Effects of nanostructure on optoelectronic properties of β phase polyoctylfluorene thin film

► Longer solvent annealing time will lead to more and larger β phase PFO crystallites. ► PL and EL decrease with increasing solvent annealing time. ► Decrease of PL and EL is caused by vacancy defects generated in the crystallization process.► Dipping method will lead to less out-of-plane ordered structure and higher PL. ► Vacancy defects mainly come from the formation of out-of-plane crystalline structure.