TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: An electron acceptor is added to the solution or dispersion, before the coating step.    TECHNOLOGY FOCUS - POLYMERS - Preferred Component: The nanofiber-forming polymer is a conjugated polymer which is a homopolymer or copolymer comprising monomer(s) from thiophenes, selenophenes, thienylenevinylenes, phenylenes, phenylenevinylenes, anilines, fluorenes or indenofluorenes or is a ladder-type poly(p-phenylene). The conjugated polymer is electron donor and/or hole conducting polymer. The dispersion obtained in the cooling step comprises a ratio crystalline nanofibers to dissolve nanofiber-forming polymer of greater than or equal to 70:30, where the cooling step is performed at 0-25, preferably 18-25 degrees C. Preferred Structure: The conjugated polymer is of formula (I).R=H or 1-10C alkyl group, branched or linear or 5-10C cyclic alkyl group. EXAMPLE - Polymer/(6,6)-phenyl-61C-butyric acid methyl ester (PCBM) compositions in p-xylene were prepared with a Poly(3-hexylthiophene) (P36T) polymer of 0.7% with PCBM of 0.65%, 0.8%, and 1% respectively giving polymer/PCBM ratios of 1.07, 0.87 and 0.7 respectively and the nanofiber content investigated as a function of temperature. The nanofiber content was also investigated as a function of temperature for a polymer/PCBM composition in p-xylene with P36T- and PCBM-concentrations each being 1.0% giving a P36T/PCBM ratio of 1. The nanofiber-forming polymer of the polymer compositions had a crystalline nanofiber content of 80% at room temperature. A series of organic solar cells were fabricated using the polymer compositions on glass/indium tin oxide substrates. The substrates were cleaned in an ultrasonic bath with water and acetone. Then they were exposed to UV-ozone for 30 minutes. Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate was deposited by spin coating and dried for 15 minutes at 150 degrees C. Each polymer composition was deposited on different substrates by spin coating without any filtration under inert atmosphere (glove box). A calcium aluminide electrode was deposited by evaporation on each active layer obtained from the various polymer compositions. The active surface was 0.28 cm2.