Abstract: An emerging TAPA-PDA/ZnIn2 S4 (TP/ZIS) S-scheme heterojunction has been developed to facilitate efficient charge transfer and extend carrier lifetimes, overcoming common challenges faced by single-component photocatalysts. This study employs continuous wave, pulse, and time-resolved electron paramagnetic res-onance (EPR) spectroscopy to identify stable radical defects at the interface and track photoinduced elec-tron transfer from TP to ZIS. This transfer results in the formation of spin-correlated radical pairs, which promote charge separation and minimize recombination. Additionally, femtosecond transient absorption spectroscopy further supports the observation of prolonged carrier lifetimes. By integrating organic and inorganic components, this strategy addresses key issues in heterojunction design and underscores the importance of EPR for revealing charge transfer mechanisms. These results provide valuable insights into the development of efficient, durable photocatalysts, advancing the potential for sustainable solar energy technologies.

Key words: Advanced EPR technology, Interfacial charge transfer, S-scheme heterojunction