High Electric Field Conduction of Polymers at Ambient and Elevated Temperatures

The next generation electrical-power and electronic systems with wide band gap semiconductors require thin dielectric films operating under the extreme electric field at elevated temperatures. Here we investigated the conduction properties under high electric field up to 450 MV/m for biaxially oriented polypropylene (BOPP), which is the state-of-the-art commercially available polymer for capacitive applications, as well as three high-temperature polymers poly(ether ether ketone)(PEEK), poly(etherimide)(Ultem) and polyimide(Kapton). Further analysis was performed based on the hopping conduction mechanism. At elevated temperature, the increased thermally-assisted excitation energy gave rise to an increase of the hopping distance. It is argued that the large band gap provided a higher energy barrier to the charge hopping. If the band gap is large enough, the tunneling process dominated the charge transport, i.e., the case of BOPP. For high-temperature applications, both the thermal stability and large band gap are required in order to suppress the temperature and electric field dependent conduction.