Two-Dimensional Ferroelectric CN/InSe Heterobilayer with Tunable Electronic Property and Photovoltaic Effect.

Two-dimensional ferroelectric monolayer materials with reversible spontaneous polarization provide more regulatory dimensions for their relevant van der Waals heterostructures. Using first-principles calculations, we construct the CN/InSe bilayer heterostructure and study its physical properties as well as the effects of -field and strain. The results indicate that the intrinsic polarization of the component InSe monoalyer can significantly adjust the electronic properties of the CN/InSe heterobilayer. When the polarization of the InSe monolayer points to the interface (up-InSe), the CN/InSe bilayer behaves as the type-I indirect band gap heterostructure, while it transforms to the type-II direct band gap heterostructure after reversing the polarization of the InSe monolayer (dp-InSe). Furthermore, the two CN/InSe heterostructures both have enhanced optical absorption in the visible region than the isolated InSe and CN monolayers. More importantly, the external electric field and strain can easily regulate the electronic properties of the CN/InSe heterostructures. The power conversion efficiency (PCE) of the type-II CN/dp-InSe heterostructure is 8.16%, and the electric field of 0.1 V/Å and the strain of -2% can transform the CN/up-InSe heterostructure into type-II one, conducive to the high PCE up to 24.03 and 24%, respectively. Our proposed CN/InSe heterostructure is promising in future luminescent and photovoltaic fields, and our findings also provide a strategy for functionalizing 2D monolayer materials by the intrinsic polarization property of ferroelectric materials.