ABSTRACTThe infiltration of dissolved dyes into vertically aligned carbon nanotube arrays (va-CNT) is reported. The ultra hydrophobic surface of the CNT forest can be wetted and hence infiltrated for an appropriate choice of solvent. The dye-infiltrated CNT array forms a well ordered bulk-heterojunction structure for organic solar cells in which the CNT can act as a large electrode or, for appropriate energy levels, as an acceptor material. Derivatives of the small molecule copper phthalocyanine or the polymer poly(3-hexylthiophene) were used as dyes. Drop coating was chosen as the infiltration technique resulting in a completely embedded CNT forest. Field emission secondary electron microscopy analysis illustrates the final layer quality. Common electrical characterization under AM1.5 illumination proves photosensitivity and implies photovoltaic behavior of the composite.