Hybrid organic light-emitting device based on ultrasonic spray-coating molybdenum trioxide transport layer with low turn-on voltage, improved efficiency & stability

摘要

Hybrid organic light-emitting devices (OLEDs) employing inorganic oxides as carrier transport layer can further improve the performances of OLEDs, such as power efficiency, reduce turn-on voltage and enhance stability. Vacuum thermal evaporating (VTE) and ultrasonic spray coating (USC) molybdenum trioxide (MoO_3) films with the thickness of 60 nm are used as hole transport layer (HTL) to realized hybrid OLEDs. USC-MoO_3 based OLED performs much better than VTE-MoO_3 based OLED. Atom forces microscope images shows that both VTE-MoO_3 film and emitting layer deposited on it have an extremely rough surface, offering convenient entrance ports for the intrusion of oxygen and water vapor into organic function layer. Nevertheless, USC MoO_3 film and emitting layer deposited on it exhibit much smoother surface so that oxygen and water vapor must completely destroy the metal cathode before they intrude in the organic function layers. Besides, to prevent MoO_3 quenching excitons, host material with excellent hole transport property is used to restrict exciton recombination region at the interface between emitting layer and electron transport layer. As a result, hybrid OLEDs employing USC-MoO_3 as HTL are realized with low turn-on voltage, improved efficiency and stability.