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 (T_g>130 °C), and iii) high triplet energy (E_T>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 (I_P), BDE, and T_g are critical prerequisites for the hole-transporter to prolong lifetime in OLEDs.