Automated synthesis of InSb quantum dots with improved batch-to-batch reproducibility via kinetically matched co-reduction.

Abstract

Indium antimonide (InSb) colloidal quantum dots (CQDs) are attractive heavy-metal-free absorbers for infrared photodetection, yet their synthesis remains challenging because precursor reduction overlaps with nucleation and growth, hindering kinetic control and yielding broad size distributions. Here we employ an automated workflow to achieve precise control over InSb CQD synthesis, leading to improved batch-to-batch reproducibility and narrow size distributions without laborious post-synthetic size-selective precipitation. We find that InSb CQD formation proceeds through a kinetically matched precursor co-reduction pathway, which requires an In-rich environment to compensate for the faster reduction of Sb³⁺ precursor. Within this framework, we tune CQD size by modulating precursor conversion kinetics through In/Sb precursor molar ratio and reducing agent availability. This kinetically guided size control tunes the first excitonic absorption peak of CQDs across 1120-1650 nm in the short-wave infrared. Optimized CQDs with 0.825 eV bandgap exhibit a small Stokes shift of 32 meV, which is among the smallest reported for InSb CQDs.