Uniform nanoribers composed of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] and its blends with poly(3-hexylthiophene) are formed by co-electrospinning their solutions with poly(vinyl pyrrolidone) (PVP) through a coaxial capillary system, followed by extraction of the PVP phase (see Figure). Compared with spin-cast films, the fibers show reduced phase separation and improved energy-transfer efficiency.