Through-Space Conjugated Molecule with Dual Delayed Fluorescence and Room-Temperature Phosphorescence for High-Performance OLEDs

Abstract

Purely organic materials with room-temperature phosphorescence usually have much longer triplet state lifetimes than noblemetal containing phosphorescent materials, which lead to severe exciton quenching and inferior electroluminescence (EL) performance when applied in organic light-emitting diodes (OLEDs). Herein, a novel through-space conjugated molecule (2,3-PICz-XT) with dual delayed fluorescence and room-temperature phosphorescence is developed. Owing to suitable energy levels and strong spin−orbit coupling among excited states, 2,3-PICz-XT has short phosphorescence lifetimes at microsecond scale and high photoluminescence quantum yields in neat and doped films. 2,3-PICz-XT can function as efficient emitters in OLEDs, providing high external quantum efficiencies (η ext s) of up to 32.73% with small efficiency roll-offs. It can also efficiently sensitize various phosphorescent and thermally activated delayed fluorescence (TADF) materials to yield excellent EL performances. Impressively, the hyperfluorescence OLEDs using 2,3-PICz-XT as sensitizer for multiple resonance TADF materials attain narrow EL spectra and greatly improved η ext s over 35%. To the best of our knowledge, 2,3-PICz-XT is the most efficient emitter and sensitizer ever reported for dual delayed fluorescence and phosphorescence materials.

Solution-processed orange and white OLEDs sensitized by an electroactive pure organic room-temperature phosphorescent polymer

“…[5][6][7][8][9][10][11][12][13][14][15][16] As an alternative, TADF-sensitized fluorescence (TSF) and phosphorescence-sensitized fluorescence (PSF) have also been proposed to overcome the above 25% IQE limit. 2,[17][18][19][20][21] That is, TADF or phosphorescent molecules are adopted as the sensitizer for the conventional fluorescent emitters. In these cases, both singlet and triplet excitons can be harvested through an effective Fo ¨rster energy transfer from the sensitizer to the fluorescent dopant, leading to a near-unity IQE.…”

Molecular Engineering Modulating the Singlet–Triplet Energy Splitting of Indolocarbazole-Based TADF Emitters Exhibiting AIE Properties for Nondoped Blue OLEDs with EQE of Nearly 20%

“…The rapid intramolecular rotational and vibrational movements observed in solutions of AIE emitters are significantly reduced when they aggregate, leading to a considerable decrease in nonradiative decay and a notable enhancement of Φ PL . Furthermore, to mitigate the negative effects of aggregation-induced emission quenching and exciton annihilation, AIE emitters are typically designed with a twisted geometry, which results in weak intermolecular π–π interactions when in the aggregated state. , The twisted geometry also contributes to a small Δ E ST due to the spatial separation of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) wave functions. Therefore, AIE emitters often exhibit TADF characteristics.…”

Substitution position regulating the excitation-dependent fluorescence–phosphorescence emission of formylphenylboronic acids for single-component white light and anticounterfeiting

“…1 For example, phosphorescent organic light-emitting diodes (OLEDs) could theoretically achieve 75% exciton utilization. 2 In contrast, the best internal quantum efficiency of fluorescent OLEDs is only 25%. In the bioimaging field, the long lifetime of ORTP phosphors, ranging from milliseconds to seconds, would remove the interference of biological autofluorescence.…”

“…They could potentially produce two separate fluorescence and phosphorescence emission bands, which would find new applications in white-light emission and multicolor display. 2 a ,5 However, the phosphorescence intensity of most of the reported pure ORTP materials is much weaker than their fluorescence intensity under ambient conditions. 1 b , d ,4,6 A time-gated method is often used to measure the phosphorescence.…”

“…Minor modification in the molecule structure could induce a drastic change in phosphorescence performance, even the total disappearance of RTP. 2 a ,6 b – e Positional isomers have the same molecule compositions, but different configurations. This could result in different molecule packing after crystallizing from solution, which would affect the luminescence properties.…”