Mid-Infrared Intraband Transition of Metal Excess Colloidal Ag₂Se Nanocrystals

Steady-state intraband transition, which is a promising electronic transition of a colloidal quantum dot along with the band-gap transition, had been a long-standing challenge. The steady-state intraband transition occurring between discrete electronic states in the conduction band of a colloidal nanocrystal has been reported only from mercury chalcogenide nanocrystals for the past few years. Concerns about the toxicity of the mercury compound necessitate a new nontoxic system exhibiting a steady-state intraband transition. Here we present the steady-state intraband absorption and photoluminescence of Ag₂Se colloidal nanocrystals under ambient conditions. The mid-IR intraband transition is carefully investigated by means of FT-IR emission spectroscopy, spectroelectrochemistry, compositional analysis, and transfer characteristics. Especially, the mid-IR intraband photoluminescence of the Ag₂Se colloidal nanocrystal will open new avenues in the use of quantum-confined colloidal systems for mid- and long-wavelength infrared light sources along with the band-gap transition that has been investigated for the last three decades.