On the origin of excimer emission in electroluminescence and photoluminescence spectra of polyfluorenes

Enhancement of efficiency of multilayer polymer light-emitting diodes by inserting blocking layers

“…Sakamoto et al [25] reported that four PFO emission peaks have been measured at wavelengths of 432, 456, 491, and 527 nm. The shorter emission wavelengths were attributed to the vibronic levels of a single electronic excitation; while the broad unstructured emission band at wavelengths longer than 480 nm was attributed to the excimer emission [21,26]. The lower energy transition of excimer emission becomes more significant when the emitter is prepared from a thin film to a multilayer EL device [27].…”

New fluorene‐based copolymers containing oxadiazole pendant groups: Synthesis, characterization, and polymer stability

“…Homopolymers and copolymers, based on fluorene, represent a promising group of blue‐emitting materials because of their high fluorescence efficiency in the solid state, relatively high chemical stability of polymer main chains, and facile functionalization of fluorene units in the C‐9 position 6–8. However, these polymers suffer from a tendency to exhibit undesired red‐shifted emission, which has been ascribed to the following: (i) the emission of exciplexes formed by the excitation of aggregated monomeric units,9 (ii) the formation of excimers,10–14 (iii) the oxidation of fluorene monomeric units leading to a formation of keto defects, thus changing the photoluminescence spectrum,15–26 and (iv) the oxidation of other parts and/or crosslinking of polymer chains 27–31. According to the recent studies, the formation of keto defects seems to be the most plausible explanation for the undesired red‐shifted emission of PLEDs based on polyfluorenes 15–26…”