An attempt to enhance the afterglow luminescence of NIR light emitting long persistent phosphor ZnGaGeO:Cr by Pr co-doping.

In this study we have focused on the improvement of luminescence intensity and the long afterglow luminescence of Cr doped ZnGaGeO long persistent phosphor by adding an appropriate amount of Pr ions in proportion with Ga concentration. We have successfully developed a series of long persistent ZnGaCrPrGeO (where x = 0, 0.04 and y = 0, 0.01, 0.02, 0.03, 0.04) phosphors by high temperature solid state reaction method. The structural properties of the developed phosphors were characterized by X-ray diffraction method. The diffuse reflectance spectra were recorded at room temperature and it shows three strong absorbance bands at the wavelength of 256, 412 and 570 nm due to the transitions of A→T (4P), A→T (4F) and A→T (4F) of Cr ions which are also confirmed from the photoluminescence (PL) excitation spectra. PL emission analysis revealed that developed phosphors have a strong narrow luminescence around 698 nm and significantly enhanced with the Pr content upto its optimum value (0.02). Afterglow NIR light emission from the developed phosphors was captured by night vision monocular and it is found that the phosphors have long persistent luminescence for more than 24 h. Thermoluminescence (TL) measurement was also carried out for better understanding the kinetic mechanism and luminescence process in these materials. This will enable to calculate the trapping parameters associated with prominent glow peaks.