Tunable White-Light Emission of Co²⁺ and Mn²⁺ Co-Doped ZnS Nanoparticles by Energy Transfer between Dopant Ions

Fabrication of white light-emitting nanophosphors with high luminous efficacy is an urgent need for the next-generation lighting industry and display systems. While rare-earth ions have been frequently utilized as dopants to fabricate semiconducting and dielectric nanophosphors, the limited abundance of rare-earth elements on our planet demands a search for suitable alternatives. Here, we report the fabrication of ZnS nanoparticles co-doped with Co 2+ and Mn 2+ transition metal ions which manifest intense near-white light emission under ultraviolet excitation. While the nanophosphors could be fabricated through a simple low-temperature two-step chemical process, both the color and intensity of their emission can be tuned just by varying the molar concentration of the two dopant ions. The variation of the emission color and its intensity in the nanophosphors due to the dopant ion concentration has been explained considering the interband energy transfer from Mn 2+ ions to Co 2+ ions and creation of deep level defect states in the host nanocrystals. The synthesis process utilized in the present work opens up the possibility of fabricating low-cost, emission-tuned, rare-earth-free nanophosphors for developing high-efficiency light-emitting devices.