Exciton Binding Energy in CdSe Nanoplatelets Measured by One- and Two-Photon Absorption

Area of Science:

• Materials Science
• Condensed Matter Physics
• Quantum Dots

Background:

• Colloidal semiconductor nanoplatelets possess unique optoelectronic properties due to quantum confinement.
• The dielectric mismatch between nanoplatelets and ligands enhances Coulomb interactions.

Purpose of the Study:

• To investigate exciton binding energies in cadmium selenide (CdSe) nanoplatelets.
• To explore the impact of thickness on quantum confinement and Coulomb interactions.

Main Methods:

• Utilized one- and two-photon photoluminescence excitation spectroscopy.
• Measured exciton state energies (1S and 1P) in CdSe nanoplatelets with varying thicknesses (3-7 monolayers).
• Performed calculations using the effective mass approximation, including dielectric enhancement.

Main Results:

• Evaluated exciton binding energies ranging from 195-315 meV, approximately 20 times higher than in bulk CdSe.
• Observed that calculated effective Coulomb potentials align with the Rytova-Keldysh model for thin nanoplatelets.
• Found exciton binding energies comparable to those in monolayer transition metal dichalcogenides.

Conclusions:

• The strong quantum confinement and dielectric effects in CdSe nanoplatelets lead to significantly enhanced exciton binding energies.
• These findings highlight the potential of nanoplatelets for applications requiring strong light-matter interactions.
• The results provide valuable insights into the fundamental physics of low-dimensional semiconductor materials.