Heterocoronene, a new redox-active core fragment, is utilized for the synthesis of room-temperature columnar discotic liquid crystals (DLCs). Three wedge-shaped side chains having different lengths of alkyl tails are introduced at the periphery of the heterocoronene core to prepare three kinds of discotic molecules, 1 (R = C 10 H 21 ), 2 (R = C 12 H 25 ), and 3 (R = C 14 H 29 ). X-ray diffraction (XRD) analysis confirmed the packing variation in the columnar lattices regulated by alkyl chains of discrete length and steric bulk. When used in space charge limited current devices, compound 1 exhibits a high hole mobility value of 8.84 cm 2 /V s at ambient temperature, whereas compounds 2 and 3 show efficient ambipolar charge transport behavior with maximum hole (μ h ) and electron (μ e ) mobilities of 0.70 and 3.59 cm 2 /V s, respectively, for compound 3. The mobility values (μ h = 8.84 cm 2 /V s for 1 and μ e = 3.59 cm 2 /V s for 3) are remarkable and the highest ever disclosed for any DLC-based organic semiconductor, promising to deliver a good balance between mobility and processability in devices. The grazing incidence small-and wide-angle X-ray scattering experiments are employed to quantify the extent of alignment in the film state, which correlates with the observed trend of mobility values.

Room-temperature phosphorescence (RTP) originating from higher-lying triplet excitons remains a rather rarely documented occurrence for purely organic molecular systems. Here, we report two naphthalenebased RTP luminophores whose phosphorescence emission is enabled by radiative decay of high-lying triplet excitons. In contrast, upon cooling the dominant phosphorescence originates from the lowest-lying triplet excited state, which is manifested by a red-shifted emission. Photophysical and theoretical studies reveal that the unusual RTP results from thermally activated excitonic coupling between different conformations of the compounds. Aggregation-regulated excitonic coupling is observed when increasing the doping concentration of the emitters in poly(methylmethacrylate) (PMMA). Further, the RTP quantum efficiency improves more than 80-fold in 1,3-bis(N-carbazolyl)benzene (mCP) compared to that in PMMA. This design principle offers important insight into triplet excited state dynamics and has been exploited in afterglowindicating temperature sensing.

A novel design of aggregation-induced emission (AIE) active columnar (Col) luminomesogens is reported, and they are demonstrated to act as highly efficient deep-blue emitters in organic light-emitting diodes (OLEDs). All derivatives exhibit Col liquid crystalline (LC) behavior at room temperature over a wide temperature range and desirable alignment properties, which is very important in using them as materials for organic electronic devices. These new AIE active luminomesogens were found to act as highly efficient emitters in OLEDs and unveiled a maximum external quantum efficiency of 4.0% for the first time in Col LCs with Commission International de l’E’clairage coordinates of (0.17, 0.07), which closely matches the National Television System Committee (NTSC) standard, corresponding to pure deep blue color. The detailed supramolecular assembly of the compounds has been characterized by modeling in the mesophase derived from small- and wide-angle X-ray scattering results.

Five new, star-shaped compounds containing a central oligo­(phenylenevinylene) core carrying six alkoxy chains were synthesized, and with varying alkyl chains the changes in their supramolecular assembly were explored by small and wide-angle X-ray scattering (SAXS/WAXS) studies. For the shortest peripheral alkoxy chain (3.1; R = 3,7-dimethyl octyl) lamellar stacking was favored, whereas with increasing the alkoxy chain length (3.2, 3.3, 3.4, and 3.5; n-C12H25, n-C14H29, n-C16H33, n-C18H35) columnar rectangular (Colr) assembly was observed. The compound with branched peripheral chains (3.1) with lamellar assembly did not exhibit organogelation, but four other compounds (3.2, 3.3, 3.4 and 3.5) showed the ability to gelate in nonpolar solvents at a lower concentration even in less than 1 wt % (qualifying it as a supergelator), possibly due to their existence in the Colr packing having strong π–π interactions. This occurrence is less observed, in comparison to previous reports where supergelation happened mostly via H-bonding interactions. The hierarchical self-assembly of gels was investigated using transmission electron microscopy, scanning electron microscopy, atomic force microscopy, and X-ray diffraction studies. Interestingly, Colr packing was retained even in the gel state also. Rheological measurements performed on the samples displayed mechanical robusticity of these gels. All the compounds showed blue luminescence in solution as well as in thin-film states. The electroluminescent properties of the compound 3.3 were examined as emissive layers in organic light emitting diodes (OLEDs). It was explored by fabricating in OLED devices either as a host or dopant-emitters in the 4,4′-bis­(N-carbazolyl)-1,1′-biphenyl host with different concentrations 1, 3, 5, and 7 wt %. The device fabricated with 1 wt % revealed the best electroluminescence performance with maximum luminescence, current efficiency, power efficiency, and external quantum efficiency.

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