In this study, the overall barrier performance of multilayer thin-films and the shelf lifetime of encapsulated organic solar cells were correlated through the total amount of water vapor that permeated into the solar cell. Effective water vapor transmission rates were measured in both the transient and steady-state transport regimes for multilayer barrier films consisting of SiNx and parylene. The efficiency of pentacene/C-60-based solar cells encapsulated with one or two pairs of SiNx/parylene dropped to 50% after permeation of about 1.63 g/m(2) of water vapor regardless of effective transmission rate of the barrier. From these calculations, cells encapsulated with three dyads were predicted to maintain performance for at least 13,500 h while experiments up to 7500 h showed less than 10% degradation in performance. (C) 2012 Elsevier B.V. All rights reserved.