From C60Ph5Cl to C60Ph6: complete phenylation of C60 derivative renders superior organic photovoltaic performanceElectronic supplementary information (ESI) available. CCDC 1009636. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c8tc05027a

Fully phenylated C 60 Ph 6 has never been synthesized in the past two decades largely due to steric effect and poor thermodynamic stability of the initial intermediate towards its isostructural penta-phenyl adduct (C 60 Ph 5 X) that has one central site intact. Herein, we report a kinetic management strategy using nitrobenzene that can efficiently alleviate the steric effect in the substitution reaction of C 60 Cl 6 to synthesize C 60 Ph 6 . As revealed by X-ray crystallography, the molecule of C 60 Ph 6 , in stark contrast to its isostructural C 60 Ph 5 Cl with the last chlorine intact, shows a favorable geometrical structure and molecular stacking for electron transport. Furthermore, C 60 Ph 6 shows high LUMO energy of −3.51 eV (0.4 eV higher than that of [6,6]-phenyl-C 61 -butyric acid methyl ester, PCBM), which is promising high open-circuit voltage for organic solar cells. The merits of both molecular packing and electrochemical property of C 60 Ph 6 lead to high open-circuit voltage of 1.04 V for the OSC device based on poly(3-hexylthiophene) (P3HT). The present C 60 Ph 6 exemplifies a novel class of electronic acceptors with fully aromatized groups on a fullerene cage. The fully phenylated C 60 derivative C 60 Ph 6 for organic solar cells with high open-circuit voltage of 1.04 V.