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π-Stacked dendrimers consisting of cofacially aligned donors and acceptors are developed by introducing three dendritic teracridan donors with orthogonal configuration and three triazine acceptors in periphery of hexaphenylbenzene skeleton. The dendritic structure and orthogonal configuration of teracridan not only make their outer acridan segments approaching to acceptor in close distance, but also fix donor and acceptor in face-to-face alignment, leading to through-space charge transfer emission with thermally activated delayed fluorescence (TADF) effect. By regulating charge transfer strength via substituent effect of acceptor, emission color of the dendrimers can be tuned from blue to yellow/red region. Solution-processed two-color white organic light-emitting diodes (OLEDs) based on blue and yellow π-stacked donor-acceptor dendrimers exhibit the maximum external quantum efficiency of 20.6 % and maximum power efficiency of 58.9 lm W-1 , representing the state-of-the-art efficiency for all-TADF white OLEDs by solution process.

Polymer light-emitting diodes (PLEDs) based on thermally activated delayed fluorescence (TADF) emitters show great potential in developing high-efficiency solution-processed light-emitting devices ...

Through-space charge transfer polynorbornenes with fixed and controllable spatial alignment of donor and acceptor in edge-to-face/face-to-face stacking patterns are developed for achieving high-efficiency blue thermally activated delayed fluorescence (TADF). The alignment is realized by using the cis, exo-configuration of norbornene to confine donor and acceptor in close proximity, and utilizing orthogonal and dendritic structures of donors to provide either perpendicular or parallel stacking motif relative to acceptors. Compared to edge-to-face counterparts, polynorbornenes with face-to-face aligned donor and acceptor exhibit much larger oscillator strength and higher photoluminescence quantum yield. The resulting polymers exhibit deep blue (422 nm) to sky blue (482 nm) emission and TADF effect with reverse intersystem crossing rates of 0.4-5.9×106 s-1 , giving the maximum external quantum efficiency of 18.8 % for non-doped blue organic light-emitting diodes by solution process.

Single white light-emitting polymers (SWPs) represent a high-fidelity system for generating white light emission from polymers without phase separation compared to polymer blend systems. However, their device performance so far has been limited because of the unwanted hole scattering caused by an energy-level mismatch between emitters and hosts, and the large injection barrier at the polymer/anode interface. Here, we report novel poly(arylene phosphine oxide)-based all-phosphorescent SWPs by using the combination of a high-HOMO-level blue phosphor and high-HOMO-level poly(arylene phosphine oxide) host to achieve a low turn-on voltage of 2.8 V, high external quantum efficiency of 18.0% and remarkable power efficiency of 52.1 lm W−1, which makes them the most efficient SWPs so far. This record power efficiency is realized by using the high-HOMO-level blue phosphor to eliminate the hole scattering effect and by using the high-HOMO-level polymer host to reduce the hole injection barrier. This result represents an important progress in SWPs to achieve efficiency surpassing that of the polymer blends currently used for solution-processed white organic light-emitting diodes (WOLEDs) and even comparable with that of the small molecules used for vacuum-deposited WOLEDs.

Through-space charge transfer hexaarylbenzene dendrimers containing circularly-arrayed electron donors and acceptors exhibit thermally activated delayed fluorescence and aggregation-induced emission effects, giving EQE of 14.2% for solution-processed OLEDs., Through-space electron interaction plays a critical role in determining the optical and charge transport properties of functional materials featuring π-stacked architectures. However, developing efficient organic luminescent materials with such interactions has been a challenge because of the lack of well-established prototypical molecules. Here we report the design of through-space charge transfer hexaarylbenzenes (TSCT-HABs) containing circularly-arrayed electron donors (acridan/dendritic triacridan) and acceptors (triazine), which exhibit both thermally activated delayed fluorescence (TADF) and aggregation-induced emission (AIE) effects for high-efficiency solution-processed organic light-emitting diodes (OLEDs). Spatial separation of donors and acceptors in the TSCT-HABs induces a small singlet–triplet energy splitting of 0.04–0.08 eV, leading to delayed fluorescence with microsecond-scale lifetimes. Meanwhile, the TSCT-HABs display the AIE effect with emission intensity enhanced by 6–17 fold from solution to the aggregation state owing to their propeller-shaped configuration. Solution-processed OLEDs based on the TSCT-HABs show maximum external quantum efficiency up to 14.2%, making them among the most efficient emitters for solution-processed TADF OLEDs.