Stable pure-blue polymer light-emitting devices based on β-phase poly(9,9-dioctylfluorene) induced by 1,2-dichloroethane

Thin films of β-phase poly(9,9-dioctylfluorene) (PFO) were realized by dipping amorphous-phase PFO thin films in 1,2-dichloroethane for several seconds. Absorption, photoluminescence, and electroluminescence spectra indicate that the β-phase is generated in the thin films. A stable pure-blue polymer light-emitting device based on the β-phase PFO film was fabricated. The efficiency of the device with the β-phase is increased to 2.53 cd/A, which is 3.3 times higher than that of the device with the amorphous phase. Moreover, it is found that the device with β-phase emission shows high color purity as well as stable spectra.