Two‐dimensional (2D) magnetic semiconductors are considered to have great application prospects in spintronic logic devices, memory devices, and photodetectors, due to their unique structures and outstanding physical properties in 2D confinement. Understanding the influence of magnetism on optical/optoelectronic properties of 2D magnetic semiconductors is a significant issue for constructing multifunctional electronic devices and implementing sophisticated functions. Herein, the influence of spin ordering and magnons on the optical/optoelectronic properties of 2D magnetic semiconductor α ‐MnSe synthesized by space‐confined chemical vapor deposition (CVD) is explored systematically. The spin‐ordering‐induced magnetic phase transition triggers temperature‐dependent photoluminescence spectra to produce a huge transition at Néel temperature ( T N ≈ 160 K). The magnons‐ and defects‐induced emissions are the primary luminescence path below T N and direct internal 4 a T 1g → 6 A 1g transition‐induced emissions are the main luminescence path above T N . Additionally, the magnons and defect structures endow 2D α ‐MnSe with a broadband luminescence from 550 to 880 nm, and an ultraviolet–near‐infrared photoresponse from 365 to 808 nm. Moreover, the device also demonstrates improved photodetection performance at 80 K, possibly influenced by spin ordering and trap states associated with defects. These above findings indicate that 2D magnetic semiconductor α ‐MnSe provides an excellent platform for magneto‐optical and magneto‐optoelectronic research.

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