Slow Auger Recombination in Ag<sub>2</sub>Se Colloidal Quantum Dots.

Liao, Chen; Tang, Luping; Jia, Yunzhe; Sun, Shaoling; Yang, Haoran; Xu, Jie; Gu, Zixuan · Nano Lett · 2023

basic_science · Level V

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Abstract

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 Ag<sub>2</sub>Se QDs were studied through transient absorption experiments. As the QD radius increases from 0.9 to 2.5 nm, the biexciton lifetime (τ<sub>2</sub>) of Ag<sub>2</sub>Se 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 (τ<sub>3</sub>) of Ag<sub>2</sub>Se QDs follow <i>R</i><sup>3</sup> and <i>R</i><sup>2.6</sup> dependence, respectively. Moreover, the ratio of τ<sub>2</sub>/τ<sub>3</sub> is ∼2.3-3.2, which is markedly lower than the value expected from statistical scaling (4.5). These findings suggest that environmentally friendly Ag<sub>2</sub>Se QDs can serve as excellent candidates for low-threshold lasers and third-generation photovoltaics utilizing carrier multiplication.