Extended Short-Wavelength Infrared Photoluminescence and Photocurrent of Nonstoichiometric Silver Telluride Colloidal Nanocrystals.

Demands on nontoxic nanomaterials in the short-wavelength infrared (SWIR) have rapidly grown over the past decade. Here, we present the nonstoichiometric silver chalcogenide nanocrystals of AgTe ( > 2) and AgTe/AgS CQDs with a tunable bandgap across the SWIR region. When the atomic percent of the metal and chalcogenide elements are varied, the emission frequency of the excitonic peak is successfully extended to 2.7 μm. Surprisingly, the AgTe CQD film responds to the SWIR light with a responsivity of 2.1 A/W at 78 K. Also, the AgS shell growth over the AgTe core enhances not only the emission intensity but also the structural rigidity, preventing crystal morphology deformation under the electron beam. The origin of the enhancement in the emission intensity and air stability of AgTe and AgTe/AgS CQDs is carefully investigated by X-ray photoelectron spectroscopy (XPS). The optical properties and infrared photocurrent of AgTe CQDs will provide new opportunities for solution-based SWIR applications.