Modulating emission color in Mn-doped ZnS/ZnO microbelts via thermal evaporation process

Typically, the photoluminescence spectra of ZnS nanostructures exhibit a blue emission band and this material is commonly doped with Cu²⁺ ions to produce a green band and with Mn²⁺ ions to yield a yellow-orange band for LEDs applications. In this paper, we exclusively focus on Mn-doped ZnS/ZnO microbelts fabricated by a thermal evaporation method. The presence of the ZnO phase in the microbelts without active oxidation of the samples after synthesis influenced the optical properties of the microbelts. Photoluminescence of the prepared microbelts can be turned from a green to an orange band by changing the ratio between MnCl₂ and ZnS powder. Especially, at a precursor ratio of 0.5:1, the neutral white light encompasses blue, green, and orange bands that appear simultaneously. When the content of MnCl₂ equals that of ZnS powder, a high-value color purity (93.88%) can be achieved for the orange emission. The energy transfer mechanism between the ZnS host lattice, ZnO phase and the Mn²⁺ dopant will also be discussed in detail.