2D and quasi-2D hybrid halide perovskite single crystals: From fundamentals to functionalized photodetectors

Distinguished from conventional three-dimensional (3D) organic-inorganic hybrid halide perovskites (OHPs), two-dimensional (2D) and quasi-2D OHP single crystals have attracted increasing research interests due to their unique optoelectronic properties. These materials exhibit a special quantum-well structure featuring an alternating arrangement of insulating organic layers and semiconducting inorganic layers. This arrangement gives rise to notable dielectric and quantum confinement effects, which induce strong electron-phonon coupling, formation of sub-band states, suppressed ion migration and anisotropic charge transport properties, rendering them highly suitable for functionalized photodetectors. These properties have inspired many innovative device designs, such as weak light detection, narrowband detection, self-powered and mechanically flexible devices. This review paper provides an overview of the recent research progress of 2D and quasi-2D OHP single crystals, with the focus on their crystal structure, advanced synthetic methods, intrinsic properties, and applications in photodetectors. We also discuss existing challenges and potential opportunities for future investigations in this research field.