With 5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene (OBA) as the acceptor, thermally activated delayed fluorescence (TADF) emitters adopting an asymmetric configuration can achieve highly efficient blue-emitting OLEDs.

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Three Ir­(C∧N)2(acac)-type and one Ir­(C1 ∧N)­(C2 ∧N)­(acac)-type coumarin-based cyclometalated Ir­(III) complex isomers (IrC5, IrC7, IrC7-A, and IrC8) have been obtained using three coumarin-based isomers of 2-phenylpyridine (ppy)-type cyclometalating ligands (L-C5, L-C7, and L-C8). Two coordination isomers emerging as principal products (IrC7 and IrC7-A) are obtained in the synthesis of corresponding coumarin-based cyclometalated Ir­(III) complexes because of two different coordination sites in ligand L-C7 to form a C–Ir bond. To the best of our knowledge, there are no such isomers reported to date. Interestingly, a broad range of phosphorescent color tuning from green (IrC8, λ = 516 nm) to red (IrC5, λ = 608 nm) has been realized through variation of the pyridyl substitution positions on the fused phenyl ring of the coumarin skeleton. In addition, based on natural transition orbital (NTO) analyses, features of the lowest triplet excited states (T1) from these coumarin-based cyclometalated Ir­(III) complex isomers can be tuned easily by these ligand isomers as well. IrC5, IrC7, and IrC7-A show prevailing 3MLCT character associated with their T1 states which emit the phosphorescent signals, while the T1 state of IrC8 exhibits the dominant ligand-centered π–π* transition feature. Importantly, owing to the strong rigidity of the coumarin skeleton, all the coumarin-based cyclometalated Ir­(III) complex isomers can show high phosphorescent quantum yields Φp (ca. 0.4–1). Together with the improved electron-injection/electron-transport (EI/ET) ability, all the phosphorescent emitters display impressive electroluminescence (EL) performance. The device based on IrC8 gives the highest EL efficiencies of external quantum efficiency (ηext) 22.7%, current efficiency (ηL) 79.7 cd A–1, and power efficiency (ηP) 58.2 lm W–1, representing the most state-of-the-art EL ability ever achieved by coumarin-based phosphorescent emitters. All these encouraging data definitely suggest the great potential of the coumarin skeleton in both easy tuning of the photophysical properties of ppy-type Ir­(III) phosphorescent complexes and developing high-performance phosphorescent emitters.

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Waterborne coating has recently been paid much attention. However, it cannot be used widely due to its performance limitations. Under the specified conditions of the selected resin, selecting the function pigment is key to improving the anticorrosive properties of the coating. Zinc phosphate is an environmentally protective and efficient anticorrosion pigment. In this work, zinc phosphate was used in modifying waterborne acrylic coatings. Moreover, the disbonding resistance of the coating was studied. Results showed that adding zinc phosphate can effectively inhibit the anode process of metal corrosion and enhance the wet adhesion of the coating, and consequently prevent the horizontal diffusion of the corrosive medium into the coating/metal interface and slow down the disbonding of the coating.

With the 9-phenyl-9-phosphafluorene oxide (PhFlOP) moiety as the acceptor (A) and various donors (D), a series of new organic emitters have been synthesized with a D–A–D configuration. Their photophysical and electrochemical behaviors and electroluminescent (EL) performances have been characterized in detail. The photophysical results have indicated that the PhFlOP-based emitters with acridyl, phenoxazyl, and phenothiazyl as donors show efficient, thermally activated delayed fluorescence (TADF) behavior, especially for the TADF emitter with the phenoxazyl donor possessing an exceptionally high rate constant of reverse intersystem crossing (k RISC) of 6.2 × 105 s–1. It has also been found that their TADF behavior can be greatly affected by the substitution position of the donors. Different from the reported aryl phosphine oxide (APO) acceptors in TADF emitters, the PhFlOP moiety adopts a highly rigid configuration to guarantee a photoluminescent quantum yield as high as 0.80 in the 4,4′-N,N′-dicarbazolebiphenyl film, representing the top-ranking emission ability for the TADF emitters with APO-type acceptors. Benefitting from their advanced TADF performances, the doped organic light-emitting diodes/devices based on these PhFlOP-based TADF emitters can achieve exceptional EL performances with the maximum external quantum efficiency (ηext) of 23.3%, current efficiency (ηL) of 83.7 cd A–1, and power efficiency (ηP) of 59.1 lm W–1. These encouraging EL data show the great potential of the PhFlOP moiety in developing highly efficient TADF emitters.

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