TECHNOLOGY FOCUS - ELECTRONICS - Preferred Device: The organic electronic device is a photovoltaic device.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: In the method, after step (c) and before step (d), a step (c') of maintaining the dispersion at the temperature T3 for a period long enough to achieve a stable crystalline nanofiber content in the dispersion is performed, where no annealing step is performed after step (d). The method further involves dissolving an amorphous polymer in the solution or dispersion before step (d). In the method, during step (b), a separation step for removing non fiber-like aggregates is performed. The dispersion obtained in step (b) comprises ratio crystalline nanofibers to dissolved nanofiber-forming polymer of at least 70:30. The temperature T1 is at least 20 (preferably at least 25) degrees C lower than the lowest temperature (Tm.d.) and at most 60 degrees C lower (preferably at most 50 degrees C) than the temperature Tm.d. at which the solvent completely dissolves the nanofiber-forming polymer. The temperature T1 is at least 50 degrees C (preferably at least 60 degrees C). The temperature T1 is such that the nanofiber-forming polymer dissolves at least partially or only partially in the solvent at the temperature T1. The T1 is such that solution of the nanofiber-forming polymer comprises less than 5 (preferably less than 1, especially less than 0.1)% aggregated nanofiber-forming polymer as measured by UV-Vis spectroscopy. The T1 is such that solution of the nanofiber-forming polymer is turbid or not limpid. The T2 is 0-25 (preferably 18-25) degrees C.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The nanofiber-forming polymer is a conjugated polymer. The conjugated polymer is a homo- or co-polymer comprising at least one monomer selected from thiophene, selenophene, thienylenevinylene, phenylene, phenylenevinylene, aniline, fluorene and indenofluorene or is a ladder-type poly(p-phenylene). The conjugated polymer has structure of formula (I). The electron acceptor is a fullerene derivative, preferably (6,6)-phenyl-61C-butyric acid methyl ester. The conjugated polymer is an electron donor and/or is a hole-conducting polymer.R=H or 1-10C alkyl, branched or linear or 5-10C cyclic alkyl. EXAMPLE - No suitable example is given.