Spin-Enhanced Self-Powered Light Helicity Detecting Based on Vertical WSe₂–CrI₃ p–n Heterojunction

Two-dimensional (2D) magnetic semiconductors offer an intriguing platform for investigating magneto-optoelectronic properties and hold immense potential in developing prospective devices when they are combined with valley electronic materials like 2D transition-metal dichalcogenides. Herein, we report various magneto-optoelectronic response features of the vertical hBN–FLG–CrI₃–WSe₂–FLG–hBN van der Waals heterostructure. Through a sensible layout and exquisite manipulation, an hBN–FLG–CrI₃–FLG–hBN heterostructure was also fabricated on identical CrI₃ and FLGs for better comparison. Our results show that the WSe₂–CrI₃ heterostructure, acting as a p–n heterojunction, has advantageous capability in light detection, especially in self-powered light helicity detecting. In the WSe₂–CrI₃ heterojunction, the absolute value of photocurrent I_PH exhibits obvious asymmetry with respect to the bias V, with the I_PH of reversely biased WSe₂–CrI₃ p–n heterojunction being larger. When the CrI₃ is fully spin-polarized under a 3 T magnetic field, the reversely biased WSe₂–CrI₃ heterojunction exhibits advantageous capability in light helicity detecting. Both the short-circuit currents I_SC and I_PH show one-cycle fluctuation behaviors when the quarter-wave plate rotates 180°, and the corresponding photoresponsivity helicities can be as high as 18.0% and 20.1%, respectively. We attribute the spin-enhanced photovoltaic effect in the WSe₂–CrI₃ heterojunction and its contribution to circularly polarized light detection to the coordination function of the spin-filter CrI₃, the valley electronic monolayer WSe₂, and the spin-dependent charge transfer between them. Our work helps us understand the interplay between the magnetic and optoelectronic properties of WSe₂–CrI₃ heterojunctions and promotes the developing progress of prospective 2D spin optoelectronic devices.