This work describes a strategy to produce circularly polarized thermally activated delayed fluorescence (CP-TADF). A set of two structurally similar organic emitters SFST and SFOT are constructed, whose spiro architectures containing asymmetric donors result in chirality. Upon grafting within the spiro frameworks, the donor and acceptor are fixed proximally in a face-to-face manner. This orientation allows intramolecular through-space charge transfer (TSCT) to occur in both emitters, leading to TADF properties. The donor units in SFST and SFOT have a sulfur and oxygen atom, respectively; such a subtle difference has great impacts on their photophysical, chiroptical, and electroluminescence (EL) properties. SFOT exhibits greatly enhanced EL performance in doped organic light-emitting diodes, with external quantum efficiency (EQE) up to 23.1%, owing to the concurrent manipulation of highly photoluminescent quantum efficiency (PLQY, ∼90%) and high exciton utilization. As a comparison, the relatively larger sulfur atom in SFST introduces heavy atom effects and leads to distortion of the molecular backbone that lengthens the donor–acceptor distance. SFST thus has lower PLQY and faster nonradiative decay rate. The collective consequence is that the EQE value of SFST, i.e., 12.5%, is much lower than that of SFOT. The chirality of these two spiro emitters results in circularly polarized luminescence. Because SFST has a more distorted molecular architecture than SFOT, the luminescence dissymmetry factor (|g lum|) of circularly polarized luminescence of one enantiomer of the former, namely, either (S)-SFST or (R)-SFST, is almost twice that of (S)-SFOT/(R)-SFOT. Moreover, the CP organic light-emitting diodes (CP-OLEDs) show obvious circularly polarized electroluminescence (CPEL) signals with g EL of 1.30 × 10–3 and 1.0 × 10–3 for (S)-SFST and (S)-SFOT, respectively.

No abstract

basically limited to donor (D)-π-acceptor (A) molecular architecture. [2] This type of molecular design, first proposed by Adachi and co-workers for TADF, [1a] can tune their D or/and A groups, geometries, and steric hindrance between them to generate twisted induced charge-transfer-type emission. [3] The twisted dihedral angle between D and A units can minimize the singlettriplet splitting energy (ΔE ST) for fast RISC, [1c,4] but the resulted TADF OLEDs still need to be significantly improved, notably in terms of efficiency roll-off at high brightness and concentration quenching because of the ππ intermolecular interactions in the solid-state. [5] Another way to achieve TADF is to use D/A complex, in which the D/A blocks are spatially isolated, but their forming exciplexes are far less efficient than D-π-A analogs, and the resulting OLEDs also display severe efficiency roll-off. [6] Recently, researchers conceptually consider that the intramolecular noncovalent interaction between D/A units in faceto-face alignment could be a new option to realize TADF. [7] Constructing TADF materials in this unconjugated way has the potential to combine the small ΔE ST value with substantial transition dipole and achieve high luminescent efficiency. [8] These two electron-rich and electron-poor π-systems need to be held close in space to form homoconjugation. In this regard, The ORCID identification number(s) for the author(s) of this article can be found under

Derivatives based on anthryleno[1,2-b]pyrazine-2,3dicarbonitrile (DCPA) are used as luminescent materials,t o realizen ear-infrared (NIR) electroluminescence.Byf unctionalizing DCPAw ith aromatic amine donors,t wo emitters named DCPA-TPAa nd DCPA-BBPAa re designed and synthesized.Both molecules have large dipole moments owing to the strong intramolecular charge transfer interactions between the amine donors and the DCPAa cceptor.T hus, compared with doped films,t he emission of neat films of DCPA-TPAa nd DCPA-BBPAc an fully fall into the NIR region (> 700 nm) with increasing surrounding polarity by increasing doping ratio.M oreover,t he non-doped devices based on DCPA-TPAa nd DCPA-BBPAp rovideN IR emission with peaks at 838 and 916 nm, respectively.Amaximum radiance of 20707 mW Sr À1 m À2 was realized for the further optimizedd evice based on DCPA-TPA. This work provides as imple and efficient strategy of molecular design for developing NIR emitting materials.

A novel donor (D)–spiro-acceptor (A) emitter, namely 10-phenyl-10H-spiro[acridine-9,9′-fluorene]-2′,4′,7′-tricarbonitrile (SAF-3CN), was synthesized for high efficiency, yellowish green third-generation thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs).