Slow Auger Recombination in Ag₂Se Colloidal Quantum Dots

Efficient Auger recombination (AR) presents a significant challenge for the advancement of colloidal quantum dot (QD)-based devices involving multiexcitons. Here, the AR dynamics of near-infrared Ag₂Se QDs were studied through transient absorption experiments. As the QD radius increases from 0.9 to 2.5 nm, the biexciton lifetime (τ₂) of Ag₂Se QDs increases from 35 to 736 ps, which is approximately 10 times longer than that of comparable-sized CdSe and PbSe QDs. A qualitative analysis based on observables indicates that the slow Auger rate is primarily attributed to the low density of the final states. The biexciton lifetime and triexciton lifetime (τ₃) of Ag₂Se QDs follow R³ and R^2.6 dependence, respectively. Moreover, the ratio of τ₂/τ₃ is ∼2.3-3.2, which is markedly lower than the value expected from statistical scaling (4.5). These findings suggest that environmentally friendly Ag₂Se QDs can serve as excellent candidates for low-threshold lasers and third-generation photovoltaics utilizing carrier multiplication.