Exciton‐Polaritons and Their Bose–Einstein Condensates in Organic Semiconductor Microcavities

Abstract

Exciton‐polaritons are half‐light, half‐matter bosonic quasiparticles formed by strong exciton–photon coupling in semiconductor microcavities. These hybrid particles possess the strong nonlinear interactions of excitons and keep most of the characteristics of the underlying photons. As bosons, above a threshold density they can undergo Bose–Einstein condensation to a polariton condensate phase and exhibit a rich variety of exotic macroscopic quantum phenomena in solids. Recently, organic semiconductors have been considered as a promising material platform for these studies due to their room‐temperature stability, good processability, and abundant photophysics and photochemistry. Herein, recent advances of exciton‐polaritons and their Bose–Einstein condensates in organic semiconductor microcavities are summarized. First, the basic physics is introduced, and then their emerging applications are highlighted. The remaining questions are also discussed and a personal viewpoint about the potential directions for future research is given.

A Multi‐Scale Approach for Modeling the Optical Response of Molecular Materials Inside Cavities

“…The material parameters of the medium are the effective permittivity eff ε , the effective permeability eff µ , and the effective chirality parameter eff κ . For the periodic system of the SURMOF, the values of eff ε and eff µ are obtained from the central object in Equation ( 4) (19) which we call eff T , for "effective T-matrix in the lattice". As explained in ref.…”

“…degree of freedom amenable to optimization beyond Fabry-Perot configurations, [6][7][8] and, when the interaction is strong enough, hybrid light-matter modes known as polaritons will form inside the cavity: The optical properties of the joint system can differ significantly from the separate responses of cavity and materials. [10][11][12][13][14][15][16][17][18][19] The choice of MOFs as active materials inside the cavities is motivated by the crystallinity and porosity of this class of reticular compounds, which makes possible a straightforward experimental characterization using X-ray diffraction methods as well as a tuning of the dielectric constant inside the cavity by loading the MOFs with small molecules. Hybrid light-matter states have also been observed in MOFs placed on a plasmonic nanoparticle lattice [20] and even in molecular films on top of substrates.…”

Tuning the Coherent Propagation of Organic Exciton‐Polaritons through Dark State Delocalization

“…trapped inside an optical resonator is governed by three key rates: the rate at which light and matter transfer energy (g), the rate at which light escapes the cavity (𝜅) and the rate and charge carrier transport, [17][18][19][20] and alterations to molecular photophysics from isomerization to spin interconversion. [21][22][23][24] These advantages persist in devices, where they permit efficient emission or enhanced light-harvesting. [8,[25][26][27] One of the most promising polaritonic properties that may be utilized in optoelectronic devices is their large energy transfer or propagation length, which ranges from 100's of nm to 10's of μm depending on cavity architecture.…”

“…In addition to exhibiting Bose–Einstein condensation, lasing and superfluidity, [ 12 , 13 , 14 , 15 , 16 ] organic polaritons have been reported to result in significant changes to bulk material properties from work function to energy and charge carrier transport, [ 17 , 18 , 19 , 20 ] and alterations to molecular photophysics from isomerization to spin interconversion. [ 21 , 22 , 23 , 24 ] These advantages persist in devices, where they permit efficient emission or enhanced light‐harvesting. [ 8 , 25 , 26 , 27 ] One of the most promising polaritonic properties that may be utilized in optoelectronic devices is their large energy transfer or propagation length, which ranges from 100's of nm to 10's of µm depending on cavity architecture.…”

Polariton condensation in a microcavity using a highly-stable molecular dye

“…16 For a recent review on polariton condensation in organic microcavities, see ref. 17. For practical applications, it is desirable that such molecules have a high degree of photostability.…”