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.