Intermediate-mediated anion tuning of AgIn(S,Te)2 nanorods for highly efficient NIR-II photoluminescence

Abstract

Ag-In-Te-based nanocrystals are promising non-toxic emitters for near-infrared-II (NIR-II) photoluminescence (PL), but their efficiency is limited by poor surface passivation and the resulting nonradiative recombination. Here, we report an intermediate-mediated synthesis of anion-tuned AgIn(S,Te)2 nanorods. Ag-In-Sx intermediates serve as reactive precursors, enabling S/Te anion tuning during Te-mediated nanorod growth. The photoluminescence quantum yield (PLQY) tracks the residual sulfide retained within the nanorods and is maximized not under the most Te-rich condition, but at an intermediate composition of 66 at% Te and 34 at% S. The retained sulfide is proposed to form local wide-bandgap Ag-In-S-like environments that may contribute to the suppression of nonradiative recombination while preserving NIR-II emission. The optimized pristine nanorods reach a PLQY of 40.2%, which increases to 62.0% after ZnS surface passivation. The AgIn(S,Te)2@ZnS nanorods were further integrated as the photoactive layer in a photodiode device, showing a distinct NIR photoresponse at wavelengths above 800 nm. These results establish Ag-In-Sx intermediate chemistry as an effective route to control anion composition and enhance NIR-II PL in Te-based nanocrystals.