Phosphonate-Substituted Conjugated Polymers for Interfacial Engineering in Polymer Solar Cells

Interfacial engineering has been identified as a fundamental strategy for maximizing the performances of organic electronic devices, such as light emitting diodes and organic solar cells. To this aim, water/alcohol soluble materials comprising a ?-conjugated backbone with pendant polar or ionic groups demonstrated to be quite effective as cathode interfacial layer (CIL), since they combine several advantages including: orthogonal solubility to solvent used to process the active layer, robust film formation, chemical flexibility in tailoring both the conjugated backbone as well as the polar/ionic functionalities. Among the polar side groups so far proposed to design CIL materials, phosphonate moieties have shown excellent interactions with aluminum electrode and inorganic semiconductors as indium tin oxide and zinc oxide [1-3]. Good interaction between ZnO nanoparticles (NPs) and phosphonate groups can be exploited to develop hybrid ZnO:polymer composite [3]. In this work, we have designed and synthesized a series of copolymers featuring phosphonate pendant groups. Their functional behaviour as cathode modifiers in polymer solar cells is herein investigated, for both pristine films and hybrid ZnO:polymer composites.