Increased Organic Photovoltaic Cell Efficiency by Incorporating a Nonionic Fluorinated Surfactant Cathode Interlayer

The performance of an organic thin film photovoltaic cell was improved using a solution-processed fluorinated surfactant Zonyl (R) FS-300 (Zonyl) cathode interlayer. Poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) and [6,6]-phenyl C-71-butyric acid methyl ester ([70]PCBM) were used as the donor and acceptor, respectively, in the bulk-heterojunction photoactive layer. The spin-casting of the appropriate concentration of the Zonyl solution on the photoactive layer significantly and simultaneously improved the short-circuit current, open-circuit voltage, and fill factor. The optimized Zonyl treatment increased the power conversion efficiency from 3.53 to 4.76%. (C) 2012 The Japan Society of Applied Physics