Enhancing energy storage performance of polymer composites with molecular semiconductors

Abstract

With the ever-increasing demand for advancing clean energy technologies, efficient energy storage devices have attracted significant attention in both research and industrial fields. Dielectric capacitors have advantages of high power density, rapid discharge rates, and excellent stability. Compared to inorganic ceramic materials, polymer-based dielectrics are favored for the fabrication of high-energy capacitors due to their elevated operating voltages and flexible processing capabilities. In this study, the P(VDF-CTFE) polymer matrix is combined with molecular semiconductors, specifically PCBM and ITIC, to enhance the breakdown strength and energy storage density of composite film materials. The introduction of molecular semiconductors promotes the formation of the α phase and improves crystallinity, which in turn contributes to the reduction of dielectric loss and the enhancement of efficiency. With the addition of 1.1 wt% PCBM, the polymer composite dielectric achieves an impressive breakdown strength of 490 MV/m, an energy density of 17 J/cm³ , and a charge-discharge efficiency of 76 %. In comparison, doping with 0.3 wt% ITIC results in a breakdown strength of 409 MV/m, a lower energy density of 8.7 J/cm³ , and a charge-discharge efficiency of 50 %. The introduction of molecular semiconductors creates trap states and inhibits carrier mobility in the polymer composites, thereby effectively enhancing the breakdown strength. The molecular semiconductor PCBM, with its higher electron affinity and larger bandgap, is more favorable for optimizing the energy storage performance of the polymer composite materials.