2D metal halide perovskites (MHPs), mainly the studied
Ruddlesden–Popper
(RP) and Dion–Jacobson (DJ) phases, have gained enormous popularity
as optoelectronic materials owing to their self-assembled multiple
quantum well structures, tunable semiconducting properties, and improved
structural stability compared to their bulk 3D counterparts. The performance
of polycrystalline thin film devices is limited due to the formation
of defects and trap states. However, as studied so far, single crystal-based
devices can provide a better platform to improve device performance
and investigate their fundamental properties more reliably. This Review
provides the first comprehensive report on the emerging field of RP
and DJ perovskite single crystals and their use in visible light photodetectors
of varied device configurations. This Review structurally summarizes
the 2D MHP single crystal growth methods and the parameters that control
the crystal growth process. In addition, the characterization techniques
used to investigate their crystal properties are discussed. The review
further provides detailed insights into the working mechanisms as
well as the operational performance of 2D MHP single crystal photodetector
devices. In the end, to outline the present status and future directions,
this Review provides a forward-looking perspective concerning the
technical challenges and bottlenecks associated with the developing
field of RP and DJ perovskite single crystals. Therefore, this timely
review will provide a detailed overview of the fast-growing field
of 2D MHP single crystal-based photodetectors as well as ignite new
concepts for a wide range of applications including solar cells, photocatalysts,
solar H2 production, neuromorphic bioelectronics, memory
devices, etc.