Thin-film Encapsulation of Organic Light-Emitting Diodes Using Single and Multilayer Structures of MgF2, YF3 and ZnS

In this research, the lifetime of green organic light emitting diodes (OLEDs) is studied using four passivation layers. To encapsulate the OLEDs, MgF2, YF3, composed of alternating MgF2/ZnS and YF3/ZnS layers were grown by thermal vacuum deposition. Measurements show that the device lifetime is significantly improved by using YF3 and ZnS as passivation layers. However, diodes encapsulated by MgF2/ZnS and YF3/ZnS nano-structures show a highly efficient gas diffusion barrier that results in a longer lifetime of the devices. The half lifetime of the green OLEDs reached 1200 minutes using YF3/ZnS layers. The electroluminescence (EL) and current-voltage characteristics of the devices were also examined to compare the electrical and the emissivity properties of the devices before and after encapsulation. This simple and inexpensive thin-film encapsulation method would be potentially employed to capsulate top emitting OLEDs and flexible OLEDs due to their good performance and easy fabrication.