Ultrafast photophysical process of bi-exciton Auger recombination in CuInS2 quantum dots studied by transient-absorption spectroscopy

Auger recombination is an ultrafast and unnegligible photophysical process in colloidal semiconductor quantum dots (QDs) due to competition with charge separation or radiative recombination processes, pivotal for their applications ranging from bio-labeling, light-emitting diodes, QD lasing to solar energy conversion. Among diverse QDs, ternary chalcopyrite is recently receiving significant attention for its heavy-metal free property and remarkable optical performance. Given deficient understanding of the Auger process for ternary chalcopyrite QDs, CuInS2 QDs with various sizes are synthesized as a representative and the bi-exciton lifetime (tau(BX)) is derived by virtue of ultrafast time resolved absorption spectrum. The trend of tau(BX) varying with size is consistent with the universal scaling of tau(BX) versus QD volume (V): tau(BX) = gamma V. The scaling factor gamma is 6.6 +/- 0.5 ps.nm(-3) for CuInS2 QDs, and the bi-exciton Auger lifetime is 4-5 times slower than typical CdSe QDs with the same volume, suggesting reduced Auger recombination rate in ternary chalcopyrite. This work facilitates clearer understanding of Auger process and provides further insight for rational design of light-harvesting and emitting devices based on ternary chalcopyrite QDs. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

This study contributes to the understanding of the Auger process in ternary chalcopyrite QDs, revealing that the bi-exciton Auger lifetime is 4-5 times slower than typical CdSe QDs, providing insights for the rational design of optical devices based on ternary chalcopyrite QDs.