“…Referring to Table , both experiments (PL, PES, XPS, UPS, RPS, XAS) and calculations (DFT, e.g. LDA, GGA+U, B3LYP, sX, HSE06) agree at least that the defects in TiO 2 , which are located around 1 eV below the CB, are Ti 3+ -type ,,,, and show d–d transitions/3d-character and an EPR signal of paramagnetic Ti 3+ . , Measured peaks suffer from ∼0.5 eV fwhm, with the maximum mostly between 0.5 and 1.7 eV, ,,,,,,− so the defects in TiO 2 can be caused either by oxygen vacancies (V O ) or Ti interstitials (Ti int ), and titania layers could correspondingly be a reduced form of TiO 2 , i.e., an O-poor TiO 2– x or a Ti-poor Ti 1– x O 2 . Since consecutively distinguishing between those two defect types experimentally by localizing them in the band gap, the debate on the nature of defects in TiO 2 , found in the references of this paragraph, still goes on.…”