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

High Resolution Image Download MS PowerPoint Slide 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.