Barrier coatings, which prevent the permeation of water into organic photovoltaic devices fabricated on flexible plastic substrates, are essential to extend the device lifetime. Such protective coatings are made of multilayer stacks where multiple dense, inorganic layers are alternated with soft, organic ones. The approach described in this contribution consists in the deposition of multilayers in a large-area reactor, maintaining the same precursor and the same reactor configuration for both deposition of silica-like (through plasma enhanced chemical vapor deposition, PECVD, in microwave plasma) and organosilicon layers. A new process named initiated-PECVD was used for the formation of organosilicon polymers with planarization properties. The deposition of smoothening layers is demonstrated by depositing the coating on the top of a microsphere monolayer deposited over silicon wafers. The water vapor barrier performance of a 20-nm-thick SiO_x layer is two orders of magnitude improved when it is deposited on a planarizing layer compared to when it is deposited on the bare substrate. The mechanicals properties of the barrier stacks have been studied using nanoindentation. Three points bending tests demonstrate that the flexibility of the stack is sensibly improved when the inorganic layer is placed on the top of a low Young's Modulus layer.
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