Significantly improved high-temperature capacitive performance in polymer dielectrics utilizing ultra-small carbon quantum dots with Coulomb-blockade effect

Advanced electronic equipment requires polymer film capacitors to work under harsh temperature and electric field conditions. However, the inevitable deterioration of the insulation performance with electric field and temperature will limit the improvement of high-temperature capacitive performance. Herein, we report a novel sandwich-structured dielectric nanocomposite, utilizing microwave radiation in-situ to synthesize subminiature carbon quantum dots (CQDs) in the middle layer. Comprehensive simulation and experimental results confirm that CQDs, as an electronic barrier, prevent carriers from passing through the interlayer, thereby significantly reducing the leakage current in the polymer matrix at high temperatures, and obtaining excellent breakdown strength. Thanks to the slightly increased dielectric constant and significantly reduced energy loss, the nanocomposites with the optimal loading exhibit an excellent discharged energy density of 4.10 J cm-3 with efficiency above 90 % at 200 degrees C, which is far superior to most current dielectric nanocomposites. We believe that this simple and economic strategy provides a new idea for the development of green dielectric capacitors.