4-NR2-appended salen–indium complexes were prepared via a one-pot synthetic pathway. The complexes exhibited narrow-bandwidth red emissions with high photoluminescence quantum yields that are the highest among the reported salen-based luminophores.
A series of planarized B,N‐diarylated dibenzoazaborine compounds (5a–5e) in which various functional groups are introduced into the B‐Ph and N‐Ph moieties of nonsubstituted dibenzoazaborine compound (I) were prepared. All compounds exhibit strong low‐energy absorptions at ca. 410–426 nm with a gradual red‐shift depending on the electron‐accepting property of the four substituents (4‐R = 4‐Ph < 4‐Pm < 4‐CNPh <4‐CN) on the B‐Ph ring in 5a–5d. Introduction of an electron‐donating tBu group into the N‐Ph ring further shifts slightly the absorption band toward a lower‐energy region (5e). Importantly, all compounds undergo gradual red‐shifts in the emission leading to deep blue fluorescence for CN‐substituted 5d and 5e. Furthermore, the emissions have narrow full width at half maximum values of ca. 30 nm, high photoluminescence quantum yields (ΦPL ≈ 100%), and small Stokes shifts (11–16 nm). The electrochemical and theoretical studies further support the bandgap control and photophysical properties of compounds.
Designing multi‐resonance (MR) emitters that can simultaneously achieve narrowband emission and suppressed intermolecular interactions is challenging for realizing high color purity and stable blue organic light‐emitting diodes (OLEDs). Herein, a sterically shielded yet extremely rigid emitter based on a triptycene‐fused B,N core (Tp‐DABNA) is proposed to address the issue. Tp‐DABNA exhibits intense deep blue emissions with a narrow full width at half maximum (FWHM) and a high horizontal transition dipole ratio, superior to the well‐known bulky emitter, t‐DABNA. The rigid MR skeleton of Tp‐DABNA suppresses structural relaxation in the excited state, with reduced contributions from the medium‐ and high‐frequency vibrational modes to spectral broadening. The hyperfluorescence (HF) film composed of a sensitizer and Tp‐DABNA shows reduced Dexter energy transfer compared to those of t‐DABNA and DABNA‐1. Notably, deep blue TADF‐OLEDs with the Tp‐DABNA emitter display higher external quantum efficiencies (EQEmax=24.8 %) and narrower FWHMs (≤26 nm) than t‐DABNA‐based OLEDs (EQEmax=19.8 %). The HF‐OLEDs based on the Tp‐DABNA emitter further demonstrate improved performance with an EQEmax of 28.7 % and mitigated efficiency roll‐offs.
Deep-red (DR)-to-near-infrared (NIR) phosphorescent organic light-emitting diodes (OLEDs) have potentials for application in various fields ranging from phototherapy to sensing. Accordingly, herein, phenylpyridazinebased bidentate ligands are synthesized and subsequently utilized for the preparation of dinuclear Pt(II) complexes (1-6). The molecular structures of 1-3 is investigated by single-crystal X-ray diffraction, and the results suggest that these complexes have substantially shortened Pt•••Pt distances (2.906-2.911 Å). Complexes 1-6 exhibit intense emissions in the NIR region (700-726 nm), high photoluminescence quantum yield (PLQY) (0.11-0.18), and short phosphorescence decay lifetimes (τ = 0.64-0.95 µs) in a CH 2 Cl 2 solution. To examine the effect of N-substitution on the dinuclear Pt complexes, the phenylpyrimidine-based Pt(II) emitters 7 and 8 are prepared and discovered to have Pt•••Pt distances of 2.933 Å. 7 and 8 demonstrate strong emissions in the 628-650 nm range with high PLQY of 0.52-0.65. Theoretical studies indicate that the functional groups or atoms in the ligands play crucial roles in the formation of emitters with significantly shortened Pt•••Pt distances. 3 and 7 are employed as non-doped emitters to fabricate NIR OLEDs, and the resulting OLEDs exhibit electroluminescence peaks at 754 and 692 nm with maximum external quantum efficiencies of 3.0 and 4.4%, respectively.
We report the impact of boron acceptors on the thermally activated delayed fluorescence (TADF) properties of ortho -donor-appended triarylboron compounds. Different boryl acceptor moieties, such as 9-boraanthryl ( 1 ), 10 H -phenoxaboryl ( 2 ), and dimesitylboryl (BMes 2 , 3 ) groups have been introduced into an ortho donor (D)–acceptor (A) backbone structure containing a 9,9-diphenylacridine (DPAC) donor. X-ray crystal diffraction and NMR spectroscopy evidence the presence of steric congestion around the boron atom along with a highly twisted D–A structure. A short contact of 2.906 Å between the N and B atoms, which is indicative of an N → B nonbonding electronic interaction, is observed in the crystal structure of 2 . All compounds are highly emissive (PLQYs = 90–99%) and display strong TADF properties in both solution and solid state. The fluorescence bands of cyclic boryl-containing 1 and 2 are substantially blue-shifted compared to that of BMes 2 -containing 3 . In particular, the PL emission bandwidths of 1 and 2 are narrower than that of 3 . High-efficiency TADF-OLEDs are realized using 1 – 3 as emitters. Among them, the devices based on the cyclic boryl emitters exhibit pure blue electroluminescence (EL) and narrower EL bands than the device with 3 . Furthermore, the device fabricated with emitter 1 achieves a high external quantum efficiency of 25.8%.
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