Wavelength-conversion encapsulant composition, wavelength-conversion encapsulant layer, and solar cell module using same

The present invention relates to providing a solar-cell-use wavelength-conversion encapsulant layer of high durability, which is also cost-advantageous, and which can improve photovoltaic efficiency of a solar cell by wavelength-converting light of a wavelength region that does not contribute to power generation to light of a wavelength region that does contribute to power generation. The wavelength-conversion encapsulant composition comprises first organic material which absorbs ultraviolet light and converts the same to light of a wavelength longer than the absorbed light, and second organic material which absorbs light of a wavelength longer than the first organic material and converts the same to light of a wavelength longer than the absorbed light, said wavelength-conversion encapsulant composition being characterized in that the ratio of an index C 2 to an index C 1 (formula (1)) satisfies 0.001 ≤ C 2 / C 1 ≤ 0.5, where the index C 1 represents for the first organic material the product of the parts by weight P 1 in the wavelength-conversion encapsulant, the molar extinction coefficient e 1 , and the reciprocal of the molecular weight Mw 1 , and the index C 2 represents for the second organic material the product of the parts by weight P 2 in the wavelength-conversion encapsulant, the molar extinction coefficient e 2 , and the reciprocal of the molecular weight Mw 2 . (Formula (1)): C 2 / C 1 = [(P 2 × e 2 ) / Mw 2 ] / [(P 1 × e 1 ) / Mw 1 ]