Confinement Effect on the Excitonic Kinetic Energy of CdSe, CdS, and ZnS Semiconductor Nanostructures Using the Brus Effective Mass Model

Quantum confinement profoundly modifies the electronic and optical properties of semiconductor quantum dots (QDs), primarily by increasing excitonic kinetic energy as particle size decreases. This study examines the size-dependent excitonic kinetic energy of CdSe, CdS, and ZnS quantum dots using the Brus effective mass model. Analytical calculations reveal that excitonic kinetic energy rises sharply with decreasing quantum dot radius, following inverse-square dependence consistent with the spatial confinement of charge carriers. Among the materials studied, ZnS exhibits the strongest confinement due to its large reduced exciton mass and low dielectric screening, followed by CdS with intermediate behavior, and CdSe, which shows the weakest confinement owing to its small reduced mass and higher dielectric constant. These trends underscore the dominant role of intrinsic material parameters in determining excitonic sensitivity to confinement. The results provide critical theoretical guidance for the design and optimization of quantum dot–based optoelectronic devices, including photodetectors, light-emitting diodes, fluorescence probes, and other quantum-enabled technologies, where precise tuning of excitonic energy levels is essential.