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Pendant engineering in multiple-resonance thermally activated delayed fluorescence to yield charge-transfer and locally excited-state characteristics. | LitMetric

AI Article Synopsis

  • Multiple-resonance thermally activated delayed fluorescence (MR-TADF) materials have narrow-spectrum features due to restricted molecular rotation, which could impact the design of organic light-emitting diodes (OLEDs).
  • This study synthesized various MR-TADF materials with different pendant groups and analyzed their excited states, spin-orbit couplings, and efficiency in OLEDs.
  • Results showed that the OLED using the neutral pendant (tDABNA-TP) achieved the highest external quantum efficiency (20.7%) and a significantly longer operating lifetime compared to those with donor and acceptor pendants.

Article Abstract

Multiple-resonance thermally activated delayed fluorescence (MR-TADF) materials can exhibit narrow-spectrum characteristics owing to the inhibition of rotation within the molecules. However, the excited states of these MR-TADF materials, which influence the spin-orbit couplings (SOCs) and device efficiencies of organic light-emitting diodes (OLEDs), have not been investigated to date. In this study, we synthesized MR-TADF materials tDABNA-TP, tDABNA-DN, and tDABNA-DOB by incorporating characteristic neutral, donor, and acceptor pendants into 2,12-di--butyl-5,9-bis(4-(-butyl)phenyl)-5,9-dihydro-5,9-diaza-13-boranaphtho[3,2,1-]anthracene (tDABNA). To determine the effect of pendant engineering, we investigated the excited states of the MR-TADF materials, including their singlet and triplet excited states, calculated the SOCs for their optimal reverse intersystem crossing pathways, and determined their maximum external quantum efficiencies (EQE) in OLEDs. The OLED with the emitter bearing the neutral pendant (tDABNA-TP) exhibited the highest EQE of 20.7% among those with the emitters bearing the donor (16.6%) and acceptor (12.4%) pendants, with a narrow emission range of 472-492 nm. Furthermore, the device with the tDABNA-TP emitter exhibited an operating lifetime of 196 h, which was 1.42- and 1.92-fold longer than those of the devices with the tDABNA-DN and tDABNA-DOB emitters, respectively. Our findings will promote research on the pendant engineering of MR-TADF-based OLEDs.

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Source
http://dx.doi.org/10.1039/d4nr03955fDOI Listing

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