Herein, the structure of an o-xylene C-60 monoadduct (OXCMA) having high electron mobility in solution-processed devices was studied by single-crystal X-ray analysis. The crystal of OXCMA showed a well-aligned three-dimensional network of the C-60 moiety without inclusion of solvent molecules. Density functional theory (DFT) methods and hopping modeling were employed to calculate the charge carrier mobility of OXCMA with good agreement with the experimental mobility.