Self-powered photodetectors based on two-dimensional van der Waals semiconductors

Self-powered photodetectors (SPPDs) have gained interest in recent years for their potential to be relevant for sustainable and energy-efficient solutions to future optoelectronics. Particularly, two-dimensional (2D) van der Waals (vdW) semiconductor-based SPPDs provide benefits, which are associated with their high responsivity, fast detection speed, as well as their capability of being applicable to flexible, lightweight, and complementary metal-oxide-semiconductor (CMOS)-compatible device applications. Here we review the state-of-the-art SPPDs based on 2D vdW semiconductors utilizing various mechanisms including photovoltaic (PV) effects, piezo-phototronic effects, and bulk photovoltaic effects (BPVEs). In addition to basic device structures, the strategies such as vdW heterostructures and strain engineering are discussed, which represent potential routes to enhance key figure of merits in SPPDs. Finally, we summarize current challenges and future opportunities in 2D SPPDs, providing an insight to deliver practical devices towards high-performance 2D vdW optoelectronics.