Small-Band-Offset Perovskite Shells Increase Auger Lifetime in Quantum Dot Solids.

Colloidal quantum dots (CQDs) enable low-cost, high-performance optoelectronic devices including photovoltaics, photodetectors, LEDs, and lasers. Continuous-wave lasing in the near-infrared remains to be realized based on such materials, yet a solution-processed NIR laser would be of use in communications and interconnects. In infrared quantum dots, long-lived gain is hampered by a high rate of Auger recombination. Here, we report the use of perovskite shells, grown on cores of IR-emitting PbS CQDs, and we thus reduce the rate of Auger recombination by up to 1 order of magnitude. We employ ultrafast transient absorption spectroscopy to isolate distinct Auger recombination phenomena and study the effect of bandstructure and passivation on Auger recombination. We corroborate the experimental findings with model-based investigations of Auger recombination in various CQD core-shell structures. We explain how the band alignment provided by perovskite shells comes close to the optimal required to suppress the Auger rate. These results provide a step along the path toward solution-processed near-infrared lasers.