Aromatic Connectivity Governs Aggregation and Morphology in Ternary Organic Solar Cells

Why It Matters

Precise control of aggregation and morphology directly lifts efficiency, making ternary organic solar cells more competitive with silicon and expanding their commercial viability.

Key Takeaways

• C1 phenyl linkage reduces self‑aggregation, enabling balanced molecular packing
• C2 thiophene linkage causes coplanar backbone and over‑crystallization
• PM6:Y6:C1 ternary device reaches 77.9% fill factor, 17.98% efficiency
• Optimized interpenetrating network improves in‑plane charge transport
• Aromatic connectivity emerges as a design lever for high‑performance TOSCs

Pulse Analysis

The quest for higher efficiency in organic photovoltaics often hinges on mastering nanoscale morphology. In this study, the researchers leveraged aromatic connectivity—specifically phenyl versus thiophene linkers—to modulate steric torsion and π–π stacking in two donor molecules, C1 and C2. By introducing a phenyl bridge, C1 gains a twisted geometry that suppresses runaway crystallization, creating a more isotropic network that blends well with the acceptor Y6. Conversely, the thiophene bridge in C2 enforces planarity, driving tight face‑on stacking that can impede charge separation when over‑crystallized.

Morphology control translates directly into charge‑transport pathways. The C1‑based ternary blend forms finer interpenetrating domains, redistributing π–π interactions to favor both in‑plane and out‑of‑plane transport. This balanced network reduces recombination losses and aligns energy levels for efficient exciton dissociation. The resulting device delivers a striking 77.9% fill factor and 17.98% power conversion efficiency—metrics that eclipse conventional binary PM6:Y6 cells and the C2‑based ternary counterpart. Such performance underscores how subtle molecular tweaks can yield outsized gains in photovoltaic output.

Beyond the immediate efficiency boost, the findings signal a broader design paradigm for organic solar cells. Aromatic connectivity offers a scalable, chemistry‑driven lever to fine‑tune aggregation without resorting to complex processing steps. As the industry seeks cost‑effective, flexible alternatives to silicon, the ability to engineer morphology at the molecular level could accelerate commercialization of high‑performance, lightweight solar modules. Future work will likely explore other aromatic linkers and donor‑acceptor combinations, expanding the toolkit for next‑generation organic photovoltaics.