Chiral Plasmonic Nanocavities Enable Efficient Circularly Polarized Luminescence through Tailored Optical Chirality

Ultrastrong enhancement of circularly polarized luminescence (CPL) is achieved with chiral plasmonic nanocavities made of helicoid-on-mirror structures. The large local optical chirality enhancement, along with local electric field enhancement in the ultrathin chiral nanocavities, generates prominent chiral photoluminescence with a dissymmetric factor (glum) of up to ∼0.6 and a quantum yield (QY) of ∼29%. Such a large chiroptic enhancement is correlated to the morphology of the helicoids, where the sharp corners strongly enhance the local E-field (∼500) and optical chirality (∼90). This chiral plasmonic nanocavity can also be applied to enhance the CPL of a chiral dye (R/S-1) with an emission band off the plasmon resonance, which leads to a 4-fold enhancement of its glum (∼0.2) and QY up to ∼60%. This superior enhancement strategy not only demonstrates the synergistic enhancement of both QY and glum but also provides a promising route toward superior CPL devices for practical applications.