Defects in the photocatalysts are among the factors contributing to photocatalytic performance, and they prolong the lifetime of electron-hole pairs via adding trapping states in the band structure. Photoluminescence spectroscopy (PL) is a strong technique to study these phenomena. The PL results record the emission spectra of electrons from high potentials jumping to low potentials . A higher PL intensity might reflect high recombination of electron-hole pairs resulting in inadequate photocatalytic performance.