Polariton Dynamics in Two-Dimensional Ruddlesden–Popper Perovskites Strongly Coupled with Plasmonic Lattices

Abstract

Strong coupling between light and matter can produce hybrid eigenstates known as exciton–polaritons. Although polariton dynamics are important photophysical properties, the relaxation pathways of polaritons in different coupling regimes have seen limited attention. This paper reports the dynamics of hybridized states from 2D Ruddlesden–Popper perovskites coupled to plasmonic nanoparticle lattices. The open cavity architecture of Al lattices enables the coupling strength to be modulated by varying either the lead halide perovskite film thickness or the superstrate refractive index. Both experiments and finite-difference time-domain simulations of the optical dispersion diagrams showed avoided crossings that are a signature of strong coupling. Our analytical model also elucidated the correlation between the exciton/plasmon mixing ratio and polariton coupling strength. Using fs-transient absorption spectroscopy, we found that both the upper and lower polaritons have shorter lifetimes than the excitons and that polaritons can show faster excited-state dynamics when they have access to additional energy transfer channels.

Polariton Formation from Soret Band Excitons in Metal–Organic Frameworks and Plasmonic Lattices

“…Additionally, the polariton modes are in good agreement with the values predicted from the Jaynes–Cummings model (λ = 450 and 400 nm for LP and UP, respectively). The splitting between the UP and LP bleach signals is 324 meV, which is well above previously reported Rabi splitting for SLR-exciton strong coupling. ,,, Based on losses (γ pl , γ 0 ) determined from the fwhm of the uncoupled Soret band (240 meV) and SLR (70 meV), the Rabi splitting satisfies both 2 g > (γ pl + γ 0 )/2 and the stricter 2 g > γ pl , γ 0 conditions required to reach the strong coupling regime …”

“…The splitting between the UP and LP bleach signals is 324 meV, which is well above previously reported Rabi splitting for SLR-exciton strong coupling. 13,25,29,35 Based on losses (γ pl , γ 0 ) determined from the fwhm of the uncoupled Soret band (240 meV) and SLR (70 meV), the Rabi splitting satisfies both 2g > (γ pl + γ 0 )/2 and the stricter 2g > γ pl , γ 0 conditions required to reach the strong coupling regime. 36 The amplitude-averaged lifetimes of the UP (99 ± 26 ps) and LP (78 ± 42 ps) are less than the uncoupled MOF, while the middle bleach signal has a lifetime within error of the uncoupled MOF (250 ± 69 ps).…”

Enhanced Two-Dimensional Exciton Propagation via Strong Light–Matter Coupling with Surface Lattice Plasmons

“…22,24 SLRs can propagate in the plane of the array coherently at nearly the speed of light and are delocalized over more than 100 μm. 24−26 Formation of exciton−polaritons has been observed when coupling plasmonic NP arrays with organic molecules, 27−30 metal−organic frameworks (MOFs), 31 quantum dots, 32,33 carbon nanotubes, 34,35 2D Ruddlesden−Popper phase perovskites, 36 and transition metal dichalcogenides (TMDCs). 37,38 Among the excitonic materials allowing room-temperature exciton−polariton operation, 2D perovskites are of great interest because of their structural versatility, ease of fabrication, and high oscillator strength that promotes strong coupling.…”

“…39 Moreover, the self-assembled multiquantum well structure allows a tunable thickness while maintaining stable direct excitons, which can be useful to tune the coupling strength. 12,36,40 2D perovskites have been employed to demonstrate polariton condensation and strong polariton interaction in FP cavities 41,42 but with few reports of the exciton−polariton on plasmonic arrays. 36 Specifically, how exciton transport is modified via strong light−matter interactions is largely unknown.…”

“…12,36,40 2D perovskites have been employed to demonstrate polariton condensation and strong polariton interaction in FP cavities 41,42 but with few reports of the exciton−polariton on plasmonic arrays. 36 Specifically, how exciton transport is modified via strong light−matter interactions is largely unknown. Because the polaritonic states have lifetimes of 100s of femtoseconds or shorter, questions remain regarding the time and length scale of the coherent transport.…”