Sodium Chloride Protected CdHgTe Quantum Dot Based Solid-State Near-Infrared Luminophore for Light-Emitting Devices and Luminescence Thermometry

Solid-state luminophores operating in the near-infrared (NIR) region may have applications in sensing, communication, and medicine. We report environmentally protected solid-state NIR-emitting luminophores fabricated by embedding CdHgTe colloidal quantum dots (QDs) into a NaCl matrix, with remarkable photo- and thermal stability and a photoluminescence quantum yield of 31% in the solid state, which is among the highest reported for solid-state NIR luminophores so far. We employed this luminophore as a down-conversion layer in a NIR-light-emitting device with a stable emission at 940 nm. Carrier recombination dynamics of the CdHgTe QDs@NaCl powders are examined as a function of temperature using steady-state and transient photoluminescence spectroscopy, and characteristic parameters such as the band gap, the temperature coefficient, the Debye temperature, the activation energy of thermal quenching, and radiative and nonradiative recombination rates are derived. Temperature-dependent changes of the spectral position and the photoluminescence lifetime of CdHgTe QDs@NaCl are shown to serve as a base for two temperature detection schemes, namely, luminescence spectral and luminescence lifetime thermometry, a versatile optical technique for the noninvasive, noncontact estimation of local temperature.