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

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 a critical challenge, especially when considering hybrid structures with inorganic metal oxides as charge acceptors. Herein, pentacene molecular layers are associated with plasmonic electrochromic indium tin oxide (ITO) nanostructures so to allow them to electronically modulate their near-infrared (NIR) absorption in absence of external electric power. Multi-modal surface characterizations show that pentacene molecules transition from a perpendicular orientation when deposited on bare surfaces to more random organization, involving standing-up and face-on orientations, when deposited on ITO. Optoelectronic properties of the interfaced materials are consequently impacted, with steady-state and ultrafast transient spectroscopies further highlighting how electrons are photo-generated in pentacene and consecutively transferred into ITO, ultimately tuning its NIR optical response. Such ITO – pentacene bilayers are therefore holding promise as novel heterojunction-like photoelectrochromic structures, paving the way for the innovative design of self-powered smart windows.