Polypeptides have broad applications and can be prepared via ring-opening polymerization of α-amino acid N-carboxyanhydrides (NCAs). Conventional initiators, such as primary amines, give slow NCA polymerization, which requires multiple days to reach completion and can result in substantial side reactions, especially for very reactive NCAs. Moreover, current NCA polymerizations are very sensitive to moisture and must typically be conducted in a glove box. Here we show that lithium hexamethyldisilazide (LiHMDS) initiates an extremely rapid NCA polymerization process that is completed within minutes or hours and can be conducted in an open vessel. Polypeptides with variable chain length (DP = 20–1294) and narrow molecular weight distribution (Mw/Mn = 1.08–1.28) were readily prepared with this approach. Mechanistic studies support an anionic ring opening polymerization mechanism. This living NCA polymerization method allowed rapid synthesis of polypeptide libraries for high-throughput functional screening.

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A series of ultrapure-blue thermally activated delayed fluorescence (TADF) emitters featuring through-space charge transfer (TSCT) have been constructed by close stacking between the donor and acceptor moieties in rigid heteroaromatic compounds. The obviously accelerated radiative transition of singlet excitons, the diminished vibrionic relaxation of ground and excited states, and the consequent reduced Stokes shift and the narrow emission are evident. The corresponding organic light-emitting diodes (OLEDs) based on AC-BO realize the best performance among all deep-blue TSCT-TADF emitters, with an external quantum efficiency (EQE max ) of 19.3 %. Furthermore, the OLEDs based on QAC-BO display an EQE max of 15.8 %, and achieve the first high-efficiency ultrapureblue TSCT-TADF material with an excellent Commission Internationale de L'Eclairage coordinate (CIE) of (0.145, 0.076) which perfectly matches the ultrapureblue CIE requirements (0.14, 0.08) defined by the National Television System Committee.

The state-of-the-art luminescent materials are gained widely by utilizing thermally activated delayed fluorescence (TADF) mechanism. However, the feasible molecular designing strategy of fully exploiting triplet excitons to enhance TADF properties is still in demand. Herein, TADF emitters with multiple conversion channels of triplet excitons are designed by concisely halogenating the electron acceptors containing carbonyl moiety. Compared with the chlorinated and brominated analogues, the fluorinated emitter exhibits distinguishing molecular stacking structures, participating in the formation of trimers through integrating C-H•••F and C═O•••H hydrogen bonds together. It is also demonstrated that the multiple channels can be involved synergistically to accelerate the spin-flip of triplet excitons, and to take charge of the relatively superior reverse intersystem crossing constant rate of 6.20 × 10 5 s -1 , and thus excellent photoluminescence quantum yields over 90% can easily be achieved. Then the solution-processable organic light emitting diode based on fluorinated emitter can achieve a record-high external quantum efficiency value of 27.13% and relatively low efficiency roll-off with remaining 24.74% at 1000 cd m −2 . This result manifests the significance of enhancing photophysical properties through constructing multiple conversion channels of triplets excitons for high-efficiency TADF emitters and provides a guideline for the future study.

Thermally activated delayed fluorescence (TADF) conjugated polymers are attractive for display and illumination applications owing to their excellent device performance and convenient device fabrication. However, conjugated polymers frequently encounter insufficient energy transfer from hosts to TADF units, lowering device performance. Herein, a strategy for improving light-emitting performances through adjusting the local electronegativity of the polymeric backbones by inserting electron-withdrawing atoms and activating energy transmission channels is proposed. Meanwhile, strongly electronegative atoms also affect the charge-transfer natures (CT) of TADF polymers and minimize the energy difference between the lowest singlet and triplet states, leading to a rapid reverse intersystem crossing process through the vibronic coupling between 1 CT and 3 CT with extremely close energy levels. The produced TADF polymer, pBP-PXZ, can achieve an external quantum efficiency (EQE) of 23.11%, exhibiting no roll-off when the luminance is less than 200 cd m −2 whereas only a 3% EQE decrease at 500 cd m −2 . The EQE can even maintain above 19% under 1000 cd m −2 , which is the highest efficiency among TADF polymer-based organic light-emitting diodes (OLEDs) under high luminance. The study provides a new perspective for designing highperformance OLEDs materials.