Generating and Capturing Secondary Hot Carriers in Monolayer Tungsten Dichalcogenides

It remains challenging to capture and investigate the drift dynamics of primary hot carriers because of their ultrashort lifetime (∼200 fs). Here we report a new mechanism for secondary hot carrier (∼25 ps) generation in monolayer transition metal dichalcogenides such as WS₂ and WSe₂, triggered by the Auger recombination of trions and biexcitons. Using ultrafast photocurrent spectroscopy, we measured and characterized the photocurrent stemming from the Auger recombination of trions and biexcitons in WS₂ and WSe₂. A mobility of 0.24 cm² V^-1 s^-1 and a drift length of ∼3.8 nm were found for the secondary hot carriers in WS₂. By leveraging interactions between exciton complexes, we envision a new mechanism for generating and controlling hot carriers, which could lead to efficient devices in photophysics, photochemistry, and photosynthesis.