Background: Due to the difference in the numbers of graphene layers, graphene can be classified as Single-Layer Graphene (SLG), Bi-Layer Graphene (BLG), and few-layer graphene. The band gap of SLG is zero, which greatly limits its application to electronic devices.
Objective: Bi-layer graphene (BLG), graphene with two layers, not only possesses most of the advantages of single-layer graphene, but also has some special properties. The opened band gap makes BLG one of the promising materials in the field of electronic devices.
Strategy: The interesting electronic properties of BLG have drawn extensive attention; however, it is still challenging to realize its commercial applications currently due to the limitation in large-scale production and development of advanced applied technologies. Therefore, a timely and deep discussion of BLG is quite necessary.
Review: In this review, the recent progress of BLG is introduced in detail, including the structure, properties and preparation. Then, its potential applications are discussed, involving in ultrafast lithium ion conductors, superconductors, ultrahard carbon films and field-effect transistors, revealing its tremendous prospects. Finally, a summary is given to guide the further study of BLG.