Defect States and Polarons in Photocatalytic Semiconductors Revealed via Time-Resolved Spectroscopy

Defect states and polarons of photocatalytic semiconductors play important roles by notably influencing carrier mobility and reactivity. Extensive studies have focused on identifying defect states and the physical properties of polarons, as well as their consequential impact on catalytic efficiency. This Featured Article summarizes recent investigations of defects and polarons using time-resolved spectroscopies in photocatalytic semiconductors. These include transient infrared absorption–excitation energy scanning spectroscopy to identify defect states within the bandgap of photocatalytic materials such as anatase and rutile TiO2, ZnO, and CdS and time-resolved spectroscopic studies on the temporal evolution of photogenerated electron and hole polarons within these semiconductors. Finally, we address the current challenges in the study of defects and polarons.