TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The metal electrode is made of aluminum or calcium. Preferred Method: The step of forming the metal electrode is to evaporate the metal on the photoactive layer.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: In the solar cell, a weight ratio of the electron donor to (I) is 1:0.2-1:5, preferably 1:1. The light-transmitting electrode is a patterned circuit. Preferred Method: The method of manufacturing the organic thin-film solar cell further comprises: forming a hole-transferring layer on the light-transmitting electrode; and performing an annealing step after the photoactive layer is formed, where the annealing step is performed under 20-250 (preferably 80-170) degrees C for 1 minute to 60 minutes, preferably 5-20 minutes.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (Claimed): Preparation of (I), comprises: reacting 2,2-dimethyl-1,3-dioxane-4,6-dione (IV) with a first alcohol, to obtain a first intermediate product, which is carboxylic acid compounds of formula (R1-O-C(=O)-CH2-C(=O)-OH) (II); esterifying a second alcohol with (II), to obtain a second intermediate product, which is a malonic ester derivative of formula (R1-O-C(=O)-CH2-C(=O)-O-R2) (III); and subjecting the second intermediate product and a fullerene to perform a Bingel reaction, to obtain (I).    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The electron donor is a conjugated polymer, preferably poly(3-hexylthiophene) (P3HT). The hole-transferring layer comprises poly(3,4-ethylenedioxy-thiophene) (PEDOT) and poly(styrene sulfonate) (PSS). Preferred Definitions:    F1 = C60 fullerene;    R1 = butyl;    n = 1; and    R2 = benzyl.    SPECIFIC COMPOUNDS - 1 Compound (I) is disclosed i.e. (benzylbutyl)(1,2-methanofullerene C60)-61,61-dicarboxylate of formula (Ia).    EXAMPLE - 2,2-Dimethyl-1,3-dioxane-4,6-dione (0.5649 g) was reacted with n-butyl alcohol (0.3712 g) in a bottle under 110-120 degrees C for 3 hours. Then, the un-reactive n-butyl alcohol was removed by using low-pressure distillation method and worked up to give malonic acid monobutyl ester (1a) (0.5337 g, 85%). 1a (0.5337 g), benzyl alcohol (0.4863 g), 1-hydroxybenzotriazole (45 mg, 10 wt/wt%), anhydrous tetrahydrofuran (5 ml) and anhydrous dichloromethane (20 ml) were added with N,N-dicyclohexylcarbodiimide (0.8253 g) in dichloromethane solution (5 ml) under cold-bath condition, stirred for 1 hour, and heated to 40 degrees C in oil bath for 24 hours. Next, the precipitate of dicyclohexyl urea was removed by using vacuum filtration method, and worked up to give malonic acid benzyl ester butyl ester (1b) (0.6668 g, 83%). 1b (87.6 mg), fullerene C60 (200 mg) and iodine (88.8 mg) were added with anhydrous toluene (200 ml) in a bottle, stirred for 1 hour, this was added with 1,5-diazabicycloundecen-5-ene (DBU) (60.8 mg) in toluene solution (10 ml) and reacted for 5 hours. Next, the DBU was removed by using vacuum filtration method, and worked up to give (benzylbutyl)(1,2-methanofullerene C60)-61,61-dicarboxylate (94.9 mg, 35%).