Unveiling the TADF Emitters with Apparent Negative Singlet-Triplet Gaps: Implications for Exciton Harvesting and OLED Performance

Xinrui Chen, Sergey Bagnich, Robert Pollice, Bing Li, Yuanyuan Zhu, Rishabh Saxena, Yixiao Yin, Weiguo Zhu, Alan Aspuru-Guzik*, Eli Zysman-Colman*, Anna Köhler*, Yafei Wang*

*Corresponding author voor dit werk

OnderzoeksoutputAcademicpeer review

1 Citaat (Scopus)

Samenvatting

Intramolecular through-space charge transfer thermally activated delayed fluorescence (TSCT-TADF) has attracted much attention recently as it can achieve both small energy splitting and high emission efficiency. However, the relationship of excited states between TSCT and through-bond charge transfer (TBCT) remains a challenge in the TSCT-TADF molecules. Herein, three compounds DPS-m-bAc, DPS-p-bAc, and DPS-OAc that possess emissive TSCT and/or TBCT states are prepared. Interestingly, a so-called inverted energy gap is found for both DPS-m-bAc and DPS-p-bAc in toluene solution, which results from the different charge transfer states of ICThigh and ICTlow, as proved by the detailed transient photoluminescence and calculated results. Intense emission from blue to yellow associated with high photoluminescence quantum yields of 70–100% are measured in doped polymethyl(methacrylate) (PMMA) films. Notably, compound DPS-m-bAc achieves the highest reverse intersystem crossing rate constant (kRISC) of over 107 s−1 in a PMMA film, benefiting from close-lying TSCT and TBCT states. The solution-processed device with DPS-m-bAc displays a maximum external quantum efficiency of 21.7% and a relatively small efficiency roll-off (EQE of 20.2% @ 100 cd m−2). Overall, this work demonstrates how with judicious emitter engineering, a synergy between different charge transfer excited states, can be achieved, providing an avenue to achieve highly efficient solution-processed OLEDs.

Originele taal-2English
Artikelnummer2301784
Aantal pagina's11
TijdschriftAdvanced optical materials
Volume12
Nummer van het tijdschrift6
DOI's
StatusPublished - 23-feb.-2024
Extern gepubliceerdJa

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