need, ultrasonic spray‐coating (USC) can be used. Novel polyimides with a dipolar group, CF 3 (F‐PI), and all‐organic composites with trace organic semiconductor can serve as models. These scalable high‐quality ultrathin films (≈2.6 and ≈5.2 µm) are successfully fabricated via USC. The high quality of the films is evaluated from the micro‐millimeter scale to the sub‐millimeter and above. The high glass transition temperature T g (≈340 °C) and concurrent large bandgap E g (≈3.53 eV) induced by weak conjugation from considerable interchain distance (≈6.2 Å) enable F‐PI to be an excellent matrix delivering a discharge energy density with 90% discharge efficiency U η90 of 2.85 J cm −3 at 200 °C. Further, the incorporation of a trace organic semiconductor leads to a record U η90 of ≈4.39 J cm −3 at 200 °C due to the markedly enhanced breakdown strength caused by deep charge traps of ≈2 eV. Also, a USC‐fabricated multilayer F‐PI foil capacitor with ≈85 nF (six layers) has good performance at 150 °C. These results confirm that USC is an excellent technology to fabricate high‐quality ultrathin dielectric films and capacitors.