Sub-meV Linewidths in Polarized Low-Temperature Photoluminescence of 2D PbS Nanoplatelets

TL;DR

This study demonstrates that ultrathin 2D PbS nanoplatelets exhibit extremely narrow photoluminescence linewidths, high polarization, and stable emission at low temperatures, highlighting their potential for quantum optical applications.

Contribution

First comprehensive low-temperature PL analysis of 2D PbS nanoplatelets revealing narrow linewidths, high polarization, and stable emission properties.

Findings

Linewidths down to 0.6 meV at 4K

High polarization degree up to 90%

Stable emission with no blinking over minutes

Abstract

Colloidal semiconductor nanocrystals are promising materials for classical and quantum light sources due to their versatile chemistry and efficient photoluminescence (PL) properties. While visible emitters are well-established, the pursuit of excellent (near-)infrared sources continues. One notable candidate in this regard are photoluminescent two-dimensional (2D) PbS nanoplatelets (NPLs) exhibiting excitonic emission at 720 nm (1.7 eV) directly tying to the typical emission range limit of CdSe NPLs. Here, we present the first comprehensive analysis of low-temperature PL from this material class. Ultrathin 2D PbS NPLs exhibit high crystallinity confirmed by scanning transmission electron microscopy, and revealing Moire patterns in overlapping structures. At 4K, we observe unique PL features in single PbS NPLs, including narrow zero-phonon lines with line widths down to 0.6 meV and a linear degree of polarization up to 90%. Time-resolved measurements identify trions as the dominant emission source with a 2.3 ns decay time. Sub-meV spectral diffusion and no immanent blinking over minutes is observed, as well as discrete spectral jumps without memory effects. These findings advance the understanding and underpin the potential of colloidal PbS NPLs for optical and quantum technologies.