Cibalackrot Dendrimers for Hyperfluorescent Organic Light‐Emitting Diodes

Abstract

Hyperfluorescent organic light-emitting diodes (HF-OLEDs) enable a cascading Förster resonance energy transfer (FRET) from a suitable thermally activated delayed fluorescent (TADF) assistant host to a fluorescent end-emitter to give efficient OLEDs with relatively narrowed electroluminescence compared to TADF-OLEDs. Efficient HF-OLEDs require optimal FRET with minimum triplet diffusion via Dexter-type energy transfer (DET) from the TADF assistant host to the fluorescent end-emitter. To hinder DET, steric protection of the end-emitters has been proposed to disrupt triplet energy transfer. In this work, the first HF-OLEDs based on structurally well-defined macromolecules, dendrimers is reported. The dendrimers contain new highly twisted dendrons attached to a Cibalackrot core, resulting in high solubility in organic solvents. HF-OLEDs based on dendrimer blend films are fabricated to show external quantum efficiencies of >10% at 100 cd m −2 . Importantly, dendronization with the bulky dendrons is found to have no negative impact to the FRET efficiency, indicating the excellent potential of the dendritic macromolecular motifs for HF-OLEDs. To fully prevent the undesired triplet diffusion, Cibalackrot dendrimers HF-OLEDs are expected to be further improved by adding additional dendrons to the Cibalackrot core and/or increasing dendrimer generations.

High-Efficiency Functional Materials: Challenges and Developments in Solution and Dry Processed Green OLEDs

“…Adachi and Shih et al in 2022 reported the first HF-OLEDs based on dendrimers, which were macromolecules with highly defined structures. 107 The dendrimers' showed a high solubility in most of the organic solvents and it was due to the addition of fresh, highly twisted dendrons to a cibalackrot core. Dendrimer mixed films were used to create HF-OLEDs that had EQE greater than 10% at 100 cd m −2 .…”

High‐Efficiency Area‐Emissive White Organic Light‐Emitting Transistor for Full‐Color Display

“…Following this, the singlet excitons were transferred to FIrpic and rubrene, respectively, via Förster resonance energy transfer (FRET). [37][38][39] The singlet excitons in FIrpic converted to triplets rapidly through efficient intersystem crossing (ISC) thanks to the Ir atom for improving the spin-orbital coupling. Finally, the triplet excitons decayed to the ground state for a blue phosphorescent emission.…”

Suppressing the Undesirable Energy Loss in Solution‐Processed Hyperfluorescent OLEDs Employing BODIPY‐Based Hybridized Local and Charge‐Transfer Emitter

“…[17,18] But unfortunately, a primary undesirable energy loss channel, dexter energy transfer (DET) from the triplet state of TADF to the dark triplet state of the emitter, still exists in the HF-OLEDs that adversely affect the device's performance. [19,20] Hyperfluorescent organic light-emitting diodes (HF-OLEDs) approach has made it possible to achieve excellent device performance and color purity with low roll-off using noble-metal-free pure organic emitter. Despite significant progress, the performance of HF-OLEDs is still unsatisfactory due to the existence of a competitive dexter energy transfer (DET) pathway.…”

“…[ 17,18 ] But unfortunately, a primary undesirable energy loss channel, dexter energy transfer (DET) from the triplet state of TADF to the dark triplet state of the emitter, still exists in the HF‐OLEDs that adversely affect the device's performance. [ 19,20 ]…”