This perspective describes the advantages of infrared colloidal quantum dots (CQDs) for photodetection beyond silicon and provides a brief review of the development of CQD photodetection. The standard specifications for photodetectors are listed with particular emphasis on the detectivity. High gain improves the responsivity but does not improve the detectivity, while nonradiative losses do not prevent high responsivity but limit the detectivity. Performances of CQD detectors and HgTe CQDs, in particular, are compared with the maximum possible detectivity based on detailed balance from the device temperature and nonradiative losses.

HgTe colloidal quantum dots are investigated as the active material in photodiodes for extended short-wave infrared up to 2.6 μm. The HgTe colloidal quantum dots photodiodes achieve external quantum efficiencies above 50% and specific detectivities of 1 × 10¹¹ at 2.2 μm at room temperature with a microsecond response time and compete with commercial extended InGaAs photodiodes.