Organic Interface Engineering for Stable Green PHOLEDs through an Ultrathin Interface Tunneling Layer

Abstract Device stability of the organic light emitting diodes is strongly affected by accumulated charge carriers at both interfaces of emitting layer (EML). To reduce the stress of devices from undesirable charge accumulation near EML, an interface tunneling layer (ITL) is introduced. Notably, ITL affects charge injection behavior, which helps to reduce a chemical degradation of EML. As a result, significantly improved device lifetime (by 2.5 times, ≈402.1 h, LT 75) after the introduction of pretty thin (1 nm) ITL between EML and electron transporting layer is obtained. Such a tunneling behavior by analysis of impedance spectroscopy (IS), ultraviolet photoelectron spectroscopy (UPS), and electric stress for electron and hole only devices are verified.