The photoluminescence emission spectrum at low temperature of the ${\mathrm{TiO}}_2$ anatase shows a broad band around 2.3 eV that has been largely attributed to self-trapped excitons. In this paper, time-resolved experiments conducted at low temperature on a thin layer and a single crystal give insights into the carrier dynamics inside ${\mathrm{TiO}}_2$. The decay of the photoluminescence with time can be described by a single power law from the picoseconds time range up to the milliseconds time range. The decay rate increases with increasing temperature. We propose to interpret these observations by a collision mechanism between self-trapped excitons that diffuse via hopping processes. These excitons, which are stabilized by the indirect band gap of anatase ${\mathrm{TiO}}_2$, can be ionized at higher temperatures and lead thus to an acceleration of the observed dynamics.

• Received 17 May 2023
• Accepted 11 October 2023

DOI:https://doi.org/10.1103/PhysRevB.108.155204