Hypsochromic Shift of Multiple‐Resonance‐Induced Thermally Activated Delayed Fluorescence by Oxygen Atom Incorporation

Abstract

Herein, we reported an ultrapure blue multiple‐resonance‐induced thermally activated delayed fluorescence (MR‐TADF) material (ν‐DABNA‐O‐Me) with a high photoluminescence quantum yield and a large rate constant for reverse intersystem crossing. Because of restricted π‐conjugation of the HOMO rather than the LUMO induced by oxygen atom incorporation, ν‐DABNA‐O‐Me shows a hypsochromic shift compared to the parent MR‐TADF material (ν‐DABNA). An organic light‐emitting diode based on this material exhibits an emission at 465 nm, with a small full‐width at half‐maximum of 23 nm and Commission Internationale de l'Eclairage coordinates of (0.13, 0.10), and a high maximum external quantum efficiency of 29.5 %. Moreover, ν‐DABNA‐O‐Me facilitates a drastically improved efficiency roll‐off and a device lifetime compared to ν‐DABNA, which demonstrates significant potential of the oxygen atom incorporation strategy.

Solution‐Processable Pure‐Red Multiple Resonance‐induced Thermally Activated Delayed Fluorescence Emitter for Organic Light‐Emitting Diode with External Quantum Efficiency over 20 %

“…Benefiting from the highly rigid MR skeleton of BN‐R, the estimated the rate constant of the fluorescence radiative decay ( k F ) value is 3.8×10 7 s −1 , whereas the rate constants of the intersystem crossing ( k ISC ) and reverse intersystem crossing ( k RISC ) are 1.3×10 7 s −1 and 1.1×10 4 s −1 , respectively, which are comparable to most of the reported MR‐TADF materials [4–11] . Additionally, the experimental activation energies for ISC (Δ E a ISC ) and RISC (Δ E a RISC ) are calculated to be 3.2 and 110 meV, respectively, which are compared to those of most MR‐TADF materials and favorable to the mitigation of the temperature dependency of device performance, as shown in Figure 3f [6d] . Furthermore, superior morphological stability with a small root‐mean‐square (RMS) value of 0.696 nm for BN‐R was demonstrated by atomic force microscopy (AFM), which is crucial for solution processing devices (Figure S23a).…”

A Deep‐Blue‐Emitting Heteroatom‐Doped MR‐TADF Nonacene for High‐Performance Organic Light‐Emitting Diodes**

“…The same group modified the structure of v-DABNA by replacing one of the nitrogen atoms with a less electron-donating oxygen atom as in v-DABNA-OMe. [13] This emitter maintained efficient and narrowband blue emission (λ PL = 464 nm, FWHM = 24 nm in 1 wt % DABNA-OAr). The OLED with this derivative showed a slightly blue-shifted EL of 465 nm (FWHM = 23 nm, EQE max = 29.5 %).…”

Regioselective Transition‐Metal‐Free C(sp2)−H Borylation: A Subject of Practical and Ongoing Interest in Synthetic Organic Chemistry

“…It was also found that an OLED device employing 29 as a thermally activated delayed‐fluorescence (TADF) emitter exhibited excellent performance in blue OLEDs with an external quantum efficiency of 18.3 %. In a similar fashion, multiple C−H borylation reactions were achieved using electron‐rich polyaromatic compounds to produce various BN‐doped PAHs, including 32 , [64] 33 , [65] 34 , [66] and even the heterohelicene 35 , all of which are expected to have potential applications as electronic materials (Scheme 13b) [67] …”