High-efficiency soluble thermally activated delayed fluorescent OLED with multilayer hole transport layers

Solution processed organic light emitting devices (OLEDs) incorporating a soluble thermally activated delayed fluorescent (TADF) emitter were fabricated with three hole-transport layers (HTL), poly(N-vinylcarbazole) (PVK), poly(9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine) (TFB), and TFB/PVK as the multilayer HTL. The device with multilayer HTLs demonstrated the highest external quantum efficiency (EQE) of 6.9%, the lowest driving voltage of 4.8V, and the highest luminance.