Ultrasonic Spray-coating Films

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

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 and ultrasonic spray coating molybdenum trioxide (MoO3) films with the thickness of 60 nm are used as hole transport layer to realized hybrid OLEDs.

Ultrasonic spray coating MoO3 based OLED performs much better than Vacuum thermal evaporating MoO3 based OLED. Atom forces microscope images shows that both Vacuum thermal evaporating MoO3 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, ultrasonic spray coating MoO3 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 MoO3 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 ultrasonic spray coating MoO3 as hole transport layer are realized with low turn-on voltage, improved efficiency and stability.