Mechanism of deep trap sites in epoxy/graphene nanocomposite using quantum chemical calculation

Deep trap sites have been proved able to suppress charge injection into nanocomposites even under high electric field. In order to reveal the mechanism of deep trap sites in epoxy/graphene nanocomposite, the trap distribution was obtained through surface potential decay (SPD) method. The energy levels and 3D potential distributions of epoxy and single-layer graphene under vertical or various parallel electric fields were calculated by using the density functional theory (DFT). The experimental and calculation results indicate that doping with graphene sheets introduces deep trap sites in epoxy/graphene composite. Under parallel electric field, the apparent dipoles of single-layer graphene build positive and negative potential wells in pairs, which capture carriers as the trap sites in epoxy/graphene composite. While a vertical electric field seems to have no effect on the trap sites. For better performance in suppressing charge injection, the doped graphene sheets should be exposed partially to a parallel electric field.