Optical and electronic properties of confined exciton in a dot-in-rod structure

This study explores the excitonic properties of CdSe/CdS dot-in-rod nanostructures using the perturbation method within the effective mass approximation, combined with the finite element method. We analyze the first three excitonic energy levels (1S, 2S, and 3S), along with the electron and hole states, the exciton binding energy, and absorption coefficient for transitions between these levels under an applied electric field, as functions of the dot radius (R_c) and sidewall thickness (C). Our results reveal that the exciton binding energy reaches a maximum at a critical dot radius (R_c≃2nm), while excitonic energy levels decrease with increasing R due to quantum confinement effects. The applied electric field significantly modifies the exciton energy, increasing the first and third states while decreasing the second due to the quantum-confined Stark effect, which induces carrier polarization. The absorption coefficient for transitions among the 1S, 2S, and 3S peaks in an energy range comparable to experimentally observed photoluminescence spectra. Additionally, as R_c increases, the absorption peak undergoes a blue shift, whereas an increase in C results in a redshift and a slight enhancement in amplitude. These findings highlight the potential for tuning excitonic properties in optoelectronic and quantum applications.