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.