Colloidal quantum dots (CQD) attract much interest for optoelectronic applications, as potentially low-cost alternatives to epitaxial materials. In particular, in the mid-IR spectral range, CQD based on the zinc-blend mercury chalcogenides, Hg (S, Se, Te), lead efforts to create mid-IR technologies with solutions based materials. HgTe CQD with their tunable bandgap above 3 microns show promise as mid-IR detectors at a lower cost than existing HgCdTe (MCT) detectors. Progress towards the manufacture of mid-infrared cameras, improved sensitivity of PV devices, and new modalities, will be reviewed. HgS and HgSe CQDs also allow photodetection in the mid-IR because they are stably n-doped in ambient conditions, and they show an intense intraband transitions tunable in the mid-IR. Intraband CQDs is therefore another promising approach that broadens the types of materials considered. For both approaches, some of the challenges are similar, as one needs to develop tightly size-controlled colloidal quantum dots, and an interfacial chemistry that maximizes mobility and carrier lifetime, yet allows for controlling the doping.
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