Influence of Polydopamine as a Green Passivating Layer on Organic-Based Photoelectrodes via Ex Situ Transfer

Abstract Photoelectrochemical (PEC) water splitting for renewable fuel production has recently witnessed remarkable progress. Organic semiconductor photoanodes stand at the forefront due to their numerous advantages, such as a wide absorption coefficient, tunable energy levels, and solution processability. However, their stability remains a significant challenge. This study investigates the influence of an eco-friendly hole transport layer, polydopamine (PDA), transferred ex situ onto an organic-based photoanode as a passivating layer. We leverage PDA's unique electrochemical properties as a green and versatile polymer to enhance the stability of the photoanode. Electrochemical tests show that simple ex situ transfer of PDA onto the photoanode surface increases the photocurrent tenfold, reduces the charge transfer resistance from 4.2 to 1.8 kΩ (in the dark) and from 3.5 to 0.4 kΩ (under illumination), while the estimated Fermi energy level shifts by –0.14 eV. These findings support the use of ex situ-transferred PDA as a multifunctional interfacial layer capable of improving charge extraction and photoelectrode stability in organic photoelectrochemical water-splitting systems.