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 x 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 light emitting 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.