  We present a comprehensive investigation of optical properties in
MoSe$_2$/CrSBr heterostructures, unveiling the presence of localized excitons
represented by a new emission feature, X$^*$. We demonstrate through
temperature- and power-dependent photoluminescence spectroscopy that X$^*$
originates from excitons confined by intrinsic defects within the CrSBr layer.
The valley polarization of X$^*$ and trion peaks displays opposite polarity
under a magnetic field, which closely correlates with the magnetic order of
CrSBr. This is attributed to spin-dependent charge transfer mechanisms across
the heterointerface, supported by density functional theory calculations
revealing a type-II band alignment and spin-polarized band structures.
Furthermore, the strong in-plane anisotropy of CrSBr induces unique
polarization-dependent responses in MoSe$_2$ emissions. Our study highlights
the crucial role of defects in shaping excitonic properties. It offers valuable
insights into spectral-resolved proximity effects in van der Waals
heterostructures between semiconductor and magnet, contributing to advancing
spintronic and valleytronic devices.
