High-Temperature Dielectric Energy Storage in All-Organic Composite Films Enabled by Molecular Semiconductor Fillers

Polymer dielectrics suffer from severe conduction losses under coupled thermal-electrical stresses, limiting their practical applications in film capacitors under harsh conditions. Incorporation of organic molecular semiconductor fillers with concurrently high electron affinity (Ea) and large bandgap (Eg) into the polymer matrix represents a promising modification strategy, although only limited semiconductor fillers have been reported. Here, we report an all-organic high-temperature dielectric composite where an alternative molecular semiconductor tetracyanobenzene characterized by an Ea of 3.92 eV and Eg of 4.65 eV is used. Experimental results demonstrate that the trap density is significantly increased, which effectively suppresses leakage current and leads to a marked enhancement in breakdown strength. Consequently, the polyimide-based composite film exhibits a high discharged energy density (6.92 J cm–3) with a high charge–discharge efficiency (90.32%) at 150 °C. This outperforms most currently existing all-organic and nanocomposite dielectric polymers, thereby offering a facile yet effective strategy for the design of high-temperature dielectric polymers.