Selective Introduction of Carbazole and Diphenylamine into Spirofluorenexanthene Core for Different Phosphorescent Hosts

Built on the spiro[fluorene-9,9′-xanthene] (SFX) core and two frequently-used hole-transporting groups such as carbazole and diphenylamine, two SFX derivatives, namely SFXCz and SFXDPA, have been synthesized by one-step reaction for red, green and blue phosphorescent organic light-emitting devices (PHOLEDs). Though the properties of these two groups are very similar, the devices based on SFXCz and SFXDPA exhibit distinct performances. In blue PHOLEDs, the device based on SFXCz exhibited much better performances than that based on SFXDPA. However, the latter was superior to the former in green and red PHOLEDs. And the red PHOLED based on SFXDPA exhibited maximum current efficiency (CE) of 27.1 cd·A⁻¹, power efficiency (PE) of 25.0 lm·W⁻¹, and external quantum efficiency (EQE) of 15.0%. The results show that the introduction of diphenylamine group is suitable for constructing green and red host materials, whereas the introduction of carbazole group is suitable for constructing blue host materials.