Molecular‐Level Modulation of Proton Transport via Electron‐Proton Coupling in Bio‐p‐n Junctions

Integrating biological proton transport with semiconductor photoelectronics offers a powerful route toward next‐generation bioelectronic sensing. Here, a light‐driven bio‐p‐n junction integrating bacteriorhodopsin (bR) with poly(3‐hexylthiophene) (P3HT) is presented. Electron–proton coupling facilitates controlled modulation of bR‐mediated proton transport, leading to a stable and highly linear electronic response along with enhanced interfacial charge separation. Mechanistic analysis reveals that photoexcited electrons from P3HT lower the energy barrier for proton translocation in bR, while pH‐regulated surface charges modulate ion mobility at the interface. This molecular‐level coupling strategy bridges biological specificity with semiconductor scalability, providing a generalizable framework for precise, stable, and biocompatible real‐time pH monitoring in biomedical and environmental applications.