NOVELTY - A wavelength-conversion encapsulant composition comprises an organic material (A) which absorbs UV light and converts it to light of wavelength longer than the absorbed light, and an organic material (B) which absorbs light of wavelength longer than the organic material (A) and converts it to light of wavelength longer than the absorbed light. The ratio of an index (C2) to an index (C1) is 0.001-0.5.    USE - Wavelength-conversion encapsulant composition is used for forming wavelength conversion-type sealing material layer of solar cell module (all claimed).    ADVANTAGE - The economical wavelength-conversion encapsulant composition has high durability, and can improve photovoltaic efficiency of a solar cell by wavelength-converting light of a wavelength region which does not contribute to power generation to light of a wavelength region which does contribute to power generation.    DETAILED DESCRIPTION - A wavelength-conversion encapsulant composition comprises an organic material (A) which absorbs UV light and converts it to light of wavelength longer than the absorbed light, and an organic material (B) which absorbs light of wavelength longer than the organic material (A) and converts it to light of wavelength longer than the absorbed light. The ratio of an index (C2) to an index (C1) is 0.001-0.5, where index (C1) is product content (P1) of wavelength-conversion encapsulant in pts. wt. and molar extinction coefficient ( epsilon 1), and reciprocal of molecular weight (Mw1) of organic material (A), and index (C2) is product of content (P2) of wavelength-conversion encapsulant in pts. wt. and molar extinction coefficient ( epsilon 2), and reciprocal of the molecular weight (Mw2) of organic material (B2). An INDEPENDENT CLAIM is included for solar cell module (1), which comprises a photovoltaic cell (30) and a wavelength conversion-type sealing material layer (20) formed from wavelength-conversion encapsulant composition.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the solar cell module. (Drawing includes non-English language text)    Solar cell module (1)    Surface protective layer (10)    Wavelength conversion-type sealing material layer (20)    Photovoltaic cell (30)    Sealing material layer for back surfaces (40)