Embrace the darkness: An experimental perspective on organic exciton–polaritons

Abstract

Organic polaritonics has emerged as a captivating interdisciplinary field that marries the complexities of organic photophysics with the fundamental principles of quantum optics. By harnessing strong light–matter coupling in organic materials, exciton–polaritons offer unique opportunities for advanced device performance, including enhanced energy transport and low-threshold lasing, as well as new functionalities like polariton chemistry. In this review, we delve into the foundational principles of exciton–polaritons from an experimental perspective, highlighting the key states, processes, and timescales that govern polariton phenomena. Our review centers on the spectroscopy of exciton–polaritons. We overview the primary spectroscopic approaches that reveal polariton phenomena, and we discuss the challenges in disentangling polaritonic signatures from spectral artifacts. We discuss how organic materials, due to their complex photophysics and disordered nature, not only present challenges to the conventional polariton models but also provide opportunities for new physics, like manipulating dark electronic states. As the research field continues to grow, with increasingly complex materials and devices, this review serves as a valuable introductory guide for researchers navigating the intricate landscape of organic polaritonics.

Study of the Selection Rules of Molecular Polaritonic Transitions by Two-Photon Absorption Spectroscopy

“…This results from the transient change of the dielectric constant of the cavity mirror. The obtained response time in our case is close to the laser-induced ultrafast decay time of the thin silver film (∼1 ps) , and agrees with the ultrafast heating of electrons in the metal cavity mirror. − However, the time response of the pure cavity resonance is shorter than that for the transient spectra of the strongly coupled TDBC under 2PA, considering that the 0-delay spectra of the ESC cavity under 2PA excitation have different features around polariton peak compared with that of the pure cavity. This indicates a polariton-related excited state dominates the transient spectra in ESC cavity under 2PA excitation.…”

Radiative pumping in a strongly coupled microcavity filled with a neat molecular film showing excimer emission

“…27–29 The radiative pumping mechanism is explained by incoherent emission from the intracavity dark state that populates the LP state, resulting in similar decay profiles to the active layer. 30–34 Interestingly, in the presence of electronic coupling between an excited singlet state and a triplet pair state, the delayed PL, originally from triplet–triplet annihilation, has been found to be altered under strong coupling. 24 Further studies from nanosecond to microsecond timescales are necessary to unveil the population dynamics of exciton–polaritons.…”

Molecular strong coupling: evaluating dipole oscillator and cavity field parameters

“…With N molecular resonators coupled to the same cavity mode, the strength of the interaction is scaled up by N [11]. It is this scaling with N that can lead to the coupling being sufficient for two new hybrid modes (polaritons) to emerge, the original molecular resonance and cavity mode losing their separate identity [3,4,12]. To make contact with the literature it is convenient to write the interaction energy for N molecules in a cavity as ÿΩ R , where Ω R is known as the Rabi frequency [13].…”