Photon emission mechanisms of different phosphors

Abstract

A comparison is made between the different mechanisms involved in the electron and photon excitation processes of four different phosphors. The green luminescence peak of SrAl 2O 4:Eu 2+, Dy 3+ phosphor is normally asymmetrical and tails towards the longer wavelengths. The observed peak in the longer wavelength region is associated with preferential alignment of one of the Eu 2+ d-orbitals. Four Gaussian peaks fitted to the cathodoluminescent (CL) and photoluminescent (PL) spectra of broad band emission spectra of X 1–Y 2SiO 5:Ce phosphor may be attributed to the two different sites (A1 and A2) of the Ce 3+ ion in the host matrix and the difference in orientation of the neighbour ions in the complex crystal structure. Co-activation of Ce 3+ with Eu 3+ quenches the red emission from Eu 3+ and considerably increases the blue emission from Ce 3+ in a SiO 2 matrix. In nanoparticulate PbS the emission data show a blue shift from the normal emission at ∼3200 nm in PbS bulk to ∼560–700 nm. The blue shifting of the emission wavelengths from 3200 to ∼560–700 nm is attributed to quantum confinement of charge carriers in the restricted volume of nanoparticles.