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.

In this study, we synthesized and characterized multiresonant thermally activated delayed fluorescent (TADF) materials embedded with nitrogen-boron-oxygen (NÀ BÀ O), exhibiting color-tunability between blue and green, namely NBO, m-DiNBO, and p-DiNBO. The three emitter materials showed a high photoluminescence quantum yield (PLQY) and a state-of-the-art narrow full width at half maximum (FWHM) of 96 %/25 nm, 87 %/17 nm, and 99 %/19 nm, respectively. For m-DiNBO and p-DiNBO, the emission color could be tuned from blue to green by regulating the nonbonding/bonding molecular orbital characters. Owing to the expanded planar molecular structure, m-DiNBO and p-DiNBO showed high horizontal dipole ratio (Θ) of 88 % and 92 %, respectively. OLEDs were prepared with NBO, m-DiNBO, and p-DiNBO, exhibiting high external quantum efficiencies of 16.8 %, 24.2 %, and 21.6 %, respectively. NBO and m-DiNBO exhibited pure-blue emission with CIE coordinates of (0.137, 0.142) and (0.126, 0.098), respectively. p-DiNBO showed pure-green emission with a CIE coordinate of (0.258, 0.665).

The weak stability of a hole‐transporter upon approaching the anion state is one of the major bottlenecks for developing long‐life organic light‐emitting devices (OLEDs). Therefore, in this study, we developed a series of thermally and electrically stable hole‐transporters that are end‐capped with four dibenzofuran units. These materials exhibit i) high bond dissociation energy (BDE) toward the anion state, ii) a high glass transition temperature (Tg>130 °C), and iii) high triplet energy (ET>2.7 eV), thereby enabling approximately 20 % high external quantum efficiency (EQE) and significantly prolonging the stability of both thermally activated delayed fluorescent (TADF) and phosphorescent OLEDs with an operation lifetime at 50 % (LT50) of 20 000–30 000 h at 1000 cd m−2. In addition, investigating their structure‐property relationship revealed that ionization potential (IP), BDE, and Tg are critical prerequisites for the hole‐transporter to prolong lifetime in OLEDs.