Graphene/Polyelectrolyte Layer-by-Layer Coatings for Electromagnetic Interference Shielding

TL;DR

This paper presents a spray, layer-by-layer coating method using reduced graphene oxide and polyelectrolyte to create thin, conductive, and highly effective electromagnetic interference shielding layers with thicknesses in the micron range.

Contribution

It introduces a novel spray, layer-by-layer fabrication technique for micron-thick, highly conductive EMI shielding coatings with exceptional effectiveness, surpassing previous thicker materials.

Findings

Achieved EMI shielding effectiveness >4830 dB/mm.

Maximum EMI SE of 29 dB for 6 μm thick coating.

Electrical properties strongly depend on graphene flake size.

Abstract

Electromagnetic interference (EMI) shielding coating materials with thicknesses in the microscale are required in many sectors, including communications, medical, aerospace and electronics, to isolate the electromagnetic radiation emitted from electronic equipment. We report a spray, layer-by-layer (LbL) coating approach to fabricate micron thick, highly-ordered and electrically-conductive coatings with exceptional EMI shielding effectiveness (EMI SE >4830 dB/mm), through the alternating self-assembly of negatively-charged reduced graphene oxide (RGO) and a positively-charged polyelectrolyte (PEI). The microstructure and resulting electrical properties of the (PEI/RGO)n LbL structures are studied as function of increasing mass of graphene deposited per cycle (keeping the PEI content constant), number of deposited layers (n), flake diameter and type of RGO. A strong effect of the lateral flake dimensions on the electrical properties is observed, which also influences the EMI SE. A maximum EMI SE of 29 dB is obtained for a 6 um thick (PEI/RGO)10 coating with 19 vol.% loading of reduced electrochemically-exfoliated graphene oxide flakes with diameters ~3um. This SE performance exceeds those previously reported for thicker graphene papers and bulk graphene/polymer composite films with higher RGO or graphene nanoplatelets contents, which represents an important step towards the fabrication of thin and light-weight high-performance EMI shielding structures.