Natural Photosensitizer for Regulating Organic Solar Cells: Coupling Mechanisms of Intermolecular Interactions and Energy-Charge Transfer

With the expanding application of eco-friendly natural photosensitizers in photovoltaics, thoroughly investigating energy and charge transfer mechanisms is crucial for enhancing the performance of chlorophyll-based devices. Here, we employed quantum chemistry and spectroscopy to explore hybrid systems comprising a sodium zinc chlorophyll (SZC) donor paired with nonfullerene acceptors in various configurations. The L8-BO acceptor demonstrated superior energy level alignment, complementary light absorption, and larger electrostatic potential differences when interacting with SZC, thereby strengthening intermolecular interactions and improving optoelectronic performance. Steady-state optical studies revealed the synergistic effects of approximately 80% charge transfer along with auxiliary fluorescence resonance energy transfer within SZC-based systems. Optimized 1:1.5 blend films distinguishably exhibit substantial quenching and improved charge transfer. Notably, the superior charge transfer proportion and exciton dissociation efficiency observed in the SZC:L8-BO system were mainly attributed to favorable stacking morphology, enhanced van der Waals forces, abundant charge transfer states, and an ultrafast charge separation rate (up to 2.810 × 10¹⁴ s^-1). This study elucidates the structure-property relationships and interaction mechanisms inherent in chlorophyll-based photoactive layers, thus establishing a foundation for developing high-efficiency organic solar cells.