Pure red luminescence and concentration-dependent tunable emission color from europium-doped zinc sulfide nanoparticles

Tuning the Red Emission to Instigate Intrinsic White‐Light Emission in Single‐Phase Phosphor with Excellent Color Rendering Index

“…This is possibly because of the fact that the energy is transferred efficiently from one copper to another copper through the non‐radiative transition. Therefore, the quenching of red emission is attributed to the presence of Cu 2+ pairs at a higher doping concentration of Cu 2+ [29] . Subsequently, with an increase in doping concentration green emission is also quenched due to the unavailability of V s and V Zn defects states (– which are responsible for green emission in the host) and due to the unavailability of t 2 for recombination of an electron from conduction band due to Cu−Cu pair formation as stated above [29] .…”

“…Therefore, we have deconvoluted the emission spectrum of doped materials e.g ZSC‐3 and it reasonably yielded three bands at 485 nm, 510 nm, and 700 nm. The blue emission is due to the relaxation of the electron from V S to VB (∼485 nm) [29,30,48–52] Whereas, the emission in the green region (510 nm) can be explained by the radiative relaxation from CB to t 2 energy level (upon doping of Cu 2+ ion to ZnS lattice the energy level of Cu 2+ ion split into lower energy e level and higher energy t 2 level) of Cu dopant [30,49] . The red emission is seen due to the recombination of electrons in the deep localized defect states (that are mainly due to sulphur vacancy) to t 2 of Cu.…”

“…It is worth noting that the red emission observed is even extended further to the near‐infrared (NIR) region beyond 800 nm. The red emission extending to the near‐infrared region is rarely observed in Cu 2+ ‐doped‐ZnS phosphors [29,52] …”

“…With further increase in the Cu 2+ concentration, the quenching of red emission is observed. As the concentration of Cu 2+ increases, the formation of Cu 2+ pair leads to emission quenching [29] . This is possibly because of the fact that the energy is transferred efficiently from one copper to another copper through the non‐radiative transition.…”

“…To tune this, a variety of dopant metal ions and defect engineering have been used to broaden the emission over the visible spectral range [14–24] . Recently, more precise efforts have been made to dope the ZnS lattice with the copper ion (Cu 2+ ) extensively [25–39] . The Cu 2+ ‐doping not only affects the blue luminescence of ZnS, but triggers green and red emissions by generating suitable defect states.…”