Enhanced Photoluminescence of Monolayer MoSe₂ in a Double Resonant Plasmonic Nanocavity with Fano Resonance and Mode Matching

Abstract

Two‐dimensional transition metal dichalcogenides exhibit remarkable optical properties. However, their applications in electronics and photonics are severely limited by the intrinsically low absorption and emission rates. Here, the photoluminescence (PL) enhancement by integrating the monolayer MoSe2 into an Ag nanowire‐on‐mirror (NWoM) nanocavity is reported. From the dark‐field scattering spectrum, a Fano resonance resulting from the coupling between discrete exciton state of MoSe2 and broad plasmon mode of nanocavity is observed. This Fano resonance, as a characteristic of intermediate plasmon–exciton coupling, shows remarkable ability to accelerate emission rate of MoSe2. Furthermore, the nanocavity with multiple resonances provides an excellent spatial mode overlap at excitation and emission wavelengths that affords the intriguing opportunity to resonantly enhance the absorption and PL quantum yield at the same location. The combination of Fano resonance and mode matching allows the attainment of over 1800‐fold PL enhancement. These results provide a facile way to enhance the PL intensity of monolayer MoSe2 that may facilitate highly efficient optoelectronic devices.

Excitation and emission distinguished photoluminescence enhancement in a plasmon–exciton intermediate coupling system

“…The capability of plasmonic nanostructures to confine light into deep subwavelength volumes can dramatically improve the light absorption and emission performances of monolayer TMDCs. PL enhancement of monolayer TMDCs has been reported in several coupling systems, such as Au nanorods and WS 2 , 24,25 Ag nanocubes on Au film and MoS 2 or WSe 2 , [26][27][28][29] Ag NWs on Au film and MoSe 2 , 30 Au nanospheres or nanosphere dimers on Au film and MoS 2 , 31,32 and metal nanostructure arrays and MoS 2 or WSe 2 . [33][34][35][36] Among a variety of plasmonic nanostructures, the coupled structure of a metal nanoparticle and a metal film is widely used, which is usually called nanoparticle-on-mirror (NPOM), due to its easy fabrication, ultrasmall mode volume, and readily tailored optical resonance over a wide spectral range.…”

“…37 In addition to PL enhancement, strong or intermediate coupling of the plasmon mode with one exciton state has been demonstrated in the coupled systems of NPOMs and monolayer TMDCs. [28][29][30][38][39][40] In spite of the progress, the strong coupling of multiple exciton states in monolayer TMDCs with plasmonic nanogap mode has not been explored yet. Moreover, while most studies were aimed to achieve a high PL enhancement factor, less effort has been devoted to experimentally disentangling the plasmon resonance dependent contributions of excitation enhancement and emission enhancement to the enhanced PL intensity.…”

Resonance Photoluminescence Enhancement of Monolayer MoS2 via a Plasmonic Nanowire Dimer Optical Antenna

“…Atomically thin transition-metal dichalcogenides (TMDs) such as MoS 2 , − direct-band-gap two-dimensional materials, have attracted great interest and exhibited promising applications in field-effect transistors, , solar cells, photodetectors, − light-emitting devices, strong-coupling regimes, plasmon–exciton coupling and surface-enhanced Raman scattering (SERS), , due to their extraordinary physical properties. Nevertheless, their low quantum efficiency and weak light absorption have been bottlenecks in these applications.…”

Strong Linearly Polarized Light Emission by Coupling Out-of-Plane Exciton to Anisotropic Gap Plasmon Nanocavity

“…In principle, such field enhancement can be further optimized by reducing the thickness of the InSe flake. Moreover, replacing the symmetric nanocubes with an anisotropic nanowire structure should lead to polarization-dependent emission from InSe that is preferred for developing polarized light-emitting diode. − …”