High-Affinity Ligand-Enhanced Passivation of Group III–V Colloidal Quantum Dots for Sensitive Near-Infrared Photodetection

Group III–V colloidal quantum dots (CQDs) are promising infrared-absorbing materials that overcome the limitations of their regulated heavy-metal-containing counterparts, including Pb-, Cd-, and Hg-based materials. However, their surfaces and ligand chemistry remain unexplored, impeding sufficient ligand exchange. Therefore, approaches for selecting suitable exchange/passivation-enabling ligands for group III–V CQDs must be devised. Based on the hard–soft acid–base theory, diverse metal halide ligands and their interactions with InAs CQD surfaces were scrutinized in this study. Experimental investigations and density functional theory calculations indicated that hard-type Sn-based metal halide ligands exhibited a high affinity for the hard-type As-rich surface of InAs CQDs. Attaching different halides (X) affected the photoresponse performance of InAs-CQD-based devices. Here, high-affinity SnBr2 ligands were selected to fabricate the InAs-CQD-based photodiode, which exhibited the highest external quantum efficiency of 43.1% and responsivity of 0.36 A W–1 at an exciton peak of 1020 nm among previously reported InAs-CQD-based photodiodes.