**Abstract**

2D materials like transition metal dichalcogenides, black phosphorous, silicene, graphene are at the forefront of being the most potent 2D materials for optoelectronic applications because of their exceptional properties. Several application-specific photodetectors based on 2D materials have been designed and manufactured due to a wide range and layer-dependent bandgaps. Different 2D materials stacked together give rise to many surprising electronic and optoelectronic phenomena of the junctions based on 2D materials. This has resulted in a lot of popularity of 2D heterostructures as compared to the original 2D materials. This chapter presents the progress of optoelectronic devices (photodetectors) based on 2D materials and their heterostructures.

**Keywords:** 2D materials, graphene, silicene, TMDCs, responsivity, detectivity, photo-conductive gain
