Anion-Driven Bandgap Tuning of AgIn(S x Se 1- x ) 2 Quantum Dots.

Accurate tuning of the electronic and photophysical properties of quantum dots is required to maximize the light conversion efficiencies in semiconductor-assisted processes. Herein, we report a facile synthetic procedure for AgIn(S _x Se _{1- x} ) ₂ quantum dots with S content ( x ) ranging from 1 to 0. This simple approach allowed us to tune the bandgap (2.6-1.9 eV) and extend the absorption of AgIn(S _x Se _{1- x} ) ₂ quantum dots to lower photon energies (near-IR) while maintaining a small QD size (∼5 nm). Ultraviolet spectroscopy studies revealed that the change in the bandgap is modulated by the electronic shifts in both the valence band and the conduction band positions. The negative overall charge of the as-synthesized quantum dots enabled us to make films of quantum dots on mesoscopic TiO ₂ . Excited state studies of the AgIn(S _x Se _{1- x} ) ₂ quantum dot films demonstrated a fast charge injection to TiO ₂ , and the electron transfer rate constant was found to be 1.5-3.5 × 10 ¹¹ s ^-1 . The results of this work present AgIn(S _x Se _{1- x} ) ₂ quantum dots synthesized by the one-step method as a potential candidate for designing light-harvesting assemblies.