We report highly efficient gas diffusion barriers for organic light emitting diodes (OLEDs) with an encapsulation structure composed of alternating magnesium fluoride (MgF(2)) and zinc sulfide (ZnS) layers grown by vacuum thermal deposition. The half lifetime of yellow OLEDs under an initial luminance of 2000 cd/m(2) with rubrene as an emitter reached 245 h using three pairs of MgF(2)/ZnS layers. The device lifetime was obviously improved using MgF(2) and ZnS as passivation layers before UV-cured epoxy seal without desiccant with the lifetime for the initial luminance dropping to 56% being over 500 h. This simple and inexpensive encapsulation method can potentially be applied to top-emitting OLEDs due to good light transmission characteristic of the passivation film. (c) 2010 Elsevier B.V. All rights reserved.