Bipolar Thermally Activated Delayed Fluorescence Emitter with Balanced Carrier Transport for High-Efficiency Nondoped Green Electroluminescent Devices

High-efficiency electroluminescent devices featuring simplified architecture have received considerable attention due to significant advantages in construction procedures and commercialized applications.However,there still remains a critical challenge with regard to the lack of organic semiconductors that simultaneously possess high luminescent efficiency and balanced carrier-transporting abilities.Herein,we design a thermally activated delayed fluorescence(TADF)emitter 4-(9,9-dimethyl-9,10-dihydroacridine)-4′-triphenylphosphineoxide-benzophenone(DMAC-BPTPO)by incorporating triphenylphosphine oxide into the donor–acceptor skeleton.The accessional electrontransporting moiety,rod-like dimer,and horizontally packing model synergistically enable DMAC-BP-TPO which possesses an excellent photoluminescence quantum yield of nearly 90%with a reverse intersystem crossing rate constant of 2.0×106 s−1,horizontal dipole ratio of 89%,and a balanced electron and hole mobilities with a small constrast ratio of 1.08.Eventually,simplified electroluminescent devices including organic lightemitting diodes(OLEDs)and organic light-emitting transistors(OLETs)incorporating DMAC-BP-TPO-based nondoped film are demonstrated due to their superior integrated optoelectronic properties along with preferable horizontal dipole orientation.A record-high external quantum efficiency value of 21.7%and 4.4%are finally achieved in the simplified nondoped OLED and OLET devices,which are among the highest values in the related research fields.This work provides a new avenue to develop a high-efficiency bipolar TADF emitter to advance the simplified electroluminescent devices.