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We report three yellow-green to yellow TADF dopants 26DAcBPy, 25DAcBPy and 26DPXZBPy containing dibenzoyl pyridine as the acceptor and dimethylacridine (Ac) and phenoxazine (PXZ) as the donors with short delayed fluorescence lifetimes of 2.3 μs, 1.9 μs, and 1.0 μs, respectively. The crystal structures show that 26DAcBPy and 26DPXZBPy have a U shape conformation and 25DAcBPy a linear chain structure. All three molecules show intramolecular hydrogen bonding between the pyridine nitrogen and the o-hydrogen of a phenyl ring. These conformations appear to be the result of hydrogen bonding, which leads to rigid structures and provides higher photoluminescence quantum yield. Lastly, these molecules show large dihedral angles between the donor group and the spacer phenyl unit leading to a well-separated HOMO and LUMO and small ΔEST values. Combined with the small ΔEST values, and good photoluminescence (PL) quantum yields, the 26DAcBPy-based devices show a maximum efficiency of 23.1% with a mild efficiency roll-off.

Thermally activated delayed fluorescence (TADF) emitters are attractive for display and lighting applications. Here, a series of highly efficient blue TADF emitters including 3,5-bis((3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)(pyridin-4-yl)methanone (4BPy-mDTC), (3,5-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)(pyridin-3-yl)methanone (3BPy-mDTC), (3,5-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)(pyridin-2-yl)methanone (2BPy-mDTC) and (3,5-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)(phenyl)methanone (BP-mDTC) were designed and synthesized. The molecular structures feature two meta carbazole substituents attached to a benzoylpyridine (BPy) group or to a benzophenone (BP) group. These compounds show high thermal stability (Td = 371–439 °C), blue emissions (458–488 nm), high photoluminescence quantum yields (PLQY) (75–96%) in thin films and very small energy gaps between S1 and T1 (ΔEST) of 0.01–0.05 eV. In addition, they all reveal TADF properties including small ΔEST, two components in the transient PL decays, prompt emission and temperature-dependent delayed emission. The BPy series appears to give much higher photoluminescence quantum yields (PLQY > 92%) than BP-mDTC (75%) plausibly due to the more rigid structure caused by the interaction between pyridine nitrogen and the aromatic C–H bond. Furthermore, 4BPy-mDTC shows a more delayed component compared to 3BPy-mDTC and 2BPy-mDTC. The electroluminescent devices based on 4BPy-mDTC and 2BPy-mDTC as the dopant emitters exhibit sky blue emission with maximum external quantum efficiencies (EQEs) over 28%, and current and power efficiency and maximum luminance up to 67.0 cd A−1, 60.1 lm W−1 and 20 000 cd m−2, respectively. The presence of the pyridine ring and the position of the nitrogen atom in the molecules are critical for the high quantum yield and device efficiency. The PLQY EQE and luminance are dramatically improved by changing the phenyl into a pyridine group in the dopant in these devices.

A thermally activated delayed fluorescent (TADF) material containing two meta carbazolyl groups on the phenyl ring of the benzoyl-4-pyridine moiety was prepared and its luminescence showed a colour change from blue to green by external stimuli. The organic-blue-light-emitting device using this TADF dopant provided a high external quantum efficiency of 18.4%.

A series of tetradentate Schiff base metallomesogenic diols and their model compounds were synthesized from two simple dihydroxy benzenes. The metallomesogenic diol was constructed from three ring containing mesogen linked through ester and azomethine with terminal hydroxy group. This upon complexation with copper(II) formed metallomesogenic diol with varing terminal chain length. The related model metallomesogenic compounds were also synthesized with varying chain length with terminal methyl group and compared the properties with metallomesogenic diols. Extensive characterization of all metallomesogenic compounds and intermediates were carried out by FT-IR, 1 H & 13 C NMR, EPR, VSM, Mass (EI and FAB) and UV–Vis spectroscopy. Hot stage polarizing microscope, Differential scanning calorimetry was used to ensure the phase characteristics such as nature of phase, melting and clearing temperatures and phase range. The appearance of enantiotropic smectic A phases indicated high molecular polarizability of the core due to the metal ion. The role of copper(II) ion on mesogens were discussed.

In this study, polymeric nanocomposites of poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) and functionalized multi-walled carbon nanotubes (MWCNTs) were spin coated on a pre-patterned ITO glass and used as a hole conducting layer in organic photovoltaic cells. The multi-layered ITO/MWCNT-PEDOT:PSS/CuPc/C60/Al devices were fabricated to investigate the current density-voltage characteristics and power conversion efficiency. The power conversion efficiency obtained from the device with a concentration of 1.0 wt% MWCNT in the PEDOT:PSS layer was increased twice as those adopted from device without MWCNT doping in the PEDOT:PSS layer and current density-voltage characteristics was also improved well with incorporation of MWCNTs.

An efficient synthesis of highly substituted isoquinolinium salts from ketimines and alkynes via a Rh(iii)-catalyzed C–H bond activation and annulation reaction is described.

A series of divalent metal (Co 2+ , Ni 2+ , Cu 2+ )-incorporated tetradentate Schiff base complexes of the generic name 1,2-bis[(4-(2-hydroxy)ethoxy-2-hydroxyphenyl}methyl ketimino]ethane-metal(II) (BHEHPMKE-M)-metal-containing dihydroxy monomers-were synthesized and characterized by UV-visible, FT-IR, MS, and atomic absorption spectroscopies and elemental analysis. Structure of one of the monomers was also confirmed by single-crystal X-ray diffraction technique. Several metal-containing polyurethanes were prepared using these dihydroxy compounds and 1,4-butanediol as chain extenders for prepolymers based on poly(oxytetramethylene) glycol-2000 (PTMG-2000) and 4,4'-methylene bis(phenyl isocyanate) (MDI). The amount of metal-containing monomer was varied from 0 to 1 equivalent to find the influence of the metal-incorporated tetradentate Schiff base segment on thermal and mechanical properties of polyurethanes. The properties of metal-containing polyurethanes were compared with those prepared using 1,4-butanediol and 1,2-bis[{4-(2-hydroxy)ethoxy phenyl}-methyl ketimino]ethane-a diol without metal-as chain extenders. The polymers were characterized by FT-IR, GPC, DSC, TGA, viscosity, and solubility measurements. The glass transition temperature (T g ) of the polyurethane prepared from the Schiff base diol (without metal) was found to increase when used alone as chain extender. Thermal and mechanical properties of polyurethanes were also found to improve markedly by the introduction of metal-incorporated tetradentate Schiff base moiety into the polymer chain. The viscosity of the metal-containing polyurethane decreased abruptly upon increasing the metal content.