jo7b02127_si_001.pdf (1.46 MB)
Fine-Tuning of Photophysical and Electroluminescence Properties of Benzothiadiazole-Based Emitters by Methyl Substitution
journal contribution
posted on 2017-10-11, 00:00 authored by Ambika Pathak, K. R. Justin Thomas, Meenu Singh, Jwo-Huei JouNew
benzothiadiazole-based materials containing methyl substitution
are prepared and characterized as promising green/yellowish green
emitters for electroluminescent applications. The dyes exhibited shorter
wavelength absorption and emission when compared to nonmethylated
dyes. A dye containing methyl group on the donor side exhibited blue
shift in absorption and emission when compared to the analogous dye
containing methyl group away from donor. The steric effect exerted
by the methyl group is responsible for the nonplanar arrangement of
donor and acceptor, which inhibited the intramolecular charge transfer.
All the dyes displayed solvatochromism in the emission spectra characteristic
of hybridization of local and charge transfer excited states. Due
to the benefit of methyl group, the dyes restrained the formation
of aggregates in the solid state. Solution processed multilayered
OLED device were fabricated employing these compounds either as host
emitters or dopant emitters in suitable host matrix and exhibited
green/yellowish green electroluminescence with external quantum efficiency
as high as 4.6% (15.7 cd A–1).