Advances and Perspectives in Organic Semiconductor‐Based Heterojunctions for Photocatalytic Overall Water Splitting

ABSTRACT Photocatalytic overall water splitting (POWS) is a pivotal technology for sustainable hydrogen energy production. Although numerous semiconductors have been explored, achieving highly efficient POWS with single‐component photocatalyst (whether inorganic or organic) remains challenging due to simultaneous thermodynamic and kinetic demands for the hydrogen evolution reaction and the oxygen evolution reaction. Heterojunction engineering has emerged as a transformative strategy, particularly through organic–organic and organic–inorganic construction, which significantly enhance solar‐to‐hydrogen (STH) efficiency. This review systematically summarizes recent advances in organic semiconductor‐based heterojunctions for POWS, including classical organic–organic and organic–inorganic heterojunctions, as well as novel architectures such as molecular heterojunctions, intramolecular donor–acceptor heterostructures, and intermolecular donor–acceptor assemblies. Beginning with fundamental principles, challenges, and performance indicators, the discussion extends to heterojunction types, interfacial interactions, and structure‐property relationships. Groundbreaking progress is highlighted, followed by an analysis of current challenges and future research directions, aiming to inspire the design of next‐generation high‐performance POWS systems.