PbI2 with a unique electronic structure can be synthesized down to the atomic scale by a solution method and used to construct versatile interfacial semiconductors via band alignment engineering. As an illustrative example, the photoluminescence of MoS2 is enhanced due to the type I nature of the MoS2/PbI2 stacks, while dramatic quenching of WS2 and WSe2 occurs in type II WS2/PbI2 and WSe2/PbI2 stacks. Abstract To explore new constituents in two‐dimensional (2D) materials and to combine their best in van der Waals heterostructures is in great demand as being a unique platform to discover new physical phenomena and to design novel functionalities in interface‐based devices. Herein, PbI2 crystals as thin as a few layers are synthesized, particularly through a facile low‐temperature solution approach with crystals of large size, regular shape, different thicknesses, and high yields. As a prototypical demonstration of band engineering of PbI2‐based interfacial semiconductors, PbI2 crystals are assembled with several transition metal dichalcogenide monolayers. The photoluminescence of MoS2 is enhanced in MoS2/PbI2 stacks, while a dramatic photoluminescence quenching of WS2 and WSe2 is revealed in WS2/PbI2 and WSe2/PbI2 stacks. This is attributed to the effective heterojunction formation between PbI2 and these monolayers; type I band alignment in MoS2/PbI2 stacks, where fast‐transferred charge carriers accumulate in MoS2 with high emission efficiency, results in photoluminescence enhancement, and type II in WS2/PbI2 and WSe2/PbI2 stacks, with separated electrons and holes suitable for light harvesting, results in photoluminescence quenching. The results demonstrate that MoS2, WS2, and WSe2 monolayers with similar electronic structures
Published in: "Advanced Materials".