Solution-processed interlayer of discotic-based small molecules for organic photovoltaic devices: Enhancement of both the open-circuit voltage and the fill factor

A novel alcohol/water-soluble, discotic type derivative of pyrene was obtained using a simple synthesis process. The pyrene derivative was dissolved in organic solvents and highly polar solvents. The absorption spectrum of the pyrene derivative in a thin film was almost identical with that observed in solution compared with a fluorene derived co-polymer, the extensive planarity of the pyrene unit is invoked to rationalize this observation. According to an XRD measurement, a huge portion of the pyrene derivatives are arranged face-on in regard of the substrate due to their discotic structure. A photovoltaic device containing the pyrene derivative exhibited an open-circuit voltage of 0.73 V, current density of 14.6 mA/cm2, fill factor of 65.1% and a power conversion efficiency of 7.0%. The photovoltaic device with the pyrene derivative exhibited an improved fill factor compared with that of the fluorene co-polymer (60.7%) due to the discotic structure. An inverted photovoltaic device containing pyrene derivative showed a power conversion efficiency of 8.3%. © 2014 Elsevier Ltd. All rights reserved.