Investigating Novel Luminescent Materials Towards Applications in Light Emitting Electrochemical Cells
Abstract
The search for new and better luminescent materials is becoming increasingly important, as there are significant cost-savings in using luminophores that are brighter and more efficient. Carbon quantum dots (CQDs) and other luminescent materials such as Pt-Ag nanoclusters and TADF compounds are an extremely appealing alternative to existing light-emitting materials, as they are low-cost, easy to synthesize, and non-toxic.
This thesis explores the properties and performance of different luminescent materials to be used in light-emitting electrochemical cells (LECs). In this work, we focused on LECs as their low cost and ease of fabrication aligns well with the ethos of CQDs and carbon-based nanomaterials. Firstly, we carried out some foundational work: developing a method to accurately determine the absolute quantum efficiency of the materials we tested. This method was tested using a variety of photodetectors to increase the analytical applicability, including photomultiplier tubes and spectrograph/CCD camera setups, and addresses many of the problems with reporting relative ECL efficiency. We also looked at several different novel materials – Pt-Ag bimetallic nanoclusters, and organic compounds that exhibit thermally activated delayed fluorescence (TADF) to enhance quantum efficiency – to evaluate their feasibility for use in LECs. In addition, we developed a set of computer simulations using COMSOL Multiphysics to model these light-emitting reactions. Using these models, we are able to learn important parameters, such as the bimolecular annihilation rate constant in electrochemiluminescence reactions, gain more knowledge about how these materials can emit light, and further optimize their luminous performance and efficiency.
In the final chapter of this thesis, we demonstrate our CQD-based LEC devices. These devices are the first example of CQDs being used in this fashion, and they exhibited bright white emission under electrical excitation. These CQDs, and, optimistically, derivatives of the material that are inspired by this work, are expected to be a substantial advancement in the research of next-generation, high performance light-emitting devices.