Interfacial Charge Dynamics and Optical Constraints in Chlorophyll-Functionalized TiO2 Nanotube Arrays

초록

Natural pigments offer promise for visible-light harvesting, but their exciton transport and photostability remain limiting factors. Here, we present a biohybrid photoelectrode comprising chlorophyll (Chl) immobilized onto anodized TiO2 nanotube (TNT) arrays. Controlled deposition yields a hierarchical trilayer structure featuring capillary-driven infiltration and tunable optical thickness. Transient photocurrent measurements reveal a synergistic regime in which moderate Chl loading and optimal illumination maximize charge generation. Spectral and time-resolved analyses indicate that exciton quenching occurs via energy delocalization and interfacial electron injection. In contrast, excessive loading leads to exciton confinement, self-shading, and trap-assisted recombination, which collectively suppress charge extraction. These results delineate a design window in which light absorption, exciton mobility, and photostability are cooptimized, offering practical guidance for integrating natural pigments into photoelectrochemical (PEC) systems.

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