Colloidal InSb Quantum Dots for eSWIR Photodetection via Decoupling Nucleation and Growth

Colloidal InSb quantum dots (QDs) offer a critical heavy‐metal‐free platform for extended short‐wave infrared (eSWIR) optoelectronics. However, achieving the large QD sizes necessary to access the key eSWIR region beyond 1700 nm has remained a longstanding challenge, owing to the strongly coupled nucleation and growth inherent to the conventional one‐pot co‐reduction synthetic route. Here, a two‐step hot‐injection method is developed to address this limitation: low‐temperature co‐reduction generates intermediate nanoparticles, followed by injection into hot solvent to trigger crystallization and growth. This approach decouples coreduction‐reaction‐driven nucleation from diffusion‐controlled growth, enabling independent control over each stage. Optical and structural evolution reveals a nonclassical pathway: amorphous‐crystalline intermediates crystallize and grow via Ostwald ripening, with kinetics governed by the strength of solvent coordination. Using non‐coordinating nonadecene accelerates ripening, yielding monodisperse InSb QDs tunable from ∼5 to ∼12 nm with absorption covering 1600–2500 nm. Solid‐state ligand exchange with InCl 3 on the QD thin films constructs photoconductors with a room‐temperature responsivity of 45.77 mA W −1 and an external quantum efficiency (EQE) of 3.03% at 1875 nm, exceeding reported values for heavy‐metal‐free eSWIR photodetectors. This work establishes a synthetic pathway to eSWIR‐responsive InSb QDs and unlocks this heavy‐metal‐free system for high‐performance IR optoelectronics.