Time-related luminescence spectroscopic investigation of electron trapping and recombination in infrared stimulated luminescence

Infrared stimulated luminescence (ISL) occurred in CaS:Eu,Sm due to formation of luminescent centres Eu and electron trapping centres Sm. The electron trapping centres Sm became occupied (forming Sm by trapping excited electrons) in photoluminescence (PL) excitation (PLX) process causing simultaneous ionization of luminescent centres Eu (leaving Eu by losing an electron or capturing a hole). In this paper, the electron trapping in PLX and the recombination in ISL were examined by the time-related PL and ISL spectra of CaS:Eu,Sm. The spectroscopic evidence confirmed that the ISL in CaS:Eu,Sm was produced due to recombination of de-trapped electrons and previously ionized luminescent centres (Eu). It was believed that the electron trapping occurred concurrently as occurrence of the PL of Eu in PLX process. However, the recombination of de-trapped electrons and previously ionized luminescent centres took about 10 {/content/J7B65RQ7FDGJX7JC/xxlarge956.gif}s or even more to occur after infrared irradiation.