In this paper the effect of 5-(10-undecenyloxy)-2-[[[4-hexylphenyl] imino] methyl] phenol liquid crystal addition into poly(3-hexylthiophene): fullerene containing solar cells were investigated. Based on current-voltage characteristics, we report on the efficiency enhancement for bilayer heterojunction solar cells using this liquid crystal. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.