| Abstract: | We demonstrate enhanced hole injection and lowered driving voltage in vacuum‐deposited organic light‐emitting diodes (OLEDs) with a hole‐transport layer using the starburst amine 4,4′,4″‐tris(N,N‐diphenyl‐amino)triphenylamine (TDATA) p‐doped with a very strong acceptor, tetrafluoro‐tetracyano‐quinodimethane (F4‐TCNQ) by controlled coevaporation. The doping leads to high conductivity of doped TDATA layers and a high density of equilibrium charge carriers, which facilitates hole injection and transport. Moreover, multilayer OLEDs consisting of double hole‐transport layers of thick p‐doped TDATA and a thin triphenyl‐diamine (TPD) interlayer exhibit very low operating voltages. |
