Influence of surface roughness on the efficiency of a flexible organic solar cell

Abstract

Organic solar cells (OSCs) without an over-coating layer, consisting of a silver nanowire (AgNW) transparent electrode, a poly(3,4-ethylenedioxythiphene):poly (styrenesulfonate) (PEDOT:PSS) layer, a poly(3-hexylthiophene-2,5-diyl):the [6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM) active layer, a LiF/Al electron collecting, and a top electrode, were successfully fabricated in order to investigate the effect of surface roughness on the efficiency of OSCs. The AgNW transparent electrode on acryl resin coated polyethylene terephthalate (PET) film was prepared through the filtration/transfer method. Sheet resistance of 30 Omega(-1) and surface roughness of 10.5 nm were detected. After coating the PEDOT:PSS hole transfer layer and the P3HT:PCBM active layer at 1000 rpm on the AgNW/PET transparent electrode, the surface roughness was reduced dramatically. However, open circuit voltage, short circuit current density, fill factor, and power conversion efficiency decreased as the coating speed was raised during the formation of the PEDOT:PSS layer and the P3HT:PCBM active layer due to the deterioration of the surface roughness. The surface roughness was determined to be crucial for the output performance of OSCs.