Percolative polymer composites for dielectric capacitors: a brief history, materials, and multilayer interface design

Abstract

High dielectric constant (high-k) polymer composites exhibit great potential in the fields of dielectric-based energy storage and field-effect transistors due to the advantages of easy processing, flexibility and low cost of polymers. Unfortunately, high-k ceramic/polymer composites generally require high filler loadings, exhibiting inferior processing and mechanical properties. A very high k can be achieved for semiconductor/polymer composites with extremely low filler concentrations, but they usually exhibit high dielectric loss, inducing energy wastage and operational risk. In the past decade, considerable progress in reducing dielectric loss has been achieved though materials development and structural design and process engineering. This review first outlines the performance metrics and the history of capacitors and high-k polymer composites, followed by describing the latest developments in new material families, including metals, metal oxides, carbon nanomaterials, 2D (semi-)conductors and conducting polymers. In addition, particular focus is placed on the layered design strategy that can significantly increase the k, breakdown field, and energy density while reducing the dielectric loss and percolation threshold. Also, fundamental insights on them are discussed. The last part of this review is concluded with current challenges and future perspectives of these promising high-k materials and layered design strategy.