Analysis and control of energy transfer processes and luminescence across the visible spectrum in PFO:P3OT blends

A systematic study of luminescence from blends made of poly (9, 9-dioctylfluorene-2, 7-diyl) (PFO) and poly (3-octylthiophene-2, 5-diyl) (P3OT), and its photophysics was carried out. Acceptor concentration influence and sample preparation conditions was analyzed, particularly regarding the solvent, in order to control emission through the entire visible spectrum, and to understand the physical processes involved. An additional emission band observed in PFO:P3OT films with low concentration of P3OT was studied through confocal luminescence microscopy and was attributed to a decrease of energy transfer between P3OT molecules leading to an emission through chains with smaller conjugation length. The extra emission was also separated from the others by Time Resolved Emission Spectroscopy due to the fact that its lifetime is longer than those of the other emissions. Balance control of the emission through PFO (blue), low conjugation chains of P3OT (green) and P3OT aggregates (red) was possible changing the solvent and the way to prepare samples, that causes a greater or lesser amount of β phase in PFO. The study of the energy processes involved was also performed.