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Highly Efficient Deep Blue Fluorescent Organic Light-Emitting Diodes Boosted by Thermally Activated Delayed Fluorescence Sensitization
journal contribution
posted on 2018-03-02, 00:00 authored by Dae Hyun Ahn, Jae Ho Jeong, Jie Song, Ju Young Lee, Jang Hyuk KwonHighly
efficient deep blue fluorescent material and various thermally activated
delayed fluorescent (TADF) blue sensitization materials were synthesized
for fluorescent deep blue organic light-emitting diodes (OLEDs). These
materials were designed and selected by considering efficient energy
transfer conditions (i.e., spectral overlap and quantum efficiency)
between sensitizer and acceptor. Energy transfer process from TADF
host sensitizers to deep blue fluorescent emitter has been investigated
by measuring the energy transfer rate. Measured energy transfer rate
was to be 1.24 × 1010 s–1 (mol/dm3)−1 for a prompt decay of fluorescence and
2.61 × 108 s–1 (mol/dm3)−1 for delayed fluorescence, which demonstrated
the efficient energy transfer. Indeed, highly efficient deep blue
fluorescent OLEDs boosted by the TADF host-sensitization process were
successfully fabricated. The maximum external quantum efficiency was
19.0% with color coordinates of (0.14, 0.15) and 15.5% with color
coordinates of (0.15, 0.11) in the different host system. The efficiency
roll-off characteristic and device operating lifetime were also improved
by this efficient sensitization process.