Electron–hole recombination in the bulk of a rutile TiO2 single crystal studied by sub-nanosecond transient absorption spectroscopy

The rate constant of electron–hole recombination in the bulk of a rutile TiO2 single crystal was estimated to be krec = 5 × 10−13 cm−3 s−1 through sub-nanosecond time-resolved transient absorption spectroscopy. This value is more than four orders of magnitude smaller than the diffusion-limited rate constant ( k rec diff = 1.4 × 10 - 8 cm - 3 s - 1 ) for a rutile TiO2 crystal, suggesting low recombination reactivity between electrons and holes in the crystal.