An organic power-generating layer comprising (i) an n-type semiconductor material consisting of a fullerene derivative having a purity of ≥ 99% as defined below, the fullerene derivative being represented by formula: wherein ring A is C 60 -fullerene; R 1 is C 1-6 -alkyl, or 1-naphthyl or 2-naphthyl, wherein 1-naphthyl or 2-naphthyl is each optionally substituted with at least one halogen atom; and Ar is phenyl, 1-naphthyl or 2-naphthyl, each optionally substituted with at least one C 1-8 -alkyl group, the purity being defined by the following equation: Purity % = 100 − D max % wherein the D max is the maximum value among the absolute value of the difference between an analysis value and a theoretical value obtained in elemental analysis of carbon, the absolute value of the difference between an analysis value and a theoretical value obtained in elemental analysis of hydrogen, and the absolute value of the difference between an analysis value and a theoretical value obtained in elemental analysis of nitrogen; the elemental analysis being conducted by burning each sample and measuring the obtained gases (CO 2, H 2 O, and N 2) using a CHN-Corder MT-6 elemental analyzer (Yanaco) to determine the amount ratio, and determining the mass percent of carbon, hydrogen, and nitrogen based on the amount ratio; and (ii) a p-type semiconductor material consisting of a donor-acceptor type π-conjugated polymer including as a donor unit benzodithiophene, dithienosilole or N-alkyl carbazole and as an acceptor unit benzothiadiazole, thienothiophene or thiophene pyrrole dione. (i) an n-type semiconductor material consisting of a fullerene derivative having a purity of ≥ 99% as defined below, the fullerene derivative being represented by formula: wherein ring A is C 60 -fullerene; R 1 is C 1-6 -alkyl, or 1-naphthyl or 2-naphthyl, wherein 1-naphthyl or 2-naphthyl is each optionally substituted with at least one halogen atom; and Ar is phenyl, 1-naphthyl or 2-naphthyl, each optionally substituted with at least one C 1-8 -alkyl group, the purity being defined by the following equation: Purity % = 100 − D max % wherein the D max is the maximum value among the absolute value of the difference between an analysis value and a theoretical value obtained in elemental analysis of carbon, the absolute value of the difference between an analysis value and a theoretical value obtained in elemental analysis of hydrogen, and the absolute value of the difference between an analysis value and a theoretical value obtained in elemental analysis of nitrogen; the elemental analysis being conducted by burning each sample and measuring the obtained gases (CO 2, H 2 O, and N 2) using a CHN-Corder MT-6 elemental analyzer (Yanaco) to determine the amount ratio, and determining the mass percent of carbon, hydrogen, and nitrogen based on the amount ratio; and ring A is C 60 -fullerene; R 1 is C 1-6 -alkyl, or 1-naphthyl or 2-naphthyl, wherein 1-naphthyl or 2-naphthyl is each optionally substituted with at least one halogen atom; and Ar is phenyl, 1-naphthyl or 2-naphthyl, each optionally substituted with at least one C 1-8 -alkyl group, the purity being defined by the following equation: Purity % = 100 − D max % R 1 is C 1-6 -alkyl, or 1-naphthyl or 2-naphthyl, wherein 1-naphthyl or 2-naphthyl is each optionally substituted with at least one halogen atom; and Ar is phenyl, 1-naphthyl or 2-naphthyl, each optionally substituted with at least one C 1-8 -alkyl group, the purity being defined by the following equation: Purity % = 100 − D max % wherein the D max is the maximum value among the absolute value of the difference between an analysis value and a theoretical value obtained in elemental analysis of carbon, the absolute value of the difference between an analysis value and a theoretical value obtained in elemental analysis of hydrogen, and the absolute value of the difference between an analysis value and a theoretical value obtained in elemental analysis of nitrogen; the elemental analysis being conducted by burning each sample and measuring the obtained gases (CO 2, H 2 O, and N 2) using a CHN-Corder MT-6 elemental analyzer (Yanaco) to determine the amount ratio, and determining the mass percent of carbon, hydrogen, and nitrogen based on the amount ratio; and (ii) a p-type semiconductor material consisting of a donor-acceptor type π-conjugated polymer including as a donor unit benzodithiophene, dithienosilole or N-alkyl carbazole and as an acceptor unit benzothiadiazole, thienothiophene or thiophene pyrrole dione.