[en] Highlights: • A inorganic SiN_x/SiO_xN_y hybrid barrier film prepared on a flexible substrate. • The SiN_x/SiO_xN_y hybrid barrier film shows WVTR of 7.1×10^-5 g m^-2 day^-1. • The PCE of encapsulated OSCs remained 86% of initial efficiency even after 2000 h. The science and technology of organic electronics have made consistent progress. However, the long-term stability of organic devices is a critical issue that remains to be resolved. Encapsulation is a straightforward and practical means to protect organic materials from oxygen or moisture and thus improve air stability. Here, we report a high-performance flexible inorganic SiN_x/SiO_xN_y hybrid barrier film for application in organic solar cells (OSCs). This hybrid barrier film shows average transmittance of 85.5% and a water-vapor transmission rate of 7.1×10^–5 g m⁻² day⁻¹. In OSCs comprising poly[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-bA]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl] thieno[3,4-b]-thiophenediyl] (PTB7) and [6,6]-phenyl-C₇₀-butyric acid methyl ester (PC₇₀BM), which were encapsulated by the SiN_x/SiO_xN_y hybrid barrier film, the power-conversion efficiency remained above 86% of the initial value even after 2000 h of storage in air, which is comparable to that obtained for a device encapsulated by a glass lid.