Zinc halide enables highly monodisperse Ag2Te colloidal quantum dots for short-wave infrared photodetectors

Ag2Te colloidal quantum dots (CQDs) with superior optoelectronic properties are promising candidates for shortwave infrared photodetectors. Their performance, however, is influenced by their size distribution and structural quality. The most widely used method for synthesizing Ag2Te CQDs employs phosphine-tellurium as a precursor. Phosphine, however, is suspected to affect the film's electrical conductivity, thereby rendering device performance. Recently, a phosphine-free synthesis approach for Ag2Te CQDs has been developed. This method requires continuous injection and growth routes to achieve absorption peaks greater than 1600 nm, and the surface passivation needs further refinement. To address these challenges, we propose a zinc halide (ZnX2)-controlled method that reduces precursor reactivity by forming complexes of Ag-X. This facilitates the growth of uniformly sized CQDs through a one-step hot injection process, resulting in nearly monodispersed CQDs with tunable optical bandgaps from 1.22 to 0.60 eV. This method also improves surface passivation due to Zn2 + incorporation in synthesis. Utilizing these Ag2Te CQDs, we fabricated infrared photodetectors that demonstrate a responsivity of 0.38 A W-1 and an external quantum efficiency of 30 % at 1550 nm, positioning them among the best-performing CQD photodetectors.