Supramolecular charge transfer emitters: increasing efficiency in the near-infrared

New organic materials are critical to the advancement of functional, sustainable, and biocompatible technologies, fit for the 21st century. An excellent example are the emissive materials that underpin organic light-emitting diodes (OLEDs), devices which are energy-efficient and essential components of thin, lightweight, and flexible modern-day displays. OLEDs that operate in the near-infrared region of the spectrum also have fantastic potential, including for new technologies in healthcare. For example, near-infrared OLEDs would be used for blood oximetry skin patches, to provide continuous and non-intrusive oxygen monitoring, key to nursing Covid-19 patients and an ageing UK population. However, OLEDs are currently unsuitable for this application because the efficiency of organic emissive materials in the near-infrared is low, which hampers device signal strength. To address this problem, the aim of this project is to develop state-of-the-art organic emissive materials that are efficient in the near-infrared region.

The most promising OLED materials use electron-rich and electron-poor molecules, so-called donor-acceptor materials that exhibit thermally activated delayed emission. However, these materials currently have low efficiencies in the near-infrared, owing to a lack of structural control. This control is essential to optimising the electronic communication between donor and acceptor molecules. Here, supramolecular chemistry, the study of interactions between molecules, is ripe for exploitation.

This research project will use supramolecular chemistry to optimise donor-acceptor electronic communication, developing novel molecular architectures to boost the efficiency of their near-infrared emission, for OLEDs. A comprehensive scientific understanding of this new supramolecular approach will be realised through specialist spectroscopic experiments to establish structure-property relationships. This work will arm chemists with a new blueprint of design for donor-acceptor materials, benefiting a broad range of research fields, including organic optoelectronics, catalysis and bioimaging. The new emitters will be used to prepare fluorescent materials, where again supramolecular chemistry will be key in translating efficiency from solution to thin films. In the longer-term, these materials will be applied in near-infrared OLED devices, including for wearable medical diagnostics, thereby furthering the project's socioeconomic impact.