Tunable Plasmochromic Devices Using Gold Nanoislands Integrated with an Electropolymerized Organic Semiconductor

The need for the reversible and on-demand reconfiguration of local surface plasmon resonances (LSPR) has driven the emerging field of active plasmonics. The overwhelming majority of electrochromic-polymer-mediated active plasmonic nanostructures consist of lithographically fabricated nanoarrays or colloidal nanoparticles embedded in conductive polymers, such as polyaniline (PANI). Herein, we introduce the semiconducting polymer poly(3-methylthiophene) (P3MT) as a novel tunable dielectric medium for active plasmon control. Likewise, we employ thermally dewetted gold nanoislands (AuNIs) as scalable, cost-effective, and robust plasmonic nanostructures. To date, active plasmonic devices based on P3MT or thermally dewetted nanostructures have yet to be explored. Active plasmonic devices consisting of AuNIs coated with ultrathin 12-15 nm P3MT shells were fabricated and tested. Modulation between reduced and oxidized P3MT resulted in a reversible average LSPR modulation of 22 nm, which compares to or even outperforms other electrochromic polymers at similar shell thicknesses. The plasmochromic performance of P3MT-coated Au nanoislands with various LSPRs and size distributions was evaluated in terms of modulation depth, response time, reversibility, chromaticity, and stability. Cyclic stability measurements reveal that plasmonic shifts can still be observed after 1000 cycles of repeated modulation. This work not only expands the current roster of tunable dielectric media and plasmonic nanostructures for use in active plasmonics but also lays the foundation for next-generation active plasmonic technologies such as tunable organic photovoltaics (OPVs), organic photodiodes (OPDs), and plasmonic field-effect transistors (FETs).