  The unprecedented demand for sophisticated, self-powered, compact, ultrafast,
cost-effective, and broadband light sensors for a myriad of applications has
spurred a lot of research, precipitating in a slew of studies over the last
decade. Apart from the photosensing ability of an active element in the light
sensor, the device architecture is crucial in terms of photoinduced charge
carrier generation and separation. Since the inception of graphene and the
subsequent research growth in the atomically thin 2D materials, researchers
have developed and adapted different families of 2D materials and device
architectures, including single element 2D, 0D/2D, 2D/2D, 1D/ 2D stacked
structures, and so on. This review discusses the recent reports on the
light-sensing properties of various 2D materials, their heterostructures, and
characteristics applicable to the ultraviolet-near infrared (UV-NIR),
short-wave IR (SWIR), mid-wave IR (MWIR), long-wave IR (LWIR), and terahertz
(THz) spectral ranges. It highlights the novelty of the burgeoning field, the
heightened activity at the boundaries of engineering and materials science,
particularly in the generation of charge carriers, their separation, and
extraction, and the increased understanding of the underpinning science through
modern experimental approaches. Devices based on the simultaneous effects of
the pyro-phototronic effect (PPE) and the localized surface plasmon resonance
(LSPR) effect, the photothermoelectric effect (PTE)-assisted photodetectors
(PDs), waveguide-integrated silicon-2D PDs, metal-2D-metal PDs, and organic
material PDs are examined rigorously. Theoretical treatment utilizing various
computational approaches to investigate 2D materials and heterostructures for
photodetection applications is also briefly discussed.
