Quantum Shell in a Shell: Engineering Colloidal Nanocrystals for a High-Intensity Excitation Regime

Many optoelectronic processes incolloidal semiconductornanocrystals(NCs) suffer an efficiency decline under high-intensity excitation.This issue is caused by Auger recombination of multiple excitons,which converts the NC energy into excess heat, reducing the efficiencyand life span of NC-based devices, including photodetectors, X-rayscintillators, lasers, and high-brightness light-emitting diodes (LEDs).Recently, semiconductor quantum shells (QSs) have emerged as a promisingNC geometry for the suppression of Auger decay; however, their optoelectronicperformance has been hindered by surface-related carrier losses. Here,we address this issue by introducing quantum shells with a CdS-CdSe-CdS-ZnScore-shell-shell-shell multilayer structure.The ZnS barrier inhibits the surface carrier decay, which increasesthe photoluminescence (PL) quantum yield (QY) to 90% while retaininga high biexciton emission QY of 79%. The improved QS morphology allowsdemonstrating one of the longest Auger lifetimes reported for colloidalNCs to date. The reduction of nonradiative losses in QSs also leadsto suppressed blinking in single nanoparticles and low-threshold amplifiedspontaneous emission. We expect that ZnS-encapsulated quantum shellswill benefit many applications exploiting high-power optical or electricalexcitation regimes.

Automated summary

Many optoelectronic processes in colloidal semiconductor nanocrystals suffer from efficiency decline under high-intensity excitation due to Auger recombination. Semiconductor quantum shells have emerged as a promising solution for suppressing Auger decay, but their optoelectronic performance is limited by surface-related carrier losses. Introducing quantum shells with a CdS-CdSe-CdS-ZnS multilayer structure inhibits surface carrier decay and improves photoluminescence quantum yield, while retaining a high biexciton emission quantum yield. This improvement allows for longer Auger lifetimes and suppressed blinking in single nanoparticles, making ZnS-encapsulated quantum shells beneficial for applications with high-power optical or electrical excitation.