Photon emission mechanisms of different phosphors

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 SrAl2O4:Eu2+, Dy3+ 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 Eu2+ d-orbitals. Four Gaussian peaks fitted to the cathodoluminescent (CL) and photoluminescent (PL) spectra of broad band emission spectra of X1–Y2SiO5:Ce phosphor may be attributed to the two different sites (A1 and A2) of the Ce3+ ion in the host matrix and the difference in orientation of the neighbour ions in the complex crystal structure. Co-activation of Ce3+ with Eu3+ quenches the red emission from Eu3+ and considerably increases the blue emission from Ce3+ in a SiO2 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.