Enhancement in green and NIR emissions of Er3+ by energy transfer from ZnSe nanoparticles in borosilicate glass

Borosilicate glass samples singly- and co-doped with Er3+ and ZnSe, were obtained via the melt quenching technique. Structural and morphological characterization confirmed the formation of ZnSe nanoparticles (NPs) during glass preparation. The glassy samples present the characteristic absorption bands of the respective species. Optical band gap values indicate quantum confinement effect in ZnSe-doped glasses. Excitation spectra of the co-doped glasses also display the characteristic bands of both ZnSe and Er3+. Intensity depleted regions at 377 and 521 nm observed in the excitation band of ZnSe indicate absorption by Er3+, that is, energy transfer from the ZnSe NPs to Er3+ ion. Upon excitation at 367, 447 and 498 nm, ZnSe doped glasses give broad emission bands centered around 696 nm. This reveals a broad multiple-band structure due to the overlap of emissions from NPs (electron-hole recombination) and from defect to traps, formed owing to Se and Zn vacancies. The Er3+-doped glasses display green (526 and 550 nm) and NIR (1530 nm) emissions when excited at 377 nm. The co-doped glasses show emission bands of both Er3+ and ZnSe. When compared to ZnSe and Er3+ singly doped glasses, a decrease is observed in the overall red emission while the green and NIR emissions from Er3+ increase. The intensity enhancement of Er3+ emissions increase with increasing ZnSe content which is attributed to the energy transfer from ZnSe NPs to Er3+. It was also observed that the color of the emitted light from the co-doped glasses, changes with change in excitation slit width.