Dual-functional Cr3+-doped InP quantum dots with pure blue emission and room-temperature ferromagnetism

Indium phosphide (InP) quantum dots (QDs) have gained global research focus owing to their eco-friendly properties and outstanding optical characteristics. However, blue emission of InP QDs has made slow progress owing to surface defects and lattice mismatch between core and shell. Meanwhile, the ferromagnetism of traditional dilute magnetic semiconductors (DMSs) is limited by insufficient Curie temperature, failing to meet practical applications. Herein, we report Cr 3+ -doped InP/ZnS QDs with dual functions of pure blue emission and room-temperature ferromagnetism. By using hot injection method, Cr 3+ ions are precisely embedded into the core-shell interface of QDs, effectively passivating the surface defects of the InP cores. This approach enables the fabrication of pure blue-emitting QDs with an emission of 471 nm, a photoluminescence quantum yield (PLQY) of 52%, and a full width at half maximum (FWHM) of 46 nm. Through the dominance of ferromagnetic superexchange interaction, synergizing with the intrinsic strong local magnetic moment of Cr 3+ and quantum confinement effect, room-temperature ferromagnetism is achieved in InP-based QDs for the first time (Curie temperature above 350 K and maximum coercivity of 95.45 Oe). This work provides new materials for spintronic devices, and the Cr 3+ doping strategy also offers a reference for the opto-magnetic regulation of III-V QDs.