On August 6, Associate Professor Li Qi and Professor He Jinliang from the Department of Electrical Engineering of Tsinghua University published the title "High Temperature Capacitor Film Based on Polymer-Molecular Semiconductor All-Organic Composite Material" in the journal Nature Communications (Polymer /molecular semiconductor all-organic composites for high-temperature dielectric energy storage), the first all-organic composite film with high-efficiency dielectric energy storage at 200 degrees Celsius was developed. The dielectric energy storage performance of this kind of all-organic composite dielectric materials at a high temperature of 200 degrees Celsius not only far exceeds the current best high-temperature polymers and polymer nanocomposite dielectric materials, but also close to the room temperature performance of commercial polymer capacitor films ; While greatly improving the characteristics of high-temperature dielectric energy storage, it also realizes the preparation of large-area and uniform films, which provides the possibility to realize the application of film capacitors under the harsh temperature environment of 200 degrees Celsius.
Polymer film capacitors have the advantages of high dielectric strength, low energy loss and good self-healing properties, and their market share in the global industrial capacitor market exceeds other types of capacitor products. However, the insulation performance of polymer dielectric materials is extremely sensitive to temperature. Under the action of high temperature and high electric field, the leakage current increases exponentially and the discharge efficiency drops sharply, which eventually causes the capacitor to be overheated and damaged. At present, mainstream commercial film capacitors only work below 105 degrees Celsius, and long-term operating temperatures are below 70 degrees Celsius. On the other hand, with the continuous increase in the power of electronic devices and power and energy equipment and the continuous pursuit of miniaturization and compact power modules, the operating temperature requirements of electronic materials have rapidly increased, and film capacitor dielectric materials have become high-temperature electronic devices and The technical bottleneck of the equipment.
This paper adopts a completely different technical route from the previous method-the use of the strong electronic ability of the electron acceptor material in organic photovoltaics to realize the construction of deep charge traps in high-temperature polymers. This organic molecular semiconductor electron acceptor material has extremely high electron affinity, and is widely used in organic photovoltaics to efficiently separate excitons at the heterojunction interface. They can produce a strong binding effect on free electrons through the extremely uneven distribution of electrostatic potential on their surface. An all-organic composite high-temperature dielectric material is prepared by doping a very small amount of high electron affinity organic molecular semiconductor into a heat-resistant polymer. Under the conditions of 200 degrees Celsius and 200kV/mm electric field, the resistivity of this type of material is more than two orders of magnitude higher than that of high temperature polymers; the energy density of 200 degrees Celsius and discharge efficiency of more than 90% is 2.3 of the best polymer high temperature dielectric materials. Times. In addition, the all-organic composite system solves the problems of uneven dispersion of high surface energy particles and introduction of interface defects in the traditional organic-inorganic composite system, and has significant advantages in film quality and large-scale preparation.