Enhancing Electrochemiluminescence through Triplet State Dynamics

Abstract

Electrochemiluminescence (ECL) has attracted considerable interest for its applications in highly sensitive bioanalysis and emerging light-emitting display technologies, owing to its high signal-to-noise ratio, spatial precision, and controllable emission. The electrochemical generation of excitons through anion–cation annihilation enables the efficient formation of triplet states, offering an intrinsic quantum yield of up to 75% and allowing for low operating potentials. These characteristics make ECL systems inherently brighter and more energy efficient. Motivated by these advantages, this review focuses on the role of triplet-state dynamics in advancing ECL technologies. We detail the mechanistic pathways by which triplet excitons enhance annihilation-type ECL, covering foundational work on triplet–triplet annihilation (TTA) and recent developments in thermally activated delayed fluorescence (TADF), triplet–triplet energy transfer (TTET), and related mechanisms. Key characterization techniques and theoretical models used to identify and understand triplet-state involvement are summarized. Furthermore, we categorize major classes of triplet-based ECL luminophores—including metal complexes, organic molecules, and emerging nanostructures, with an emphasis on their structure–function relationships. Finally, we review current applications of triplet-functionalised ECL systems and outline the challenges and opportunities that lie ahead, highlighting the importance of continued research to fully exploit the potential of triplet-state processes in ECL.