Rational Rigid-Core Design Realizes Efficient and Color-Pure Sky-Blue MR-TADF Emission in Boron-Nitrogen
Thamodharan Viswanathan1, Sabyasachi Maity1, Upasana Deori1
1Materials Research Centre, Indian Institute of Science, Bengaluru, Karnataka, India.
Abstract:
In this work, we report the strategic incorporation of a rigid 14H-dibenzo[a,j]xanthene (DBX) core into the BCz-BN framework, leading to the development of a novel DBX-BCz-BN multi-resonance (MR) thermally activated delayed fluorescence (TADF) emitter. This structural modification preserves the sky-blue emission color while substantially narrowing the emission profile, reducing the full width at half maximum (FWHM) to 17 nm. In addition, the singlet-triplet energy gap (ΔEST) is lowered from 0.17 eV for BCz-BN to 0.06 eV, thereby promoting more efficient reverse intersystem crossing (RISC) and improved exciton harvesting. As a result, the corresponding OLED device based on DBX-BCz-BN exhibits an external quantum efficiency (EQE) of 22.2%, while maintaining the same emission color. These results demonstrate that rigid-core engineering via DBX incorporation is an effective strategy for achieving narrowband, efficient, and color-pure sky-blue TADF emitters.
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