An excited state managing molecular design platform of blue thermally activated delayed fluorescence emitters by π-linker engineering

Abstract

A molecular design platform of blue thermally activated delayed fluorescence (TADF) emitters to boost the external quantum efficiency and efficiency roll-off of blue TADF organic light-emitting diodes (OLEDs) was developed.

Dipole Moment‐ and Molecular Orbital‐Engineered Phosphine Oxide‐Free Host Materials for Efficient and Stable Blue Thermally Activated Delayed Fluorescence

“…To explore their suitability as host materials for TADF emitter molecules, we investigated whether the excited‐state energies ( S 1 and T 1 ) of H1–H4 would be high enough to confine excitons within a given blue TADF emitter, 1PCTrz which has a typical structure of twisted intramolecular CT (TICT) molecules (Figure 2c). [ 23 ] Our calculations indicated that H1–H4 had sufficiently higher S 1 and T 1 values (Figure 2a, third panel) than the given TADF emitter. To verify the ground‐state polarities of the host materials and investigate their effect on the photophysical properties of the TADF emitter, we compared photoluminescence (PL) spectra of thin films composed of the given TADF emitter and host material.…”

1,3,5‐Triazine‐Functionalized Thermally Activated Delayed Fluorescence Emitters for Organic Light‐Emitting Diodes

“…The use of a phenyl substituent on the arylene bridge was explored by Lee et al [ 52 ] to modulate the conformation of the emitter. A cross‐comparison of the photophysical properties of 1PCTRZ (Φ PL : 87%; τ d : 55.8 μs; Δ E ST : 0.16 eV; 10 wt% in DPEPO) and 2PCTRZ (Φ PL : 90%; τ d : 31.4 μs; Δ E ST : 0.11 eV; 10 wt% in DPEPO) reveals how ortho ‐disubstitution leads to a more twisted conformation (dihedral angle for 1PCTRZ of 60.2° is smaller than that of 2PCTRZ of 68.2°), which translates into a smaller Δ E ST and a shorter τ d , but without negatively impacting Φ PL .…”

Bridge control of photophysical properties in benzothiazole-phenoxazine emitters – from thermally activated delayed fluorescence to room temperature phosphorescence

“…18,19 While a large number of TADF emitters can be found in the literature, and many make use of a p-bridge between the donor and acceptor parts of the molecule, only a few reports exist about the influence of this p-bridge on the photophysical properties of a given molecule and whether or not the p-bridge can be used to tune the emissive properties of the fluorophore. It has been illustrated that the introduction of such p-bridges, 20,21 and the addition of substituents such as methyl, 22 trifluoromethyl, 23 nitrile, 24 or extra phenyl groups 21,[25][26][27] onto these bridges, has a great impact on the emissive properties (e.g. colour, quantum yield, rate of (r)ISC) by restricting the rotational freedom, altering the acceptor strength, and/or increasing the space between donor and acceptor.…”