Double layered design for electromagnetic interference shielding with ultra-low reflection features: PDMS including carbon fibre on top and graphene on bottom

Electromagnetic interference (EMI) shielding materials with low reflection features have become necessary for a new generation of electronic devices to reduce secondary electromagnetic pollution. Here, a novel strategy is adopted to provide flexible polydimethylsiloxane (PDMS) composite films with ultra-low reflection EMI shielding performance by constructing a double-layer structure with uniformly dispersed carbon fibres (CFs) in the upper layer as an impedance-matching absorption layer and continuous graphene fibres (GFs) located at the bottom layer as a conductive reflection layer. The resulting specific structure significantly reduces the reflectivity of the composite film at extremely low carbon conductive fillers (0.01 wt% CFs and 1.00 wt% GFs) through the process of "absorption-reflection-reabsorption" when incident electromagnetic waves (EMWs) pass through the composite film: the total shielding effectiveness (SETotal) achieves 34.4 dB at 18.0 GHz, while the shielding effectiveness of reflection (SER) is only 0.1 dB, and reflection coefficient (R) is as low as 0.018. This phenomenon indicates that 1.8% of the incident EMWs are reflected in the propagation process when 99.96% are attenuated. In addition, the shielding mechanism of the double-layer EMI shielding composite films with low reflection features is studied in depth. This study provides a reliable idea for designing flexible EMI shielding materials with ultra-low reflection to alleviate secondary electromagnetic radiation pollution.