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<p>This work presents a comprehensive investigation of the excitonic dynamics and photoluminescence (PL) characteristics of CdSe core and CdSe/CdSeS core–graded shell (CGS) quantum dots (QDs) under varying excitation power (PLP) conditions. Through power-dependent PL spectroscopy, we observe a clear redshift in emission energy indicative of band gap renormalization, driven by carrier–carrier Coulomb interactions. Compared to bare CdSe cores, the CGS-QDs demonstrate significantly enhanced PL intensity and narrower emission linewidths, attributed to effective passivation of surface traps and reduced interfacial defects enabled by the compositional gradient in the CdSeS shell. Raman spectroscopy combined with second-derivative analysis reveals distinct phonon mode shifts, linking strain relaxation and shell-induced lattice modulation to vibrational dynamics. Additionally, optical band gap values of 2.02&#xa0;eV (CdSe) and 1.94&#xa0;eV (CGS-QDs), determined via the Kubelka–Munk and Tauc plot methods, confirm strong quantum confinement and alloying-induced band gap bowing. The synergy between graded shell engineering and excitation power control offers new insights into how to tune electronic structure, excitonic recombination, and optical stability. These findings advance the rational design of high-efficiency QDs for next-generation optoelectronic, photonic, and bioimaging applications.</p>

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Tunable excitonic dynamics and photoluminescence modulation in graded CdSe/CdSeS quantum dots for optoelectronic applications

  • 期刊论文

  • 发表日期：

    2025年8月27日

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  • Nguyen Minh Hoa,
  • Le Anh Thi,
  • Le Xuan Hung,
  • Le Duc Toan

摘要

This work presents a comprehensive investigation of the excitonic dynamics and photoluminescence (PL) characteristics of CdSe core and CdSe/CdSeS core–graded shell (CGS) quantum dots (QDs) under varying excitation power (PLP) conditions. Through power-dependent PL spectroscopy, we observe a clear redshift in emission energy indicative of band gap renormalization, driven by carrier–carrier Coulomb interactions. Compared to bare CdSe cores, the CGS-QDs demonstrate significantly enhanced PL intensity and narrower emission linewidths, attributed to effective passivation of surface traps and reduced interfacial defects enabled by the compositional gradient in the CdSeS shell. Raman spectroscopy combined with second-derivative analysis reveals distinct phonon mode shifts, linking strain relaxation and shell-induced lattice modulation to vibrational dynamics. Additionally, optical band gap values of 2.02 eV (CdSe) and 1.94 eV (CGS-QDs), determined via the Kubelka–Munk and Tauc plot methods, confirm strong quantum confinement and alloying-induced band gap bowing. The synergy between graded shell engineering and excitation power control offers new insights into how to tune electronic structure, excitonic recombination, and optical stability. These findings advance the rational design of high-efficiency QDs for next-generation optoelectronic, photonic, and bioimaging applications.