Stepwise Crystallization Synthetic Strategy for Monodisperse InSb Colloidal Quantum Dots with Mid-Infrared Absorption.

Colloidal InSb quantum dots (QDs) are promising mid-infrared (MIR) photodetection materials due to their suitable bandgap, unparalleled room temperature electronic properties, environmental-friendly elemental composition, and facile solution processability. However, current InSb QDs suffer from limited spectral absorption within 2 µm, polydisperse QDs populations, and complex size-selective precipitation for further use, due to the lack of applicable growth theory and synthetic method. Here, we present a novel synthetic strategy for InSb QDs, which is featured by the initial formation of an amorphous intermediate and a subsequent stepwise crystallization process. This strategy enables the achievement of monodisperse InSb QDs with unprecedented 5.8-22.2 nm size range, and a remarkably low size distribution deviation of 5.8% without the need of any size-selective precipitation. For the first time, we realize the synthesis of InSb QDs with absorption wavelength exceeding 3000 nm, the record among the environmental-friendly QDs. The results presented here will pave the way toward environmental-friendly QDs as outstanding infrared optical and optoelectronic materials and push the frontier of solution-processed QDs into the mid-infrared regime applications.