Observation of the quantized motion of excitons in CdSe nanoplatelets

TL;DR

This paper reports the experimental observation of quantized exciton motion in ultrathin CdSe nanoplatelets due to in-plane quantum confinement, revealing discrete exciton states influenced by nanoplatelet size.

Contribution

First direct experimental evidence of exciton center-of-mass quantization in nanoplatelets, demonstrating size-dependent quantum confinement effects.

Findings

Exciton states become discretized with decreasing lateral size.

Photoluminescence and absorption spectra are affected by lateral confinement.

Quantization matches predictions of the particle-in-a-box model.

Abstract

We show that the finite lateral sizes of ultrathin CdSe nanoplatelets strongly affect both their photoluminescence and optical absorption spectra. This is in contrast to the situation in quantum wells, in which the large lateral sizes may be assumed to be infinite. The lateral sizes of the nanoplatelets are varied over a range of a few to tens of nanometers. For these sizes excitons experience in-plane quantum confinement, and their center-of-mass motion becomes quantized. Our direct experimental observation of the discretization of the exciton center-of-mass states can be well understood on the basis of the simple particle-in-a-box model.