Extended Short-Wavelength Infrared Ink by Surface-Tuned Silver Telluride Colloidal Quantum Dots and Their Infrared Photodetection

Wavelength-tunable infrared materials, particularly those excluding regulated substances, are essential for next-generation optoelectronics. Silver telluride (Ag₂Te) colloidal quantum dots (CQDs) can be a promising alternative to traditional Pb- or Cd-based narrow-band gap semiconductors due to their low toxicity. However, the strong binding affinity of thiol ligands has limited the broader use of Ag₂Te CQDs, necessitating more versatile surface chemistries. Here, we synthesized Ag₂Te CQDs passivated with oleylamine, which facilitated various ligand passivation strategies. The weak bonding strength allows the preparation of X-Ag₂Te CQD (X = Cl, Br, or I ligands) inks, sensitive to 1.1-2.7 μm infrared radiation. Using the CQD inks, we fabricated extended short-wavelength infrared (eSWIR) CQD photodiodes with two different sizes of CQDs. The resulting Ag₂Te CQD ink-based eSWIR photodiodes exhibited an external quantum efficiency of 16% at 1.7 μm at room temperature, representing the highest value achieved for nontoxic CQD IR detectors at the wavelength.