Spectroscopic and kinetic characterization of photogenerated charge carriers in photocatalysts

The catastrophic consequences of increased power consumption, such as drastically rising CO2 levels, natural disasters, environmental pollution and dependence on fossil fuels supplied by countries with totalitarian regimes, illustrate the urge to develop sustainable technologies for energy generation. Photocatalysis presents eco-friendly means for fuels production via solar-to-chemical energy conversion. The conversion efficiency of a photocatalyst critically depends on charge carrier processes taking place in the ultrafast time regime. Transient absorption spectroscopy (TAS) serves as a perfect tool to track those processes. The spectral and kinetic characterization of charge carriers is indispensable for the elucidation of photocatalytic mechanisms and for the development of new materials. Hence, in this review, we will first present the basics of TAS and subsequently discuss the procedure required for the interpretation of the transient absorption spectra and transient kinetics. The discussion will include specific examples for charge carrier processes occurring in conventional and plasmonic semiconductors.