Constructing multifunctional deep-blue emitters with weak charge transfer excited state for high-performance non-doped blue OLEDs and single-emissive-layer hybrid white OLEDs

Abstract

Deep-blue emitter with high photoluminescence efficiency (PLQY) is highly desirable in ultra-high definition displays and white solid-state lightings. In this work, two deep-blue phenanthro[9,10]imidazole derivatives, PPIS and PPPIS, with hot exciton property are successfully developed. Compared to PPIS, the embedded phenyl bridge in PPPIS is able to effectively increase the overlap of frontier molecular orbitals. In consequence, PPPIS shows higher oscillator strength and significantly enhanced PLQY. PPPIS also achieves better electroluminescence performance in non-doped device, showing deep-blue emission with Commission International de l'Eclairage (CIE) coordinates of (0.153, 0.087) and the maximum external quantum efficiency (EQEmax) of 8.5% with minuscule efficiency roll-off. Meanwhile, when PPPIS serves as the host for phosphor PO-01, high-efficiency orange phosphorescent device is obtained with high EQEmax of 29.8% and negligible efficiency roll-off at 1000 cd/m2. Further, efficient single-emissive-layer white device is assembled via utilizing PPPIS as a blue emitter as well as the host for PO-01 simultaneously, providing warm-white emission with CIE coordinates of (0.429, 0.433) at 1000 cd/m2, the forward-viewing EQEmax of 27.2% and maximum power efficiency (PEmax) of 80.1 lm/W, respectively. Our studies can establish a viable design strategy for deep-blue emitters in high-performance non-doped blue OLEDs and hybrid WOLEDs.