Solution Processable Deep-Blue OLEDs Based on Benzimidazole-TPA Conjugated through 9,9-Diethyl Fluorene (D-π-A) Luminophore with a Hybridized Local and Charge Transfer Excited State

Blue emitters with outstanding luminous performance must
be synthesized
for full-color organic light-emitting diode displays. The hybridized
local and charge transfer (HLCT) is a remarkable excited state that
combines the local and CT state to ensure a significant fluorescence
quantum yield. The ambition of this study is to implement a subtle
interpretation of photophysical and electroluminescence (EL) properties.
To understand more about the geometry and orientations, the density
functional theories were studied. Herein, we present a hybrid donor-π-acceptor
blue-emitting fluorophore with a twisted geometry, in which triphenylamine
(TPA) acts as a donor, 9,9 diethylfluorene acts as a spacer, and benzilimidazole
acts as an acceptor. The EL spectra of the device are very similar
to spectra of photoluminescence in the solution phase. Among all,
the best performing 15 wt % MCFBI-fl-TPA-based OLED device illustrates
a maximum luminance of 3290 cd/m2. The device shows 8.2
lm W–1 of power efficiency, 7.9 cd A–1 of current efficiency, and 3.5% of high external quantum efficiency
with (0.20, 0.23) of CIE coordinates of the device emitting blue color.