NOVELTY - A rare-earth complex is a complex containing a rare-earth element chosen from praseodymium, europium, samarium, terbium, dysprosium, holmium and erbium. At least one type of 0.3-0.7 fluorine-containing ligand (a) ((A1)-(A11)), 0.8-1.2 nitrogen-containing ligand (b) ((B1)-(B7)), and 1.6-2.4 dioxo-containing ligand (c) ((C1)-(C13)) are coordinated to the rare-earth element, each with respect to one atom of rare-earth elements.    USE - Rare-earth complex is used for resin solution and resin composition for wavelength conversion sheet e.g. anti-reflection sheet, and sealing agent for solar cell module (all claimed).    ADVANTAGE - The rare-earth complex has high light resistance with respect to europium complex, and provides solar cell module having high efficiency, and ultraviolet light and blue light absorption and emission property.    DETAILED DESCRIPTION - A rare-earth complex is a complex containing a rare-earth element chosen from praseodymium, europium, samarium, terbium, dysprosium, holmium and erbium. At least one type of 0.3-0.7 fluorine-containing ligand (a) of formulae ((A1)-(A11)), 0.8-1.2 nitrogen-containing ligand (b) of formulae ((B1)-(B7)), and 1.6-2.4 dioxo-containing ligand (c) (c) of formulae ((C1)-(C13)) are coordinated to the rare-earth element, each with respect to one atom of rare-earth elements. The number ( alpha ) of components of ligand (a) per rare-earth element, and the number ( gamma ) of component of ligand (c) satisfies the relation: 2( alpha )+( gamma )=3-3.4.    X1,X2=aryl, heteroaryl, -C(CH3)3, -CH3, -CF3, -C2F5, -C3F7, or -C4F9.    INDEPENDENT CLAIMS are included for the following:    (1) resin composition, which comprises the rare-earth complex and resin;    (2) resin solution, which comprises the rare-earth complex, resin, and a solvent;    (3) wavelength conversion sheet, which consists of the resin composition;    (4) sealing agent, which consists of the resin composition; and    (5) solar cell module, which has photovoltaic cell and the wavelength conversion sheet arranged at the light-receiving surface side of the photovoltaic cell.