ABSTRACT

Phosphor is a man-made, synthetic substance that exhibits the phenomenon of luminescence under the action of various types of energization, that is, uorescence or phosphorescence. Both these processes result in the emission of photons with wavelength longer than that of the energizing photon, which leads to an energy loss. e dierence in wavelengths/frequencies of the incident and emergent light is known as the Stokes shift. In uorescence, the emission decay takes place over tens of nanoseconds while in phosphorescence, a slow or leisurely withering in brightness (>1 ms) is observed. e afterglow duration for phosphors languishes in the range from 10−6 s to several hours. It is determined by the style of energy transformation and the lifetime of the excited state.