Engineering of CdSe, CdS, and ZnS Quantum Dots for Narrow Bandgap Devices Using the Effective Mass Approximation

International Journal of Material Science and Engineering

© 2025 by SSRG - IJMSE Journal

Volume 11 Issue 3

Year of Publication : 2025

Authors : G.C. Ogbu, O. K. Okongwu, E.N. Nwaru, U. D. Chukwuma, D. N. Ndubueze, S. C. Igbokwe, L. U. Uwenwa

10.14445/23948884/IJMSE-V11I3P103

How to Cite?

G.C. Ogbu, O. K. Okongwu, E.N. Nwaru, U. D. Chukwuma, D. N. Ndubueze, S. C. Igbokwe, L. U. Uwenwa, "Engineering of CdSe, CdS, and ZnS Quantum Dots for Narrow Bandgap Devices Using the Effective Mass Approximation," SSRG International Journal of Material Science and Engineering, vol. 11,  no. 3, pp. 11-14, 2025. Crossref, https://doi.org/10.14445/23948884/IJMSE-V11I3P103

Abstract:

This work presents a theoretical investigation of the size-dependent bandgap variation in CdSe, CdS, and ZnS Quantum Dots (QDs) using the Effective Mass Approximation (EMA) within the framework of the Brus equation. The model accounts for the intrinsic bulk bandgap, the quantum confinement contribution arising from carrier spatial restriction, and the Coulombic interaction between electrons and holes to predict bandgap energies across a radius range of 1–10 nm. Material specific parameters, such as effective electron and hole masses and dielectric constants, were extracted from established experimental data to ensure accurate estimation. The analysis shows that the effective bandgap energy increases markedly as the QD radius decreases, confirming the inverse relationship between size and bandgap. Among the examined materials, CdSe QDs demonstrate the greatest potential for narrow bandgap engineering, with their bandgap tunable from the bulk value of ~1.74 eV into the near-infrared regime at larger radii. By contrast, CdS and ZnS QDs, with higher intrinsic bandgaps (2.42 eV and 3.68 eV, respectively), exhibit stronger confinement-induced shifts and are therefore more suitable for ultraviolet and visible-light applications. Nevertheless, when employed in core–shell heterostructures such as CdSe/ZnS or CdSe/CdS, CdS and ZnS provide critical advantages in surface passivation, stability enhancement, and suppression of nonradiative recombination, while enabling CdSe cores to preserve their narrow bandgap functionality. Overall, this study reinforces the effectiveness of EMA in predicting quantum confinement effects in semiconductor nanocrystals and provides valuable theoretical guidance for the experimental synthesis and integration of CdSe-, CdS-, and ZnS-based QDs into next-generation optoelectronic and photonic devices.

Keywords:

Quantum Dots, Effective Mass Approximation (EMA), Brus Equation, CdSe, CdS, ZnS, Bandgap Engineering, Narrow Bandgap Devices, Optoelectronics.

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