The control of intraband carrier relaxation in semiconductor quantum dots (QDs) is a longstanding topic of interest due to its central role in QD optoelectronic technologies. Applications such as hot carrier solar cells, mid-infrared detection and mid-infrared emission require a slow intraband relaxation. While the importance of multiphonon processes (“phonon bottleneck”) on intraband relaxation has been a debate over the past three decades, recent simulations [1-2] and experiments [1] suggest that QDs suffer from a fast intrinsic phonon decay lifetime of &lt;~1 nanosecond. This bottleneck is a serious limitation, as it sets a fundamental limit on performance of QD mid-infrared optoelectronics.<br/><br/>In order to slow the nonradiative decay and study the underlying relaxation mechanism, we report [3] the synthesis of thick CdS shells on HgSe QDs. To access the intraband transition, we n-dope the QDs by introducing an electric dipole on the QD surface. At low doping and large shell thickness, photoluminescence lifetime and quantum yield (QY) measurements show that HgSe/CdS QDs achieve an intraband QY of 2% and lifetime in excess of 10 ns. These results suggest that multiphonon relaxation in QDs can be much slower than previously predicted, and highlight the promise of QDs for mid-infrared detection and emission.

Absence of intraband phonon bottleneck in thick-shell N-type HgSe/CdS core/shell quantum dots

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ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.