Tetraphenylcyclopentadiene-Based Hyperbranched Polymers: Convenient Syntheses from One Pot “A₄ + B₂” Polymerization and High External Quantum Yields up to 9.74% in OLED Devices

Through the A 4 + B 2 type Suzuki–Miyaura coupling reaction, hyperbranched polymers CP1, CP2, and CP3 were easily prepared, which exhibited high luminous efficiency in solution, neat film, and solid state as well as good thermal stability. When fabricated into organic light-emitting diodes (OLEDs) with mCP as host, the device based on CP1 demonstrated the good EL performance with external quantum efficiency (EQE) up to 6.36%. While the bipolar TADF host of CzAcSF was utilized instead of mCP, the driving voltage (at luminescence of 10 cd m –2 ) decreased from 5.7 to 4.4 V, and the EQE further increased to 9.74%, which was the highest EQE reported for hyperbranched polymers.