Promoting Noncovalent Intermolecular Interactions Using a C₆₀ Core Particle in Aqueous PC60s-Covered Colloids for Ultraefficient Photoinduced Particle Activity

Noncovalent intermolecular interactions in nanomaterials, such as van der Waals effects, allow adjustment of the nanoscopic size of compounds and their conformation in molecular crystal regimes. These strong interactions permit small particle sizes to be maintained as the crystals grow. In particular, these effects can be leveraged in the confined/reinforcing phase of molecules. With this in mind, we used C₆₀ molecules as a core particle in single-PC60 surfactant-covered colloid in a water-processable system. Compared with our previous results based on a PC₆₁BM core–PC60 shell particle, the PC60-C₆₀ colloid had a considerably smaller spherical structure due to the increased intermolecular interactions between C₆₀ (fullerene) molecules. Interestingly, the conformation of C₆₀ aggregates was altered depending on the mixed solvents and their volume fraction in the organic phase, which strongly affected the structural properties of the PC60-C₆₀ colloids. The particle facilitated strong interactions with a p-type core sphere when it was introduced as the shell part of a p–n heterojunction particle. This direct interaction provided effective electronic communication between p- and n-type particles, resulting in ultraefficient photonic properties, particularly in charge separation in aqueous heterostructured colloids. This enabled the development of an extremely efficient photovoltaic device with a 6.74% efficiency, which could provide the basis for creating high-performance water-processable solar cells based on p–n heterostructured NPs.