Influence of Morphology on Blinking Mechanisms and Excitonic Fine Structure of Single Colloidal Nanoplatelets

TL;DR

This study explores how the shape and surface quality of colloidal nanoplatelets influence their light emission stability and excitonic properties, revealing the role of hot carrier trapping and exciton localization.

Contribution

It demonstrates that PL blinking is driven by hot carrier trapping rather than Auger recombination and links shell roughness to nonradiative channels and exciton fine-structure splitting.

Findings

Hot carrier trapping significantly influences PL blinking.

Rough shells induce additional nonradiative channels.

Exciton fine-structure splitting is observed at room temperature.

Abstract

Colloidal semiconductor nanoplatelets (NPLs) with electronic structure as quantum wells have recently emerged as exciting materials for optoelectronic applications. Here we investigate how morphology affects important photoluminescence (PL) properties of single CdSe and core/shell CdSe/CdZnS nanoplatelets. By analyzing PL intensity-lifetime correlation and second-order photon correlation results, we demonstrate that, irrespective of morphology, Auger recombination cannot be responsible for PL blinking of single NPLs. We propose that hot carrier trapping plays a significant role in blinking and find that a rough shell induces additional nonradiative channels presumably related to defects or traps of an imperfect shell. Polarization-resolved PL spectroscopy analysis reveals exciton fine-structure splitting on the order of several tens of meV in rough-shell NPLs at room temperature, which is attributed to exciton localization and substantiated with theoretical calculations taking into account the NPL shape and electron-hole exchange interaction.