Quinolinophenothiazine as Electron Rich Fragment for RGB Single-Layer Phosphorescent Organic Light-Emitting Diodes

The quinolinophenothiazine (QPTZ) fragment is a phenylacridine bridged by a sulphur atom. Despite appealing properties induced by this bridging (e.g. strong electron rich character), this fragment remains almost unexplored to date in organic electronics. Based on this QPTZ fragment, we report herein a high efficiency host for the new generation of simplified Phosphorescent Organic Light-Emitting Diodes so called Single-Layer (SL-PhOLEDs). This host material is constructed on the association of an electron rich fragment (QPTZ), and an electron-deficient fragment (2,7-bis(diphenylphosphineoxide)-fluorene). This molecule displays all the necessary properties to be used in universal SL-PhOLEDs. Red, green and blue SL-PhOLEDs were successfully fabricated and yielded an average external quantum efficiency of ca 10%. High luminances of ca 10000 cd/m2 for red and blue devices and 40000 cd/m2 for green devices were obtained. These luminances are higher than the best reported to date with structurally related analogues and highlight the strong interest of the QPTZ fragment in such devices. Thanks to its high HOMO level, the QPTZ unit also allows to decrease the threshold voltage, which is a key characteristic in the OLED technology. This work shows the potential of the QPTZ fragment in the design of host materials for high performance single-layer PhOLEDs.