NOVELTY - Photocurable composition comprises: (A) a photocurable monomer; (B) a silicon-containing monomer; and (C) a photopolymerization initiator.    USE - The photocurable composition is useful for encapsulated apparatus including flexible organic light emitting devices, organic light emitting devices, illumination devices, metal sensor pads, microdisc lasers, electrochromic devices, photochromic devices, microelectromechanical systems, solar cells, integrated circuits, charge coupled devices, light emitting polymers, or LEDs (all claimed).    ADVANTAGE - The photocurable composition exhibits fast response time, long durability, good light transmittance, and good moisture and oxygen barrier properties.    DETAILED DESCRIPTION - Photocurable composition comprises: (A) a photocurable monomer; (B) a silicon-containing monomer; and (C) a photopolymerization initiator. The silicon-containing monomer has a structure of formula (I).    X1, X2 = O, S, NH, or NRa1;    Ra1 = 1-10C alkyl, 3-10C cycloalkyl, or 6-10C aryl;    R1, R2 = 1-30C alkyl, 1-30C alkyl ether (both optionally substituted), a monoalkyl amine or dialkyl amine (having 1-30C alkyl, 1-30C thioalkyl, 6-30C aryl, 7-30C arylalkyl, 1-30C alkoxy or 7-30C arylalkoxy (all optionally substituted)), or H;    Z1, Z2 = H, or a monovalent group of formula (-R3-O-C(=O)-C(=CH2)-R4) (a), where at least one of Z1 and Z2 is (a);    R3 = 1-30C alkylene, 6-30C arylene, or 7-30C arylalkylene (all optionally substituted); and    R4 = H or optionally substituted 1-30C alkyl.    An INDEPENDENT CLAIM is included for an encapsulated apparatus comprising a member for the apparatus, and a barrier stack formed on the member for the apparatus and including an inorganic barrier layer and an organic barrier layer formed from the photocurable composition, where the organic barrier layer has an outgas generation of less than or equal to 1000 ppm, and a water vapor transmission rate of less than or equal to 5 g/m2(24 hours), as measured at 37.8 degrees C and 100% relative humidity (RH) for 24 hours at a layer thickness of the organic barrier layer of 5 mu m.    DESCRIPTION OF DRAWING(S) - The figure shows a sectional view of an encapsulated apparatus.    Substrate (10)    Apparatus (20)    Barrier stack (30)    Inorganic barrier layer (31)    Organic barrier layer. (32)