Direct laser interference patterning (DLIP) is used to fabricate large area, two-dimensional periodic surface patterns on polyethylene terephthalate (PET) substrates to enhance the performance of ZnPc:C60 solar cells by light concentration in the absorber layer. Comparing the power conversion effi ciencies to the reference cell on fl at PET, a relative increase of 21% is observed for the hexagonal pattern with 0.7 mu m period, depicted in the fi gure.