TECHNOLOGY FOCUS - POLYMERS - Preparation (Claimed): Preparation of (I) comprises: reacting a poly(3-hexylthiophene)-based reversible addition-fragmentation chain transfer (RAFT) agent of formula (II) with vinylbenzyl chloride and styrene via reversible addition-fragmentation chain transfer (RAFT) polymerization to synthesize a rod-coil copolymer; reacting the rod-coil copolymer with sodium azide to synthesize a rod-coil block copolymer having an azide group; and reacting the rod-coil block copolymer having an azide group with fullerene via 1,3-dipolar cycloaddition to give (I), with a nitrogen bridge introduced into fullerene.q = 40-200. EXAMPLE - Poly(3-hexylthiophene) having a terminal trithiocarbonate group (0.1 g) as a macro-reversible addition-fragmentation chain transfer (RAFT) agent, azobisisobutyronitrile (AIBN) (0.75 mg) as an initiator, and anhydrous toluene (2.5 ml) were added to a Schlenk flask that had been purged with argon gas for 15 minutes. To the resulting mixture solution, a mixture of styrene (2.2 g), p-vinylbenzyl chloride (0.407 g) and anhydrous toluene (3 ml) was added. After removing gas in the flask through 3 freeze-pump-thaw cycles, dried argon gas was injected. Then the flask was immersed in an oil bath of 70-75 degrees C for 24 hours to prepare a polymer solution. After precipitating the polymer solution by adding methanol (200 ml), the precipitate was recovered by centrifugation, and then dissolved in ethyl acetate solution at 70 degrees C. The undissolved, unreacted poly(3-hexylthiophene) was filtered off and ethyl acetate was evaporated from the filtrate and worked up to give a rod-coil block copolymer poly(3-hexylthiophene)-poly(styrene(89)-benzyl chloride(11)). Then poly(3-hexylthiophene)-poly(styrene(89)-benzyl chloride(11)) (350 g) and sodium azide (0.91 g) were added to a mixture solution of anhydrous dimethylformamide (DMF) (25 ml) and anhydrous toluene (25 ml) and stirred for 12 hours under reflux. The mixture was added to a solution (200 ml) of methanol and water of the same volume to obtain a solid polymer. The solid polymer was dissolved in tetrahydrofuran (THF), and subjected to precipitation by adding methanol (200 ml), and the precipitate was recovered by centrifugation, and dried in vacuum to give a rod-coil block copolymer having an azide group i.e. poly(3-hexylthiophene)-poly(styrene(89)-benzylazide(11)). Then poly(3-hexylthiophene)-b-poly(styrene(89)-benzylazide(11)) (300 mg), fullerene (0.2 g) and anhydrous o-dichlorobenzene (o-DCB) (200 ml) were added to the Schlenk flask and gas in the flask was removed via argon bubbling for 30 minutes. Then the mixture remaining in the flask was stirred at 60 degrees C for 2 days under argon atmosphere. Then, after heating to 130 degrees C and keeping at the temperature for 12 hours, the resulting mixture was concentrated under reduced pressure, and methanol (200 ml) was added. The resulting precipitate was dissolved in THF (500 ml) and filtered. The THF was evaporated from the filtrate and the residue was washed twice with hexane. The resulting crude product was dissolved again in THF (500 ml) and filtered. Then the THF was evaporated from the filtrate, to obtain a solid, which was dissolved in a small quantity of o-DCB solution and then precipitated in hot hexane solution. The unreacted fullerene was repeatedly dissolved in a small quantity of o-DCB solution and then precipitated in hot hexane solution, to obtain the donor-acceptor rod-coil diblock copolymer i.e. poly(3-hexylthiophene)-poly(styrene(89)-benzylazide(11))-fullerene.