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 WS 2 and WSe 2 , 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 WS 2 and WSe 2 . A mobility of 0.24 cm 2 V -1 s -1 and a drift length of ∼3.8 nm were found for the secondary hot carriers in WS 2 . 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.