Halide-Driven Synthetic Control of InSb Colloidal Quantum Dots Enables Short-Wave Infrared Photodetectors.

In the III-V family of colloidal quantum dot (CQDs) semiconductors, InSb promises access to a wider range of infrared wavelengths compared to many light-sensing material candidates. However, achieving the necessary size, size-dispersity, and optical properties has been challenging. Here we investigate the synthetic challenges associated with InSb CQDs and find that uncontrolled reduction of the antimony precursor hampers the controlled growth of CQDs. To overcome this, we develop a synthetic strategy that combines non-pyrophoric precursors with zinc halide additives. Our experimental and computational studies show that zinc halide additives decelerate the reduction of the antimony precursor, facilitating the growth of more uniformly-sized CQDs. We also find that the halide choice provides additional control over the strength of this effect. The resultant CQDs exhibit well-defined excitonic transitions in spectral range of 1.26 eV to 0.98 eV, along with strong photoluminescence. By implementing a post-synthesis ligand exchange, we achieve colloidally stable inks enabling the fabrication of high-quality CQD films. We present the first demonstration of InSb CQD photodetectors reaching 75% external quantum efficiency (QE) at 1200 nm, to our knowledge the highest SWIR QE reported among heavy-metal-free infrared CQD-based devices. This article is protected by copyright. All rights reserved.