Four Dibenzofuran‐Terminated High‐Triplet‐Energy Hole Transporters for High‐Efficiency and Long‐Life Organic Light‐Emitting Devices

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. Four dibenzofuran‐terminated hole‐transporters exhibit superior thermal and electrical stability, thus realizing highly efficient and long lifetime thermally activated delayed fluorescent (TADF) and phosphorescent organic light‐emitting devices (OLEDs). A TADF OLED achieves an external quantum efficiency (EQE) of 23 % and operation lifetime (LT50) of over 20 000 h at 1000 cd m−2. Moreover, a phosphorescent OLED achieves an EQE of 21 % and LT50 of over 30 000 h at 1000 cd m−2.