TECHNOLOGY FOCUS - POLYMERS - Preferred Method: The mixture of the at least one acceptor compound and the at least one poly(3-alkylthiophene) nanowire is prepared by: combining a first solution comprising the at least one acceptor compound in a first solvent with a suspension of the least one poly(3-alkylthiophene) nanowires in a second solvent; or combining a first solution comprising the least one acceptor compound in a first solvent with second solution comprising at least one poly(3-alkylthiophene)s in a second solvent. The step of depositing the mixture of at least one poly(3-alkylthiophene) nanowire and at least one bulk heterojunction solar cell acceptor compound onto the substrate comprises spin coating, drop coating, blade coating, spray coating or screen printing the mixture. The method further comprises thermal annealing the composite. Preferred Components: In the method, ratio of the acceptor compound to the poly(3-alkylthiophene) nanowire is 0.2:1-5:1 (weight ratio) in the mixture. The poly(3-alkylthiophene) nanowires comprise poly(3-alkylthiophene) comprising poly(3-methylthiophene), poly(3-ethylthiophene), poly(3-propylthiophene), poly(3-butylthiophene), poly(3-pentylthiophene), poly(3-hexylthiophene), poly(3-heptylthiophene), poly(3-octylthiophene), poly(3-nonylthiophene) and/or poly(3-decylthiophene). The acceptor compound is fullerene or fullerene derivative, an inorganic nanocrystal or semiconducting nanoparticle. The acceptor compound is (6,6)-phenyl-C61 butyric acid methyl ester, (6,6)-phenyl-C71 butyric acid methyl ester or (6,6)-phenyl-C85 butyric acid methyl ester. EXAMPLE - Nitrogen-degassed 1,2-dichlorobenzene (5 ml) was added to bottle containing poly(alkylthiophene) (P3BT) (30 mg). The resulting suspension (6 mg/ml) was stirred for 24 hours at 90-100 degrees C until P3BT was completely dissolved. The hot solution was filtered to obtain a filtrate. The filtrate was put in a dark environment for 72 hours to allow P3BT molecules to self-assemble to obtain poly(alkylthiophene) nanowires (P3BT-nw) in form of dispersion. Fullerene solutions (60 mg/ml) were prepared by dissolving fullerene (either (6,6)-phenyl-C61 butyric acid methyl ester (C61-PCBM) or (6,6)-phenyl-C71 butyric acid methyl ester (C71-PCBM)) in 1,2-dichlorobenzene at 40 degrees C under stirring and passing through 0.2 mu m filter. Poly(3-hexylthiophene):C71 PCBM (1:1) blend was prepared from poly(3-hexylthiophene) solution (30 mg/ml) and C71 PCBM solution (60 mg/ml). Poly(3-hexylthiophene):C61-PCBM (1:1 wt. ratio) blend was made by mixing just-filtered poly(3-hexylthiophene) solution (12 mg/ml) (0.5 ml) with C61 PCBM solution (0.1 ml) and warmed before spin coating of thin films. Poly(alkylthiophene)-nanowires suspension (1 ml) was mixed with C61-PCBM (0.1 ml) and C71-PCBM solutions (0.075 ml) to obtain poly(3-butylthiophene) (P3BT) nanowires/C61-PCBM (1/1 wt. ratio) and P3BT-nanowires/C71-PCBM (1/0.75 wt. ratio) nanocomposite.