ZnSe/ZnS Core–Shell Quantum Dots Doped with Mn²⁺ Ions for Magnetic State-Manipulated Light Sources

Spintronic states-associated photoluminescence (PL) is of interest and essential for electronic spin-manipulated information storage and communications. Manganese ions (Mn2+)-doped semiconductor quantum dots (QDs) exhibit a unique PL that comes from the spin-forbidden 4T1–6A1 d–d transition of Mn2+, which is a promising candidate for a spin-manipulated light source. However, the interplay of PL quantum yield (PL QY) and the magnetic states of Mn2+ dopants is still vague. In this work, we systematically investigate the spectroscopic properties of Mn2+-doped ZnSe/ZnS core–shell QDs. By increasing the doping concentration, the PL QY of the Mn2+ dopant is increased to a maximum of 43.2% (2% Mn2+-doped QDs) before decreasing for higher-doped QDs (10% Mn2+-doped QDs). We further found that the high doping in the QDs induces the magnetic coupling of Mn2+ ions, which leads to a larger PL intensity and line-width variation as a function of the temperature from 300 to 80 K. The abnormal PL line-width derivation of high-doped QDs occurs around 150 and 240 K, where would be the Neel temperature of MnS and MnSe, respectively, which allows transition between para-magnetism and anti-ferromagnetism. Our findings of doping-concentration-dependent PL QY and magnetism transition-related PL variation in this work offer a vision for the spintronic states-associated PL of the Mn2+ dopant in the QD host.