Spin-Enhanced Self-Powered Light Helicity Detecting Based on Vertical WSe₂–CrI₃ <i>p–n</i> 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 <i>p</i>-<i>n</i> 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>I</i>_PH exhibits obvious asymmetry with respect to the bias <i>V</i>, with the <i>I</i>_PH of reversely biased WSe₂-CrI₃ <i>p-n</i> 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>I</i>_SC and <i>I</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.