Understanding charge carrier dynamics in organic photocatalysts for hydrogen evolution

Hydrogen generation using particulate photocatalysts is a promising approach to achieving sustainable energy solutions to energy shortages and environmental challenges. Among them, organic semiconductor-based photocatalysts offer significant advantages, including tunable structural and optoelectronic properties, easy of processibility, and cost-effectiveness over the inorganic photocatalysts. However, their photocatalytic efficiency is limited by inherent properties, such as the formation of Frenkel excitons, the presence of numerous energetic defects, and low charge separation efficiency. To enhance performance and expand the potential of organic photocatalysts, it is crucial to understand the relationship between molecular structure and charge carrier dynamics in photocatalytic processes. In this reason, Recent research about organic photocatalysis for hydrogen evolution has focused on uncovering limiting factors and comprehending the fundamental charge carrier behaviors that determine the performance of organic photocatalysts by utilizing the use of advanced time-resolved analysis tools. This review desicribes charge behaviors, including photocharge generation and transport within the bulk of the organic photocatalyst, as well as charge transfer and charge-induced redox reactions at the interface within photocatalytic system. Their characteristics, according to the molecular structures, are summarized based on time-resolved analysis methodologies, including transient spectroscopy with the aim to provide an understanding of the correlation between charge carrier dynamics, molecular structure, and photocatalytic performance.