Colloidal quantum dots as solution-based nanomaterials for infrared technologies

This review focuses on the recent progress of wet-chemistry-based synthesis methods for infrared (IR) colloidal quantum dots (CQD), semiconductor nanocrystals with a narrow energy bandgap that absorbs and/or emits infrared photos covering from 0.7 to 25 micrometers. The sections of the review are colloidal synthesis, precursor reactivity, cation exchange, doping and de-doping, surface passivation and ligand exchange, intraband transitions, quenching and purification, and future directions. The colloidal synthesis section is organized based on precursors employed: toxic substances such as mercury- and lead-based metals and non-toxic substances such as indium- and silver-based metal precursors. CQDs are prepared by wet-chemical methods that offer advantages such as precise spectral tunability by adjusting particle size or particle composition, easy fabrication and integration of solution-based CQDs (as inks) with complementary metal-oxide-semiconductors, reduced cost of material manufacturing, and good performances of IR CQD-made optoelectronic devices for non-military applications. These advantages may allow facile and materials’ cost-reduced device fabrications that make CQD-based infrared technologies accessible compared to optoelectronic devices utilizing epitaxially grown semiconductors. However, precursor libraries should be advanced to improve colloidal infrared quantum dot synthesis, enabling CQD-based IR technologies to be available to consumer electronics. As the attention of academia and industry to CQDs continues to proliferate, the progress of precursor chemistry for IR CQDs could be rapid.