  Size- and shape- dependent unique properties of the metal halide perovskite
nanocrystals make them promising building blocks for constructing various
electronic and optoelectronic devices. These unique properties together with
their easy colloidal synthesis render them efficient nanoscale functional
components for multiple applications ranging from light emission devices to
energy conversion and storage devices. Recently, two-dimensional (2D) metal
halide perovskites in the form of nanosheets (NSs) or nanoplatelets (NPls) are
being intensively studied due to their promising 2D geometry which is more
compatible with the conventional electronic and optoelectronic device
structures where film-like components are employed. In particular, 2D
perovskites exhibit unique thickness-dependent properties due to the strong
quantum confinement effect, while enabling the bandgap tuning in a wide
spectral range. In this review the synthesis procedures of 2D perovskite
nanostructures will be summarized, while the application-related properties
together with the corresponding applications will be extensively discussed. In
addition, perovskite nanocrystals/2D material heterostructures will be reviewed
in detail. Finally, the wide application range of the 2D perovskite-based
structures developed to date, including pure perovskites and their
heterostructures, will be presented while the improved synergetic properties of
the multifunctional materials will be discussed in a comprehensive way.
