Sandwich-structured long-wave infrared transparent electromagnetic shielding film using transmittance-enhanced wetting layer/Ag stacked conductive layers

Designing infrared transparent electromagnetic shielding films (ITESFs) is challenging because carrier absorption and carrier transport occur simultaneously. Sandwich structures with Ag inserted into semiconductors can achieve synergy between transparency and electromagnetic shielding effectiveness, but Ag films alone suffer from island growth and optical loss. This work presents a sandwich structure using a transmittance-enhancing conductive layer composed of a wetting layer and Ag (WL/Ag). As a proof of concept, a Bi₂Se₃/Ti WL/Ag/Bi₂Se₃ film was prepared, achieving a long-wavelength infrared transmittance of 77% and a conductivity of 5988 S/cm. The electromagnetic shielding effectiveness reached ∼22 dB in the X band (8.2–12.4 GHz), meeting the requirement of protecting infrared optoelectronic devices from electromagnetic interference. High-resolution transmission electron microscopy and theoretical calculations showed that the Ti wetting layer enhances performance through high surface energy, low nk product values, and admittance matching. We proposed design criteria for wetting layers and identified candidate materials such as Cr. This study provides an optimization strategy for sandwich structures and introduces high-performance ITESFs for infrared optoelectronic devices.