Facile Polymer-Assisted Assembly of Fullerenes into Ultrathin Crystalline Nanosheets with Enhanced Electron Transport...

Ordered assembly of fullerenes is of significant importance in organic electronic applications, as charge carrier mobility in fullerene-based materials is highly sensitive to structural order. However, commonly employed solution-processing techniques often suffer from strong aggregation tendencies or uncontrolled crystallization of fullerenes during film formation. In contrast, advanced nanofabrication techniques that enable precise control over fullerene morphology at the nanoscale are typically complex and costly. In this work, we propose a facile supramolecular strategy based on the polymer-assisted assembly of a pyridinium-functionalized fullerene amphiphile (FPy) to achieve ordered fullerene architectures, thereby enhancing charge carrier mobility through reduced energetic disorder. A commercially available anionic polymer, polystyrenesulfonate (PSS), was employed to assemble the cationic fullerene derivative (FPy) primarily via electrostatic interactions, further stabilized by π-π stacking between fullerene units. The interaction of FPy with PSS was confirmed by UV-visible absorption spectroscopy, while TEM, SEM, and AFM analyses revealed the formation of ultrathin two-dimensional crystalline nanosheets with highly ordered fullerene packing. X-ray diffraction (XRD) analyses clearly demonstrate a transition from polycrystalline FPy to a highly ordered and uniform face-centered cubic (FCC) lattice in the PSS/FPy hybrid, confirming the anionic polymer-induced switching toward a more ordered nanoassembly. Space-charge-limited current (SCLC) measurements further revealed an order-of-magnitude enhancement in electron mobility (0.92 × 10^-3 cm² V^-1 S^-1) compared to FPy alone, which can be correlated with the reduced energetic disorder in the FCC lattice structure of the PSS/FPy hybrid assembly. Overall, this study highlights the significance of polymer-assisted assembly of rationally designed amphiphilic fullerenes as a general and scalable strategy to improve electron transport in a wide range of optoelectronic devices.