TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation: No preparation method is given. Preferred Compounds: In the compound (I): each substituent on the phenyl is 1-4C alkoxy (preferably methoxy). The pendant group comprises 2,4,5,6-tetramethoxy-phenyl group. The pendant group further comprises an ester group (preferably COOCH3). The ester group and the phenyl group are spaced apart by at least two (preferably at least 4) carbon atoms. The fullerene group comprises 50-250 carbon atoms. The fullerene group is formed from C60, C70, C76, C78, C82, C84, or C92 fullerene. Alternatively the fullerene derivative comprises two fullerene groups bonded to the pendant group. The pendant group comprises two phenyl groups, each phenyl group substituted with four substituents and each substituent being, 1-10C alkoxy.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The photoactive layer in the photovoltaic cell (P1) further comprises an electron donor material. The electron donor material comprises: a polythiophene, polyaniline, polycarbazole, polyvinylcarbazole, polyphenylene, polyphenylvinylene, polysilane, polythienylenevinylene, polyisothianaphthene, polycyclopentadithiophene, polysilacyclopentadithiophene, polycyclopentadithiazole, polythiazolothiazole, polythiazole, polybenzothiadiazole, poly(thiophene oxide), poly(cyclopentadithiophene oxide), polythiadiazoloquinoxaline, polybenzoisothiazole, polybenzothiazole, polythienothiophene, poly(thienothiophene oxide), polydithienothiophene, poly(dithienothiophene oxide), polyfluorene, polytetrahydroisoindole, or their copolymers. SPECIFIC COMPOUNDS - 2 Compounds are specifically claimed as fullerene derivatives (I); i.e. 2,4,5,6-tetramethoxyphenyl-C61-butyric acid methyl ester (Ia); and 2,4,5,6-tetramethoxyphenyl-C71-butyric acid methyl ester.    EXAMPLE - To a solution of 5-(2,4,5,6-tetramethoxyphenyl)-5-(p-tosylhydrazono)-pentanoic acid methyl ester (1.03 g) in pyridine (20 ml), sodium methoxide (0.16 g) was added. The mixture was stirred at room temperature for 20-30 minutes, and a solution of C60 (fullerene) (1 g) in o-dichlorobenzene (80 ml) was added over 30 minutes. The mixture was stirred at 70 degrees C overnight. The reaction mixture was concentrated to 20-30 ml, purified on a column, re-dissolved in o-dichlorobenzene (50 ml), and stirred at 180 degrees C overnight. The mixture was concentrated to 10-20 ml, poured in methanol to form a precipitate, and filtered to obtain 2,4,5,6-tetramethoxyphenyl-C61-butyric acid methyl ester (Ia) (0.57 g) as a brown solid.