2PC measurements of the intrinsic response time may also be used to explore the potential of more complicated TMDC device structures, such as vertical van der Waals p-n junction heterostructures. The strong built-in electric field in these junctions has been shown to greatly reduce the carrier drift time. This mitigates the detrimental effect of thick multilayers (see the example of MoTe2 in Figure ) and allows exploiting the larger total absorbance of bulk crystals.