Towards photoelectrochromic modulation of NIR absorption in plasmonic ITO using pentacene films

Abstract

As a prototypical organic semiconductor material, pentacene is investigated in numerous electronic and optical systems for its high charge carrier mobility and attractive photophysical properties. However, charge generation, transfer and collection remain critical challenges, especially when considering hybrid structures with inorganic metal oxides as charge acceptors. Herein pentacene molecular layers are associated with plasmonic indium tin oxide (ITO) nanostructures, aiming to allow them to electrochromically modulate their near-infrared (NIR) absorption in the absence of external electric power. Multi-modal surface characterization shows that pentacene molecules transition from a perpendicular alignment when deposited on bare surfaces to more random organization, involving standing-up and face-on orientations, when deposited on ITO thin films. The optoelectronic properties of the interfaced materials are consequently impacted, with steady-state and ultrafast transient spectroscopies further highlighting how electrons are photogenerated in pentacene and consecutively transferred into plasmonic ITO, ultimately tuning its NIR optical response. Such ITO–pentacene bilayers therefore hold promise as novel heterojunction-like structures for the further innovative design of photoelectrochromic, self-powered smart windows.