Intrinsically Conductive Films of Ag2Te Nanocrystals for Broadband Infrared Photodetection beyond 2000 nm

We report a rapid, up-scalable synthesis in an aprotic solvent to obtain Ag2Te nanocrystals that are intrinsically capped with a short, conductive thiol ligand, making them suitable for optoelectronic applications. The simultaneous use of labile and stable tellurium precursors controlled the reaction kinetics and enabled growth of nonbranched, highly crystalline Ag2Te nanocrystals, with well pronounced excitonic peaks and an absorption edge extending beyond 2000 nm. We also realized synthesis of either n-type or p-type Ag2Te nanocrystals by simply tuning their stoichiometry. Using Ag2Te nanocrystal inks, we fabricated infrared photodetectors in a phototransistor configuration, with a high responsivity above 2 A/W and a specific detectivity under broadband illumination reaching 1011 Jones at 160 K, and rise and fall times of 50 and 80 μs, fast enough to resolve kilohertz-scale optical modulation. Our study encourages development of heavy-metal-free nanocrystals for infrared optoelectronic devices operating at temperatures accessible to commercial Peltier coolers.