To understand the provenance of these two components, we first analyze the fast component. By studying its dependence on the external bias and temperature, we test our previous hypothesis from the 2PC experiment that this component originates from cooling of injected hot carriers (Figure and). Varying the external voltage from 0.5 V to 3.5 V has no significant effect on the response time, which argues against a transport-related mechanisms , such as charge carrier drift. The negative correlation with temperature, e.g. the observed increase of the lifetime from 3 ps to 5.2 ps while decreasing the temperature from 300 K to 80 K, rules out a recombination-related process 7 . We argue that this phenomenon is best explained with phonon-mediated cooling, where additional energy is needed to activate phonons at low temperature, which slows the cooling . It should be noted that the energy of the input laser (0.795 eV) is smaller than half the bandgap energy of thin layered WS2 (~ 0.96 eV).