Ligand-Mediated Shape Engineering of SWIR InAs Colloidal Quantum Dots for Photodetector Applications.

Abstract

Indium arsenide colloidal quantum dots (InAs CQDs) are promising candidates for next-generation short-wave infrared (SWIR) optoelectronics; however, synthesis using non-pyrophoric amino-arsine precursors has faced limitations in reaching long wavelengths (>1300 nm) due to intrinsic growth stagnation and challenging surface control. Herein, we report a robust strategy to synthesize high-quality SWIR InAs CQDs by introducing bulky oleic acid (OA) ligands to overcome these kinetic barriers. By modulating the interplay between the steric hindrance of OA ligands and the stabilization of (111) facets, we induce a controlled shape evolution from initial kinetically stabilized spheres to thermodynamically stable tetrahedrons. This morphological transition enables the achievement of the same absorption wavelength followed by a nearly fourfold reduction in nanocrystal volume compared to spherical counterparts. This mechanism offers a distinct pathway for the bandgap tunability of InAs CQDs enabling access to the SWIR region (>1700 nm) under mild reaction conditions (260-280°C). Furthermore, the OA-mediated surface chemistry unlocks the formulation of conductive halide-based inks, enabling photodetector development based on amino-arsine-synthesized InAs CQDs extending their spectral coverage to 1.6 um. The resulting photodetectors exhibit an external quantum efficiency of 19.1% at 1300 nm and D* of 3.4 × 10¹⁰ Jones.