Dipole‐Manipulated Built‐In Electric Field Enables Ultrafast Charge Separation in Perylene Diimide Polymers for Photoelectrochemical Water Splitting

ABSTRACT Molecular dipole engineering in dendrimeric perylene diimide (PDI) polymers creates powerful built‐in electric fields (BIEFs) that dramatically enhance photoelectrochemical performance. By strategically tuning nitrogen content in aromatic linkers (pyridine, pyrimidine, and 1,3,5‐triazine), the pyridine‐linked C 5 N 1 ‐PDI achieves exceptional photocurrent density (68.7 µA cm − 2 at 1.23 V vs. RHE), outperforming its counterparts by 3.42–229 times. Ultrafast spectroscopy reveals this enhancement originates from sub‐picosecond charge separation and efficient multi‐electron accumulation, while theoretical modeling confirms the critical role of linker polarity in BIEF amplification. This work establishes a fundamental structure‐kinetics relationship for designing high‐performance organic photoelectrodes, providing a versatile strategy for advancing solar energy conversion technologies.