  More is left to do in the field of flat bands besides proposing theoretical
models. One unexplored area is the flat bands featured in the van der Waals
(vdW) materials. Exploring more flat-band material candidates and moving the
promising materials toward applications have been well recognized as the
cornerstones for the next-generation high-efficiency devices. Here, we utilize
a powerful high-throughput tool to screen desired vdW materials based on the
Inorganic Crystal Structure Database. Through layers of filtration, we obtained
861 potential monolayers from 4997 vdW materials. Significantly, it is the
first example to introduce flat-band electronic properties in the vdW materials
and propose three families of representative flat-band materials by mapping
two-dimensional (2D) flat-band lattice models. Unlike existing screening
schemes, a simple, universal rule, i.e., 2D flat-band score criterion, is first
proposed to efficiently identify 229 high-quality flat-band candidates, and
guidance is provided to diagnose the quality of 2D flat bands. All these
efforts to screen experimental available flat-band candidates will certainly
motivate continuing exploration towards the realization of this class of
special materials and their applications in material science.
