Highly uniaxial alignment of pi-conjugated oligo(p-phenylenevinylene)s was spontaneously achieved in the as-cast films by simply spin-coating the solution onto mechanically rubbed polymer alignment layers such as poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonic acid) (PEDOT:PSS) film, resulting in a high dichroic ratio (A(//)/A(perpendicular to)) of 41.0 and an order parameter ([A(//) -A(perpendicular to)]/[A(//) + 2A(perpendicular to)]) of 0.93 estimated from the polarized absorption spectra of the films, and its application to organic photovoltaic devices was also demonstrated to achieve a high anisotropy in photosensitivity.