Steric Effect-Controlled Atomic Passivation of Colloidal InAs Quantum Dots for Infrared Photodetectors

Infrared colloidal quantum dots (CQDs) are emerging as promising materials for next-generation optoelectronics. Among these, III-V group CQDs have gained attention as lead-free alternatives. However, achieving efficient surface passivation remains a key challenge for high-performance lead-free CQD infrared optoelectronics. Herein, we present a sequential ligand adsorption model using density functional theory, integrated with systematic experiments, to thoroughly explore atomic ligand passivation, suited for indium arsenide (InAs) CQDs. We find that overall ligand adsorption dynamics-and thus the degree of surface passivation-are governed by ion-size-dependent steric hindrance and the electrostatic interactions of halide ligands. Smaller halide ligands enable more effective surface passivation and more balanced stoichiometry, leading to improved charge transport. As a result, an optimized InAs CQD photodiode exhibits a specific detectivity of 3.2 × 10¹² Jones at 980 nm.