Quantum dots (QDs) are nanometer-scale semiconductors with tunable bandgaps, making them ideal for optoelectronic devices like LEDs, photodetectors, lasers, and bioimaging tools. Their strong light absorption, tunable properties, and suitability for solution-based processing have driven interest in materials like lead halide perovskites, and cadmium, lead, and mercury-based chalcogenide QDs. However, their use is limited by toxic heavy metals, restricted by RoHS regulations. This has spurred demand for environmentally friendly alternatives, such as III-V QDs—particularly indium phosphide (InP) and indium antimonide (InSb)—which offer a wide bandgap range, high electron mobility, and strong covalent bonds. Despite their potential, the development of III-V QDs has faced challenges, including issues with precursor availability, high nucleation temperatures, and polydispersity.[1]

In our research, we have made significant advancements in the colloidal synthesis and surface chemistry of InP and InSb QDs.[2]  Using a heating-up method, we synthesized high-quality, monodisperse In-based QDs with size-tunable absorption features spanning from the visible to short-wave infrared range (445–1980 nm). To address the challenge of size tunability in InSb QDs, we developed various approaches to control their dimensions. For instance, different metal halides (InX₃, SbX₃, where X = Cl, Br, I) were employed as In and Sb precursors, with metal iodides producing the smallest InSb QDs among all tested halides. Additionally, the In-to-Sb ratio and the concentration of the reducing agent (super hydride) significantly influenced the QD size. A higher In/Sb ratio yielded larger QDs, while a higher concentration of super hydride resulted in smaller QDs, and vice versa. The resulting InSb QDs exhibited excellent colloidal and optical stability in non-polar solvents after four months. To enable their integration into highly conductive optoelectronic devices, we successfully exchanged the organic ligands of these QDs with various inorganic ligands, including metal halides, metal chalcogenides, and metal chalcogenide complexes. We elucidated the mechanisms behind the ligand exchange processes, facilitating the creation of QD inks capped with inorganic ligands. These inks were subsequently used to fabricate field-effect transistors, which exhibited enhanced conductivity. Our work marks a significant step in developing high-performance III-V-based optoelectronic devices, particularly in the infrared spectrum.