Fluorescence tuning with a single dye embedded in a polymer matrix and its Application on multicolor OLEDs

Abstract

The tuning of emission for (Z)-2-(4-bromophenyl)-3-(4-(diphenylamine)phenyl)acrylonitrile owing to solvatochromism and colloidal formation, was studied. Fluorescence emission from blue (485 nm) to orange (602 nm) was achieved by dissolving the compound in solvents with different polarities, as well as by embedding it in a polymer matrix. By changing the dye:matrix ratio, the fluorescence of films can be tuned from 483 up to 599 nm. Similarly, changes in emission were observed when water was added to the dye-THF solution owing to the formation of agglomerates. The emission color can be tuned to green, yellow, and orange in the function of the water volume added. The PVK:dye films were used as the active layer in the preparation of OLEDs. The devices electroluminescence wavelength was tuned only varying the PVK:dye ratio; this is a remarkable achievement because devices with multicolor emission can be prepared with only one dye. With ratios from 1:0.05 to 1:1, the electroluminescence wavelength was tuned from 515 up to 596 nm. The results indicate that for this compound, the formation of agglomerates leads to a shift in the emission wavelength, unlike the well-known phenomena: aggregation-caused quenching, aggregation-induced emission, or aggregation-enhanced emission.