Temperature-dependent vacuum ultraviolet photoluminescence spectroscopy of transition metal and rare earth co-doped ZnO phosphors: a synchrotron-based investigation

The synchrotron-based vacuum ultraviolet (VUV) emission spectra of (Fe, Sm) co-doped ZnO phosphors exhibit broad emission in the visible-near infrared region in the temperature range of 10–300 K. These emission spectra are due to the deep defect levels in the host ZnO. Upon codoping of Fe and Sm ions, an efficient energy transfer (ET) from ZnO to Sm 3+ via Fe 2+ /Fe 3+ states occurs. A mechanism explaining the ET resulting due to the involvement of additional energy levels corresponding to Fe 2+ /Fe 3+ and Sm 3+ ions is proposed. The probability of phonon-assisted non-radiative transitions increases at elevated temperatures. In the case of Zn 0.997 Sm 0.025 Fe 0.005 O, the CIE color coordinates shift from orange to blue to white at low temperature with an acceptable Color Rendering Index and Color Quality Scale values, under the VUV excitations. The broadening of emission spectra due to strong electron–phonon coupling at high-temperature resulting in high CRI and CQS values reveals that (Fe, Sm) co-doped ZnO phosphors are suitable materials to use in the detection of space events, plasma display devices, field emission displays, etc.