Abstract
The chemistry of nanocrystals enables the receipt of semiconductor nanoparticles with tunable optical properties. So far most scientific efforts have been focused on wide band gap materials to achieve a bright luminescence and a higher solar power conversion efficiency. Their properties in the infrared range of wavelengths are interesting as well. Two strategies can be used to achieve mid-infrared (mid-IR) transition, either interband transition in narrow band gap material or intraband transition in doped material. In this review, we discuss recent progress to achieve stable doped nanocrystals. We focus on mercury chalcogenide compounds since they are so far the only materials that combine mid-IR absorption with photoconductive properties in this range of energies. We discuss the origin of the doping and its tunability as well as how the doping impacts the optical, transport, and photodetection properties. Finally, we discuss Hg-free alternative materials, and present mid-IR transitions.
Highlights
Infrared (IR) technologies remain driven by epitaxially grown materials made of III-V and IIVI semiconductors
The chemistry of nanocrystals enables the receipt of semiconductor nanoparticles with tunable optical properties
Most scientific efforts have been focused on wide band gap materials to achieve a bright luminescence and a higher solar power conversion efficiency
Summary
Infrared (IR) technologies remain driven by epitaxially grown materials made of III-V and IIVI semiconductors. Self-doped nanocrystals of HgS [28,29], HgSe [24,25,30] and HgTe [31,32] started to be synthesized Their absorption spectrum typically presents two contributions: one at high energy (visible and near IR) attributed to interband transition and one in the mid infrared due to an intraband transition, see Fig. 2(b). This decay might be partly balanced by an increase of the absorbance per nanoparticle To date it is not clear rather this emerging intraband/plasmonic colloidal materials have reached a mature level and get limited by fundamental process, we would like to discuss the currently reported results. This makes that the overall detectivity of HgSe intraband photodetectors is one order of magnitude lower than the one currently obtained from HgTe interband CQDs [48], see Fig. 4 (e)
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