Band gap modulation and photoelectric properties of two-dimensional CrI3 nanosheets: A first-principles study

Two-dimensional (2D) ferromagnetic materials have emerged as one of the hotspots of research in recent years due to their potential applications in magnetic storage and spintronics. In this paper, the electronic structure and optical properties of CrI3 monolayer (ML) are studied by first-principles calculations. CrI3 ML is a 2D direct bandgap semiconductor with unique magnetic and electronic properties. Biaxial strain and an external electric field can effectively regulate the physical properties of CrI3. The results indicate that under biaxial tensile strain, the band gap decreases with increasing strain and gradually smooths out. When an external electric field is applied, the band gap of the CrI3 ML gradually decreases as the electric field increases, until it transforms into a metallic property at 0.7 V/angstrom or above. Following that, the optical absorption of CrI3 under biaxial strain was investigated. Under tensile and compressive strain, the optical absorption peak appeared redshifted in the visible region. In addition, we also designed a nanodevice based on CrI3 ML to analyze the strain-induced photocon-ductivity changes. It is observed that the biaxial compressive strain on both the edges of the horizontal and vertical directions can redshift the peak photoconductivity, which means that there is a strong photoelectric response to the red, orange, and green visible regions. Our research will expand the applications of CrI3 ML in spintronics and optical electronics.