Facile synthesis of multi-resonance ultra-pure-green TADF emitters based on bridged diarylamine derivatives for efficient OLEDs with narrow emission

Abstract

A series of multi-resonance ultra-pure-green TADF emitters based on bridged diarylamine derivatives is successfully developed for high efficiency and narrow emission OLEDs which exhibit a high EQE over 20% and narrow FWHM of less than 50 nm.

Narrowing the Electroluminescence Spectra of Multiresonance Emitters for High-Performance Blue OLEDs by a Peripheral Decoration Strategy

“…This design enables the emitter to realize a small Δ E ST and suppressed structural relaxation in the excited states concurrently, resulting in TADF with a narrowband emission as well as high photoluminescence quantum yields (PLQYs). A series of MR-TADF materials based on the B–N or carbonyl–nitrogen framework have been developed for high-performance TADF OLEDs with a small fwhm of as low as 18 nm and an external quantum efficiency (EQE) of up to 34%. − Nevertheless, compared to the conventional D–A-type TADF materials, the development of MR-TADF compounds is still in its infancy. The relationship between the chemical structures and their photophysical properties, including the efficiency and fwhm, still lags behind.…”

“…Decorating the B–N-based framework with substituent moieties is one of the most effective strategies to realize MR-TADF emitters with high efficiency, tunable emission, as well as a narrow bandwidth. For example, by rigidifying the peripheral phenyl groups of DABNA-1 with a sp 3 -carbon or heteroatom linkage, a series of MR-TADF materials have been developed with green emission. ,, The peripheral decoration of a carbazole-based MR-TADF skeleton BNCz with electron-withdrawing or -donating moieties at suitable positions has also been proved effective to realize the narrowband emission at longer wavelengths. ,− ,, However, the study of blue MR-TADF emitters with a peripheral decoration strategy is still rare. In addition, though many reported MR-TADF emitters exhibited extremely small fwhm’s in a dilute solution state, a few of them achieved electroluminescence (EL) spectra with the fwhm being smaller than 25 nm (0.14 eV) to meet the requirements of visual verisimilitude levels.…”

“…For example, by rigidifying the peripheral phenyl groups of DABNA-1 with a sp 3 -carbon or heteroatom linkage, a series of MR-TADF materials have been developed with green emission. 31,32,35 The peripheral decoration of a carbazole-based MR-TADF skeleton BNCz with electron-withdrawing or -donating moieties at suitable positions has also been proved effective to realize the narrowband emission at longer wavelengths. 19,[23][24][25]29,39 However, the study of blue MR-TADF emitters with a peripheral decoration strategy is still rare.…”

Efficient narrowband electroluminescence based on a hetero-bichromophore thermally activated delayed fluorescence dyad

“…Hereafter, TADF emitters with a narrow FWHM were widely studied and more chromophores with the MR effect were develeoped. [14][15][16][17][18][19][20][21] Among them, oxygen-bridged triarylboranes have also been exploited as narrowband emitters, and the parent molecule DABOA 14 (2a) exhibited a narrow emission (FWHM = 34 nm) with a l PL of 398 nm in solution. 22 In 2019, our group disclosed another successful example, QAO, which bears MR-TADF activity aside from the prevalent B/N or B/O system, which consisted of a triphenylamine having two para-disposed carbonyl bridges, and its electroluminescent device achieved an EQE of 19.4% with a narrow FWHM of 39 nm.…”

Donor Arylmethylation toward Horizontally Oriented TADF Emitters for Efficient Electroluminescence with 37% External Quantum Efficiency

“…As far as we know, both parameters are comparable to the best efficiencies of green TADF OLEDs reported heretofore. [ 8,10b,19 ]…”