Filler-Free Conducting Polymers as a New Class of Transparent Electromagnetic Interference Shields

Abstract

Transparent electromagnetic interference (EMI) shields are increasingly in demand for medical, military, wireless networks, aerospace electronics, and navigation control systems. To date, researchers have mixed pristine and/or doped conductive polymers with carbon allotropes and metallic fillers to increase the total shielding effectiveness, compromising the transparency, amount of the materials used, and weight of the shields. Obtaining cost-effective and transparent EMI shields without the need to incorporate fillers is extremely desirable. Herein, we implement a design strategy for fabricating a gigahertz (GHz) highly transparent shield made of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The total EMI shielding effectiveness of 15 dB is achieved in the X-band frequency range for a 50 nm ultrathin film with a high transparency of 97.1%. The fabricated filler-free EMI shield holds a record thickness-specific shielding figure-of-merit of 300 dB μm-1-far exceeding the best values for micron-thick silver-, carbon-, and MXene-based composite material shields-with even a higher transparency. The feasibility of the developed filler-free shield for large-scale applications is validated by its integration into a cell phone display glass, as a prototype, in which the EMI shielding effectiveness elevates to 18.3 dB.