NOVELTY - A photocurable composition contains (in parts mass) monofunctional (meth)acrylate (100), saturated thermoplastic elastomer (30-80) and photoinitiator (0.1-10). The monofunctional (meth)acrylate is 15-26C alicyclic or aliphatic monofunctional (meth)acrylate. The saturated thermoplastic elastomer contains styrene-isobutylene diblock copolymer (40 %mass or more). The viscosity (V2) of the photocurable composition, measured using viscoelasticity measuring instrument equipped with cone and plate of diameter 25 mm as a measuring jig, is 30-300 Pa.second.    USE - Photocurable composition is used as sealing material for wet organic solar cell e.g. dye-sensitized solar cell (all claimed) for motor vehicles. Can also be used in clothing and curtain.    ADVANTAGE - The photocurable composition has excellent adhesiveness with respect to substrate. The wet organic solar cell formed using the photocurable composition has excellent sealing property, chemical resistance, battery performance, reliability and durability.    DETAILED DESCRIPTION - A photocurable composition contains (in parts mass) monofunctional (meth)acrylate (100), saturated thermoplastic elastomer (30-80) and photoinitiator (0.1-10). The monofunctional (meth)acrylate is 15-26C alicyclic or aliphatic monofunctional (meth)acrylate. The saturated thermoplastic elastomer contains styrene-isobutylene diblock copolymer (40 %mass or more). The viscosity (V2) of the photocurable composition, measured using viscoelasticity measuring instrument equipped with cone and plate of diameter 25 mm as a measuring jig (under conditions of temperature of 23 degrees C and rotation rate of cone-and-plate of 2 rpm), is 30-300 Pa.second. The ratio of the viscosity (V2) with respect to the viscosity (V20) of the photocurable composition, measured using the viscoelasticity measuring instrument (under the conditions of temperature of 23 degrees C and rotation rate of cone-and-plate of 20 rpm), is 1.3-20. An INDEPENDENT CLAIM is included for wet organic solar cell, which has a structure in which a photoelectric conversion layer consisting of organic compounds in an electrolyte solution which is enclosed between two substrates through a sealing layer, is positioned. The sealing layer is an optical curing material layer formed from the photocurable composition.