Browsing by Author "Henock Tadele"

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    Investigating the Doping Effects of Pb Concentration on the Optical & Electrical Properties of CdS Colloidal Quantum Dots
    (Addis Ababa University, 2024-08) Henock Tadele; Fekadu Gashaw
    In the present study, the doping effect of lead (Pb) atoms on the optoelectronic properties of cadmiumsulfide (CdS) colloidal quantumdots is investigated. The concept of quantum confinement has been explored, emphasizing the role of QuantumMechanics and the effective mass approximation in understanding confinement energy. Experimental synthesis of CdS colloidal quantumdots was performed using a modified method of chemical bath deposition technique. The resulting quantum dots exhibited a bright yellow vibrant color. UV-Vis and PL studies revealed a redshift followed by a blueshift at increased Pb concentrations. Tauc plot analysis determined the bandgap values to be 2.70eV, 2.67eV, 2.72eV, 2.74eV and 2.77eV for pure, 0.10%, 0.15%, 0.20% and 0.25% doped samples respectively. This increase in bandgap was attributed to the Burstein-Moss effect. FTIR characterization showed shifts and intensity changes in peaks of the fingerprint region, indicating variations in molecular vibrations and stretching due to Pb doping. Optical analysis provided insights into the refractive index, dielectric constant, and linear optical susceptibility, which decreased with increasing bandgap. The electrical characterization showed decrease in resistivity and augmented conductivity by upto 7 times from the undoped sample with higher Pb concentrations. Moreover, the IV curve exhibited an ohmic nature, suggesting the samples resemble metallic conductor properties.