Highly Luminous Sky-Blue Organic Light-Emitting Diodes Based on the Bis[(1,2)(5,6)]indoloanthracene Emissive Layer

An
in-depth analysis of the electro-optical and light-emissive
properties was carried out with a new fused heteroacene, the bis­[(1,2)­(5,6)]­indoloanthracene.
The compound was synthesized in a straightforward bidirectional manner
from 1,4-dibromo-2,5-diodobenzene utilizing a reaction cascade of
isomerization and cyclization sequences. Bis­[(1,2)­(5,6)]­indoloanthracene
exhibits bright luminescence with high quantum yield in solution as
well as in the solid state. By using this novel semiconductor as active
layer, an efficient organic light-emitting diode (OLED) has been fabricated
for which its emission pattern resembles at least two emitters in
a single emissive region originated from the same molecule. One has
its origin from the single molecule and is similar to the luminescence
spectra in solution, whereas the other functions through the formation
of aggregates being similar to the emission pattern found with crystals
of bis­[(1,2)­(5,6)]­indoloanthracene. As a result, bright sky-blue OLEDs
with very high luminance exceeding 10 000 cd/m2 were
obtained. Such color pattern and performance have not previously been
observed with low molecular weight, electron-rich fused polycyclic
aromatic compounds and indicate a promising new class of materials
for development.