# Synthesis of Monodisperse PbS/CdS Colloidal Quantum Dots Emitting at Telecommunication Wavelengths with suppressed Auger Rates and Gain Threshold

## TL;DR

Researchers synthesized PbS/CdS quantum dots that emit in the telecommunication range with improved optical stability and reduced nonradiative losses.

## Contribution

A novel synthesis method for PbS/CdS core–shell quantum dots with suppressed Auger recombination and low gain thresholds is introduced.

## Key findings

- PbS/CdS CQDs emitting at 1500–1620 nm were synthesized with high optical stability and narrow size distribution.
- Auger lifetimes increased up to 320 ps, and the gain threshold was reduced to ⟨N⟩gain≈ 1.7.

## Abstract

Semiconductor nanomaterials that combine high near-infrared
(NIR)
photoluminescence efficiency and photostability are limited. Pb-chalcogenide
colloidal quantum dots (CQDs), and particularly PbS CQDs, are promising
candidates. Nevertheless, the practical implementation of PbS CQDs
in optical devices faces intrinsic limitations due to the 8-fold degeneracy
of the conduction and valence bands, leading to enhanced nonradiative
Auger recombination, hindering applications such as lasing. Here,
we focus on the synthesis and optical characterization of core–shell
PbS/CdS CQDs emitting at telecommunication wavelengths (1500–1620
nm) with suppressed Auger rates. We synthesized three series of core/shell
PbS/CdS CQDs from different-sized PbS cores via a cation exchange
reaction. This approach produces PbS/CdS CQDs with high optical stability
and narrow size distribution. Finally, we optically probed the nanocrystals
with transient absorption, demonstrating suppressed Auger rates, increasing
biexciton Auger lifetimes τ
xx
up
to 320 ps, while reducing the gain threshold of the system down to
⟨N⟩gain≈ 1.7.