Synthesis of a perylene bisimide with acetonaphthopyrazine dicarbonitrile terminal moieties for photovoltaic applications

A symmetrical perylene bisimide (PERI) with tert-butylphenoxy side groups at the 1,7-bay positions of the perylene and acetonaphthopyrazine dicarbonitrile terminal moieties was synthesized and characterized. The long-wave absorption maximum of PERI was at 455 nm with thin film absorption onset at 583 nm corresponding to an optical band gap of 2.13 eV. We have used blend of PERI as electron acceptor with a dithyenylbenzoselenadiazole-based small molecule (Se-SM) as electron donor for the fabrication of bulk heterojunction photovoltaic devices. The power conversion efficiency (PCE) of the ITO/PEDOT:PSS/Se-SM:PERI/Al device using as cast active layer, is about 1.28% which is improved up to 3.88% when a thermally annealed blend is used as active layer. The improvement in the PCE has been associated with the enhanced crystallinity of the blend upon thermal annealing and the increase in hole mobility that results in improved charge transport.