HgTe nanocrystals were synthesized with capping ligand mixtures of oleylamine (OAm), trioctylphosphine (TOP), trioctylphosphine oxide (TOPO), and LiN(SiMe<sub>3</sub>)<sub>2</sub> with mid-wavelength infrared (MWIR) light absorption. These nanocrystals were deposited into films on electronic device structures to measure their optical photoresponse. Efficient charge carrier transport in nanocrystal films is typically limited by long chain ligands and necessitates ligand exchange with small molecules to enable increased electronic interparticle coupling. These post-deposition surface treatments often generate surface traps and surface reactive sites that can reduce photoresponse and lead to rapidly degraded device performance over time.  We found that these HgTe nanocrystals with mixed ligand passivation did not require ligand exchange in order to achieve strong photoresponse, and furthermore, that the nanocrystal film photoresponse was stable for at least more than six months.  The optoelectronic properties of the HgTe nanocrystals were evaluated by spectral responsivity, temperature-dependent field effect mobility, and temperature-dependent photocarrier lifetime. To further demonstrate their long-term stability, 8-month-old HgTe nanocrystals were deposited into photodetector structures and exhibited stable MWIR imaging capability.

Stable and photosensitive HgTe colloidal quantum dots

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