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 InCl₃ 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.