In this research, the effect of surface roughness of flexible polymeric top cover layer on the efficiency of a dye-sensitized solar cell (DSSC) was investigated. In order to assess the durability of polyethylene terephthalate (PET) and polyethylene terephthalate naphthalate (PEN) the wear properties of these materials were first investigated. It was found that PEN was about 2.3 times more wear resistive than PET. PEN was used for further investigation regarding the effect of surface roughness on the light transmittance and electrical efficiency of DSSC. The surface roughness of PEN was varied by sand blasting to simulate an erosion process. It was found that PEN with a maximum average surface roughness of 1.6 mu m resulted in 10% decrease in light transmittance and consequently degraded the cell efficiency of DSSC by 13%. The decrease in electrical efficiency due to increasing surface roughness was found to be proportional to the light transmittance. (C) 2012 Elsevier Ltd. All rights reserved.