  Understanding the physics underlying energy dissipation is necessary for the
effective thermal management of devices based on two-dimensional (2D) materials
and requires insights into the interplay between heat generation and diffusion
in such materials. We review the microscopic mechanisms that govern Joule
heating and energy dissipation processes in 2D materials such as graphene,
black phosphorus and semiconducting transition metal dichalcogenides. We
discuss the processes through which non-equilibrium charge carriers, created
either transiently through photoexcitation or at steady state by a large
electric field, undergo energy relaxation with the lattice and the substrate We
also discuss how these energy dissipation processes are affected by the device
configuration (heterostructure, substrate material including hexagonal boron
nitride, etc) as the use of different substrates, encapsulation, disorder, etc
can introduce or remove scattering processes that change the energy relaxation
pathways. Finally, we discuss how the unique carrier scattering dynamics in
graphene-based vdW heterostructures can be exploited for optoelectronic
applications in light emission and photodetection.
