Localization and Multi-Exciton Dynamics in Superionic Canfieldite Ag8SnS6@Zn Nanocrystals

Abstract

An exciting new member of the ternary Ag-based nanocrystal (NC) family is found in canfieldite Ag8SnS6@Zn (ATS@Zn) NCs, which offer a prospect for size-tunable optical properties in the red to near-infrared spectrum. Despite their promise, a lot of questions on the nature of their light–matter interactions, and related (multi-) exciton photophysics, remain unexplored. Furthermore, as to how the superionic character found in bulk ATS plays a role in NCs is unclear. Herein, we have systematically investigated the size-dependent single- and multi-exciton dynamics in superionic canfieldite ATS@Zn NCs, across widely different time and energy scales. Our results show that, whereas ATS@Zn NCs are strong light absorbers, a fast sub-picosecond hole localization quickly diminishes the oscillator strengths for radiative recombination. Multi-exciton states can be identified with fast non-radiative recombination pathways in line with Auger recombination. Overall, our results show that ATS@Zn NCs offer an interesting set of light–matter interactions for applications in light harvesting, priming in particular further research into the nature of the localization mechanisms at play.