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Organic light-emitting diodes (OLEDs) that are able to emit high levels of circularly polarized (CP) light hold significant promise in numerous future technologies. Such devices require chiral emissive materials to enable CP electroluminescence. However, the vast majority of current OLED emitter classes, including the state-of-the-art triplet-harvesting thermally activated delayed fluorescence (TADF) materials, produce very low levels of CP electroluminescence. Here a host-guest strategy that allows for energy transfer between a chiral polymer host and a representative chiral TADF emitter is showcased. Such a mechanism results in a large amplification of the circular polarization of the emitter. As such, this study presents a promising avenue to further boost the performance of circularly polarized organic light-emitting diode devices, enabling their further development and eventual commercialization., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

Cyanine dyes are known to form H - and J -aggregates in aqueous solutions. Here we show that the cyanine dye, S0271, assembles in water into vortex induced chiral J -aggregates. The chirality of the J -aggregates depends on the directionality of the vortex. This study utilised both conventional benchtop CD spectropolarimeters and Mueller matrix polarimetry. It was found that J -aggregates have real chirality alongside linear dichroism and linear and circular birefringence. We identify the factors that are key to the formation of metastable chiral J -aggregates and propose a mechanism for their assembly.

Solid-state ECD (ss-ECD) spectra of a model microcrystalline solid, finasteride, dispersed into a KCl pellet were recorded by using the synchrotron radiation source at the Diamond B23 beamline. Scanning a surface of 36 mm 2 with a step of 0.5 mm, we measured a set of ECD imaging (ECDi) spectra very different from each other and from the ss-ECD recorded with a bench-top instrument (1 cm 2 area). This is due to the anisotropic part of the ECD (ACD), which averages to zero in solution or on a large number of randomly oriented crystallites, but can otherwise be extremely large. Two-way singular value decomposition (SVD) analysis, through experimental and simulated TDDFT spectra, disclosed that the measured and theoretical principal components are in line with each other. This finding demonstrates that the observed isotropic ss-ECD spectrum is governed by the anisotropy of locally oriented crystals. It also introduces a new quality for ss-ECD measurements and opens a new future for probing and mapping chiral materials in the solid state such as active pharmaceutical ingredients (APIs)., (© 2021 Wiley-VCH GmbH.)