Electrochemical and Electrochemiluminescent Studies of InP/ZnSe/ZnSeS/ZnS Quantum Dots with Mechanistic Considerations

Semiconductor quantum dots (QDs), particularly InP-based systems, are emerging as low-toxicity alternatives to cadmium-based systems, offering tunable emission and high photostability. However, their characteristics and effectiveness as electrochemiluminescence (ECL) luminophores remain underexplored. Here, we investigate the electrochemical and electrochemiluminescent properties of InP/ZnSe/ZnSeS/ZnS QDs in both annihilation and coreactant pathways using cyclic voltammetry, differential pulse voltammetry, potential pulsing, photoluminescence, ECL spectroscopy, and UV-Vis absorption. We identify crystallization-induced emission (CIE) within the ECL pathway, resulting in a crystallization-induced blueshift (CIBS) relative to photoluminescence, indicating improved passivation effects. To our knowledge, this work reports the first quantification of absolute ECL efficiency (ΦECL) for InP/ZnSe/ZnSeS/ZnS QDs. A ΦECL of the QD/benzoyl peroxide (BPO) system was determined to be (6.69 ± 0.02) × 10−4 % using cyclic voltammetry, while 0.5 Hz potential pulsing increased the efficiency nearly eightfold to (5.38 ± 0.59) × 10−3 %. This enhancement demonstrates that the ECL emission is strongly governed by kinetic factors, where rapid and simultaneous generation of radical species promotes efficient electron-transfer reactions, minimizing losses from radical decay and diffusion limitations. These results establish InP-based QDs as promising ECL emitters and provide mechanistic insight into how crystallization effects and electrochemical techniques jointly control emission efficiency, offering design principles for improved InP-based ECL systems.