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Thermally activated delayed fluorescence (TADF) has been explored actively in luminescent organic materials. Yet, realizing such TADF-active, multifunctional emitters with high emission efficiency still remains hugely challenging. In this context, a series of twist-conjugated organic molecules bearing diphenylsulfone and 9,9-dimethylacridine moieties are designed and prepared, and are found to show, in one molecule, TADF, room-temperature phosphorescence, triboluminescence, and aggregation-induced emission enhancement. In addition, remarkably high photoluminescence quantum efficiency, up to ≈100%, is achieved for these novel molecules. Single-crystal analysis and theoretical calculations reveal that the through-space charge transfer (TSCT) effect in these molecules is responsible for both the multifunctional emission and high emission efficiency. A maximum external quantum efficiency of 20.1% is achieved, which is among the highest recorded in a solution-processable device containing TSCT-based TADF materials. These results illustrate a new approach to achieving highly efficient TADF-active, multifunctional emitters.

The gas-liquid interface of ionic liquids (ILs) is critically important in many applications, for example, in supported IL phase (SILP) catalysis. Methods to investigate the interfacial structure in these systems will allow their performance to be improved in a rational way. In this study, reactive-atom scattering (RAS), surface tension measurements, and molecular dynamics (MD) simulations were used to study the vacuum interface of mixtures of partially fluorinated and normal alkyl ILs. The underlying aim was to understand whether fluorinated IL ions could be used as additives to modify the surface structure of one of the most widely used families of alkyl ILs. The series of ILs 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Cnmim][Tf2N]) with n = 4-12 were mixed with a fixed-length, semiperfluorinated analogue (1H,1H,2H,2H-perfluorooctyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C8mimF13][Tf2N]), forming [Cnmim](1-x)[C8mimF13]x[Tf2N] mixtures, where x is the bulk mole fraction of the fluorinated component. The RAS-LIF method combined O-atom projectiles with laser-induced fluorescence (LIF) detection of the product OH as a measure of surface exposure of the alkyl chains. For [C8mim](1-x)[C8mimF13]x[Tf2N] mixtures, RAS-LIF OH yields are below those expected from stoichiometry. There are quantitatively consistent negative deviations from linearity of the surface tension. Both results imply that the lower-surface-tension fluoroalkyl material dominates the surface. A similar deficit is found for alkyl chain lengths n = 4, 6, 8, and 12 and for all (nonzero) x investigated by RAS-LIF. Accessible-surface-area (ASA) analyses of the MD simulations for [Cnmim](1-x)[C8mimF13]x[Tf2N] mixtures qualitatively reproduce the same primary effect of fluoro-chain predominance of the surface over most of the range of n. However, there are significant quantitative discrepancies between MD ASA predictions and experiment relating to the strength of any n-dependence of the relative alkyl coverage at fixed x, and on the x-dependence at fixed n. These discrepancies are discussed in the context of detailed examinations of the surface structures predicted in the MD simulations. Potential explanations, beyond experimental artifacts, include inadequacies in the classical force fields used in the MD simulations or the inability of simple ASA algorithms to capture dynamical factors that influence RAS-LIF yields.

By functionalising 2,5-di(N,N′-carbazolyl)terephthalonitrile or 2,3,5,6-tetra(N,N′-carbazolyl)terephthalonitrile with alkoxy chains located on the carbazole moiety, a family of materials is realised, all of which show a TADF response and two of which are also liquid crystalline. This journal is

Emissive gold(iii) complexes of pincer 2,6-diphenylpyridines also bearing a phenylacetylide ligand have been modified at both the pincer and phenylacetylide to confer liquid crystalline properties, with most complexes showing a columnar hexagonal phase in the condensed phase. Solution NMR studies show a preferred orientation for self-association, consistent with structural parameters in the liquid crystal phase obtained by X-ray methods. While the pattern of substitution of the phenylacetylide has no discernible effect on the photophysics, when two alkoxy chains are attached to the pincer ligands, photoluminescence quantum yields (PLQY) of around 3% are found, whereas when four alkoxy chains are attached the PLQY increases significantly to 36%. Insight from computational chemistry indicated that the incorporation of the alkoxy donor groups raises the energy of the pincer-based HOMO−1 orbital, with a concomitant lowering of the LUMO ← HOMO−1 transition energy, consistent with an experimentally observed red shift. The gold complexes were fabricated into OLED devices using solution processing methods, being doped into the emissive layer at 5%, leading to external quantum efficiencies of up to 7.14%, values that compare well with those of related complexes in the literature.

Circularly polarized luminescence (CPL) is of interest due to its wide potential application in semiconductors. To balance the emission efficiency and luminescence dissymmetry factor (gPL) of a CPL emitter, in this context, two chiral, phosphorescent and liquid-crystalline cyclometalated platinum complexes, abbreviated R-Pt and S-Pt, are prepared. The complexes, which show an intense green emission at 504 nm both in solution and in the solid state, contain a simple, ortho-metalated 2-phenylpyridine unit functionalized with a chiral 2-octanol chain, with liquid crystallinity being induced by modifying the β-diketonato ligand with mesogenic groups. Interestingly, both the chiral smectic (SmA*) and nematic (N*) phases are found by a combination of polarized optical microscopy, differential scanning calorimetry, and small-angle X-ray scattering. By annealing, distinct CPL emission is achieved in the solid state with a gPL around 0.02. Employing the chiral platinum complexes as the dopant, solution-processable organic light-emitting diodes present an external quantum efficiency of 11.3% and strong, circularly polarized electroluminescence with an extremely high luminescence dissymmetry value (gEL) of 0.06 after annealing at 100 °C. This work opens an avenue for designing CPL-active emitters with high emission efficiency and high dissymmetry factor.