Near-Infrared Organic Photodiodes with Charge Transfer Absorption of Polymer Donor and Non-Fullerene Acceptor Mixture

Abstract

The need for a near-infrared (NIR) light source or detector is on the rise due to their application in various areas, e.g. pulse oximetry sensors, vein-imaging-based identification, and transparent organic photovoltaics. [1-4] In this respect, OPDs absorbing the light in the NIR spectral range are being studied intensively in recent years [4,5]. Among them, in particular, those with non-fullerene acceptors (NFA) have shown a very high performance partly for their good morphology and high molecule planarity [4]. This study aims at fully utilize the potential of the bulk heterojunction of conjugated donor polymers and NFA for the enhanced NIR sensitivity via charge transfer (CT) absorption between them. With the optimized optical design that strengthens CT absorption at a specific wavelength, we demonstrate NIR OPDs exhibiting the photosensitivity at a wavelength that is far longer than that corresponding to the nominal energy gap of the active materials (Fig. 1), illustrating that the proposed approach holds a great promise in detecting NIR photons with relatively long wavelengths.