Metasurface‐Assisted Optical Transparency of a Continuous Metal Film

Transparent conductors (TCs) exhibiting simultaneously high electric conductance and high optical transparency are strongly desired in optoelectronic applications. However, TCs realized so far are either based on low‐conductivity materials or nanostructured high‐conductivity noble‐metal films, thus sacrificing electric conductivity, which is unfavorable for applications. Herein, a new configuration of TC, consisting of a continuous metal film sandwiched between two purposely designed metasurfaces is proposed, which can yield high transparency in a predesigned visible regime with high electric conductance preserved by the unstructured metal film. Based on coupled‐mode theory (CMT) analysis, a generic phase diagram to guide the design of such trilayer structures is presented, yielding different performances in terms of peak transmittance and bandwidth. Using a transmitting electron‐beam lithography technology, a series of free‐standing TCs are fabricated, whose optical properties are then characterized experimentally. The best fabricated sample exhibits an optical transmittance of 55.5% at 691 nm, which is five times higher than that of a bare metal film, yet keeping the high electric conductance of a continuous metal film. The findings present a universal methodology for realizing TCs, which should find broad applications in displays, solar cells, and tunable plasmonic filters.