High-Efficiency Heterojunction Photovoltaic Devices by Block Copolymer Nanotemplates

摘要

Ultra high density arrays of conducting poly(pyrrole) (Ppy) and poly (3-hexyl thiopene) (P3HT) nanowires with diameters of 10approx.25 nm were prepared on indium-tin oxide coated glasses (ITO) by electropolymerization of the monomers inside nanoporous templated prepared by block copolymers. These high density arrays of conducting polymer nanowires could be used as P-type materials for photovoltaic devices. It was observed that even after the PS matrix was removed, the free standing conducting polymer nanowires persisted without collapsing the wire onto the substrate. Such structures could not be achieved by the electropolymerization of a conducting polymer inside an anodized aluminum oxide (AAO) membrane, where the nanowires were found to fall onto the substrate after the AAO was removed. After removal of the PS matrix, the HOMO and LUMO levels of Ppy nanowires were measured to be (question mark) 4.93eV and -3.69eV, respectively, which are slightly larger than the corresponding values (-4.79eV and -3.43eV) for Ppy thin films prepared by electropolymerization. Since the energy level of ITO glass is-4.8 eV, Ppy nanowires are more suitable for use as a P-type material. Due to the free standing geometry, a second N-type polymer can be easily spin-coated onto this array. Such arrays of polymer nanowires were also prepared on ITO-coated poly (ethylene terepthalate) film; demonstrating a new pathway to flexible photovoltaic devices.