Exciton-polaritons are bosonic quasiparticles that arise from the normal mode splitting of photons in a microcavity and excitons in a semiconductor material. One of the most intriguing extensions of such a light−matter interaction is the socalled ultrastrong coupling regime. It is achieved when the Rabi frequency (Ω R , the energy exchange rate between the emitter and the resonant photonic mode) reaches a considerable fraction of the emitter transition frequency, ω 0 . Here, we report a Rabi energy splitting (2ℏΩ R ) of 1.12 eV and record values of the coupling ratio (2Ω R /ω 0 ) up to 0.6-fold the material band gap in organic semiconductor microcavities and up to 0.5-fold in monolithic heterostructure organic light-emitting diodes working at room temperature. Furthermore, we show that with such a large coupling strength it is possible to undress the exciton homogeneous linewidth from its inhomogeneous broadening, which allows for an unprecedented narrow emission line (below the cavity finesse) for such organic LEDs. The latter can be exploited for the realization of novel monochromatic sources and near-IR organic emitting devices.

The strong coupling of an excitonic transition with an electromagnetic mode results in composite quasi-particles called exciton polaritons, which have been shown to combine the best properties of their individual components in semiconductor microcavities. However, the physics and applications of polariton flows in organic materials and at room temperature are still unexplored because of the poor photon confinement in such structures. Here, we demonstrate that polaritons formed by the hybridization of organic excitons with a Bloch surface wave are able to propagate for hundreds of microns showing remarkable third-order nonlinear interactions upon high injection density. These findings pave the way for the study of organic nonlinear light–matter fluxes and for a technologically promising route of the realization of dissipation-less on-chip polariton devices operating at room temperature.

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A convergent strategy for the synthesis of three generations of dendrons comprised of carbazole moieties is described. The procedure to build the dendrons involves an iterative palladium catalysed amination-debenzylation sequence using N-benzyl-3,6-dibromocarbazole. The three carbazolyl focussed dendrons are then attached to a reactive fac-tris[2-phenylpyridyl]iridium(III) core by a palladium catalysed amination to give the dendrimers. The three generations of dendrons have one, three, and seven carbazole units leading to dendrimers with fac-tris[2-phenylpyridyl]iridium(III) cores and three, nine and twenty one carbazole units. The use of 9,9 0 -dialkylfluorenyl surface groups gave the dendrimers excellent solubility. The attachment of the carbazolyl-based dendrons did not change the emission colour significantly with the dendrimers emitting green phosphorescence. The dendrimers were highly luminescent with solution photoluminescence quantum yields of the order of 70%. Ground state molecular orbital calculations showed that while the ''LUMO'' was concentrated on the core iridium(III) complex the ''HOMO'' was delocalised across the core and each of the dendrons. This was reflected in the oxidation properties of the dendrimers whereby the increased carbazolyl character of the ''HOMO'' resulted in the first oxidation being moved to more positive potentials. Results and discussion SynthesisWhen developing the strategies for the preparation of dendrimers we have focussed on minimising the reaction types and steps for the formation of the different generations of

Here, the charge transporting properties of a family of highly phosphorescent iridium(III) complex‐cored carbazole dendrimers designed to have improved charge transport by incorporating carbazole units into the dendrons are studied. Firstly, the effect of the dendrimer generation and the role of dendron for materials with one dendron per ligand of the core are considered. It is shown, in contrast to previously reported light‐emitting dendrimers, that in this case the carbazolyl‐based dendrons have an active role in charge transport. Next, the effect on the charge transport of attaching two dendrons per ligand to the dendrimer core is explored. In this latter case, for the so called “double dendron” material a highly non‐dispersive charge transport behavior is observed, together with a time‐of‐flight mobility of the order of 10−3 cm2 V−1 s−1. Furthermore the lowest energetic disorder parameter (σ) ever reported for a solution‐processed conjugated organic material is found, σ <  20 meV.

Exciton-polaritons in semiconductors are quasi-particles which have recently shown the capability to undergo phase transition into a coherent hybrid state of light and matter. The observation of such quasi-particles in organic microcavities has attracted increasing attention for their characteristic of reaching condensation at room temperature. In this work we demonstrate that the emission properties of organic polaritons do not depend on the overlap between the absorption and emission states of the molecule and that the emission dynamics are modified in the strong coupling regime, showing a significant enhancement of the photoluminescence intensity as compared to the bare dye. This paves the way to the investigation of molecules with large absorption coefficients but poor emission efficiencies for the realization of polariton condensates and organic electrically injected lasers by exploiting strong exciton-photon coupling regimes.2

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An increase in yield from below 50 up to 90% is realized on using sacrificial anodes in the electrochemical carboxylation of organic halides. The metal ion liberated from the anodes reacts with the cathodically formed carboxylate to give isolable salts and thus prevents undesired esterification.